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Terra Mission (EOS/AM-1)

Spacecraft    Launch    Mission Status    Sensor Complement    EOS    References

Terra (formerly known as EOS/AM-1) is a joint Earth observing mission within NASA's ESE (Earth Science Enterprise) program between the United States, Japan, and Canada. The US provided the spacecraft, the launch, and three instruments developed by NASA (CERES, MISR, MODIS). Japan provided ASTER and Canada MOPITT. The Terra spacecraft is considered the flagship of NASA's EOS (Earth Observing Satellite) program. In February 1999, the EOS/AM-1 satellite was renamed by NASA to "Terra". 1) 2) 3) 4)

The objective of the mission is to obtain information about the physical and radiative properties of clouds (ASTER, CERES, MISR, MODIS); air-land and air-sea exchanges of energy, carbon, and water (ASTER, MISR, MODIS); measurements of trace gases (MOPITT); and volcanology (ASTER, MISR, MODIS). The science objectives are:

• To provide the first global and seasonal measurements of the Earth system, including such critical functions as biological productivity of the land and oceans, snow and ice, surface temperature, clouds, water vapor, and land cover;

• To improve the ability to detect human impacts on the Earth system and climate, identify the "fingerprint" of human activity on climate, and predict climate change by using the new global observations in climate models;

• To help develop technologies for disaster prediction, characterization, and risk reduction from wildfires, volcanoes, floods, and droughts

• To start long-term monitoring of global climate change and environmental change.

Complemented by aircraft and ground-based measurements, Terra data will enable scientists to distinguish between natural and human-induced changes.

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Figure 1: Illustration of the Terra spacecraft (image credit: NASA)


Spacecraft:

Terra consists of a spacecraft bus built by Lockheed Martin Missiles and Space (LMMS) in Valley Forge, PA. The spacecraft is constructed with a truss-like primary structure built of graphite-epoxy tubular members. This lightweight structure provides the strength and stiffness needed to support the spacecraft throughout its various mission phases. The zenith face of the spacecraft is populated with equipment modules (EMs) housing the various spacecraft bus components. The EMs are sized and partitioned to facilitate pre-launch integration and test of the spacecraft.

EPS (Electrical Power Subsystem): A large single-wing solar array (size of 9 m x 5 m = 45 m2), deployed on the sunlit side of the spacecraft, maximizes both its power generation capability and the cold-space FOV (Field of View) available to instrument and equipment module radiators. The average power of the satellite is 2.53 kW provided by a GaAs/Ge solar array (max of 7.5 kW @ 120 V at BOL). The solar array is based on on a prototype lightweight flexible blanket solar array technology developed by TRW (use of single-junction GaAs/Ge photovoltaics). A coilable mast is used for the deployment of the solar array. The Terra spacecraft represents the first orbiting application of a 120 VDC high voltage spacecraft electrical power system implemented by NASA. A PDU (Power Distribution Unit) has been designed to provide 120 DC (±4%) under any load conditions. This regulated voltage, in turn, is achieved via a sequential shunt unit (SSU) and the 2 BCDUs. A NiH2 (nickel hydrogen) battery is used (54 cells series connected) to provide power during eclipse phases of the orbit. 5) 6) 7)

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Figure 2: Coilable mast deployer for the Terra solar array (image credit: NASA)

GN&C (Guidance Navigation and Control) subsystem: Terra is a three-axis stabilized design with a single rotating solar array. The GN&C subsystem is made up of sensors, actuators, an ACE (Attitude Control Electronics) unit, and software. A three-channel IRU (Inertial Reference Unit) determines body rates in all control modes. Solid-state star trackers provide fine attitude updates, processed by a Kalman filter to maintain precise 3-axis inertial knowledge. A 3-axis magnetometer senses the Earth's geomagnetic field, primarily for magnetic unloading of reaction wheels, but also as a sensor to determine an attitude failure during a deep space calibration maneuver. 8)

The backup sensors include an ESA (Earth Sensor Assembly) for roll and pitch sensing, and coarse sun sensors for pitch and yaw sensing of the sun line relative to the solar array. A fine sun sensor is used in the event that one star tracker fails or during the backup stellar acquisition mode. In addition to these sensors, a gyro-compassing computation is performed for backup yaw attitude determination.

A reaction wheel assembly provides primary attitude control. During normal mode, a wheel speed controller is available to bias the wheel speeds at a range that avoids zero rpm crossings (stagnation point). Magnetic torquer rods regulate the wheel momentum to < 25% capacity in four-wheel mode and < 50% capacity in the three-wheel mode (backup mode). Thrusters are used for attitude control during all velocity change maneuvers and for backup attitude control and wheel momentum unloading.

GN&C is a fault-tolerant system that includes an FDIR (Fault Detection, Isolation and Recovery) capability unique to each of the different operational control modes. If an attitude fault is detected, FDIR transfers all control functions to the ACE unit configured to use all redundant hardware. Once in safe mode, FDIR is disabled.

Sensor component

Units

Manufacturer/model

Mission heritage

Solid State Star Tracker (SSST)

2

BATC / CT-601

MSX, XTE

Earth Sensor Assembly) (ESA)

2

Ithaco / conical scanning

UARS

Coarse Sun Sensor (CSS)

2

Adcole / 42060

UARS

Fine Sun Sensor (FSS)

1

Adcole / 42070

TOPEX

Three Axis Magnetometer (TAM)

2

NASA/GSFC

EUVE, UARS

Inertial Reference Unit (IRU)

2

Kearfott / SKIRU-DII

XTE

 

 

 

 

Actuator component

Units

Manufacturer/model

Heritage

Reaction Wheel Assembly (RWA)

4

Honeywell / EOS-AM

Similar to EUVE

Magnetic Torquer Rod (MTR)

3

Ithaco / TR500CFR

EUVE

Attitude Control Thruster

6 (x 2)

Olin Aerospace (Primex)

 

Delta-v thruster

2 (x 2)

Olin Aerospace (Primex)

 

Table 1: Overview of GN&C sensors and actuators

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Figure 3: Artist' view of the Terra spacecraft in orbit (image credit: NASA)

The design life of the Terra spacecraft is six years. The spacecraft bus is of size of 6.8 m (length) x 3.5 m (diameter) and has a total launch mass of 5,190 kg. The total payload mass is 1155 kg.

RF communications: The primary Terra telemetry data transmissions are via TDRS (Tracking & Data Relay Satellite) system. A steerable HGA (High Gain Antenna) and associated electronics are mounted on a deployed boom extending from the zenith side of the spacecraft. This location maximizes the amount of time available for TDRS communications via this antenna without obstruction by other pads of the spacecraft. Emergency communication is done via the nadir or zenith omni antenna. Command and engineering telemetry data are transmitted in S-band. The science data recorded onboard are transmitted via Ku-band at 150 Mbit/s. The nominal mode of operation is to acquire two 12 minute TDRSS contacts per orbit. During each TDRSS contact, both S-band and Ku-band transmission is being used.

The average data rate of the payload is 18.545 Mbit/s (109 Mbit/s peak); onboard recorders for data collection of one orbit. Mission operations are performed at GSFC. 9)

Broadcast of data: Besides Ku-band and S-band communication, Terra is also capable of downlinking science data via X-band. The X-band communication can be operated in three different modes, Direct Broadcast (DB), Direct Downlink (DDL) and Direct Playback (DP). DB and DDL is used to directly transmit real-time MODIS and ASTER science data respectively to users.

The DAS (Direct Access System) provides a backup option for direct transmission in X-band. DAS supports transmission of data to ground stations of qualified EOS users around the world. These users fall into three categories:

- EOS team participants and interdisciplinary scientists

- International meteorological and environmental agencies

- International partners who require data from their EOS instruments

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Figure 4: The Terra spacecraft in the cleanroom of LMMS at Valley Forge (image credit: LMMS)

 

Launch: The launch of the Terra spacecraft took place on Dec. 18, 1999 from VAFB, CA, on an Atlas-Centaur IIAS rocket.

Orbit: Sun-synchronous circular orbit, altitude = 705 km, inclination = 98.5º, period = 99 minutes (16 orbits per day, 233 orbit repeat cycles). The descending nodal crossing is at 10:30 AM.

Orbit determination is performed by TONS (TDRS Onboard Navigation System) which estimates Terra's position and velocity, drag coefficient, and master oscillator frequency bias. TONS is updated by Doppler measurements at the spacecraft's receivers and provides the attitude control software with a desired pointing ephemeris. Ground-based orbital elements are uplinked daily for backup navigation.

As of March 1, 2001, the Landsat-7, EO-1, SAC-C and Terra satellites are flying the so-called "morning constellation" or "morning train" (a loose formation demonstration of a single virtual platform). There is 1 minute separation between Landsat-7 and EO-1, a 15 minute separation between EO-1 and SAC-C, and a 1 minute separation between SAC-C and Terra. The objective is to compare coincident observations (imagery) from various instruments (synergistic effects). 10)

Figure 5: NASA's Terra mission at 10 years on-orbit (video credit: NASA)

 


 

Mission status:

• March 12, 2019: Tropical Cyclone Idai is poised to move inland over East African countries that were already soaked by flooding rain from the same storm system earlier this month. 11)

- The storm system first developed as a tropical disturbance on March 3 and grew by March 5 into a tropical depression with winds measuring 30 knots. In the process, it dropped heavy rain on Mozambique and Malawi and spawned deadly floods. By March 11, the storm had tracked eastward into the warm channel between the coast of Africa and Madagascar, where it strengthened into an intense tropical cyclone.

- Now on a southwestward track, forecasts call for Idai to reach Mozambique by March 14-15, bringing a second round of wind and heavy rain to the region.

- "Several cyclones in the past have started over Mozambique and then moved over water and intensified into more organized systems, although this type of situation is not common," said Corene Matayas, a researcher at University of Florida who has studied cyclones in this area. It is relatively common, however, to see cyclone tracks in the Mozambique Channel that meander and loop, due to weak steering currents.

- Cyclones that form in the channel tend to be weaker than those that form over the Southwest Indian Ocean, north and east of Madagascar. But Matayas points out that regardless of where a cyclone forms, some have reached their highest intensity within a day before landfall. Tropical Cyclone Eline in February 2000, for example, passed over Madagascar and the Mozambique Channel, and then quickly intensified just before landfall in Mozambique.

- "Keys to intensification are warm ocean waters to sufficient depth, the absence of strong winds in the upper troposphere, and being contained inside of a moist air mass," Matayas said. "These conditions are all present right now."

- Most tropical cyclone activity in the Southwest Indian basin occurs between October and May, with activity peaking in mid-January and again in mid-February to early March. Idai is the seventh intense tropical cyclone of the basin's 2018-2019 season.

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Figure 6: MODIS on on NASA's Terra satellite acquired this image of the cyclone on March 12, 2019, as it spun across the Mozambique Channel. Around this time, the potent storm carried maximum sustained winds of about 90 knots (105 miles/165 kilometers per hour)—equivalent to a category 2 storm on the Saffir-Simpson wind scale (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kathryn Hansen)

• March 4, 2019: Unseasonably warm temperatures swept across the United Kingdom and much of Europe in February 2019. The month started with snow and freezing temperatures in the United Kingdom, but provisional statistics from the UK Met Office indicate February 2019 was the second warmest February on record for the country. England, Scotland, and Wales all recorded their warmest meteorological winter days and hottest February days since record-keeping began in 1910. 12)

- Kew Gardens in London recorded 21.2° Celsius (70.1° Fahrenheit) on February 26, a new record for the warmest winter day in the United Kingdom. Scotland experienced its warmest winter day with 18.3°C (64.9°F) at Aboyne, Aberdeenshire, on February 21. Wales also broke its existing record, reaching 20.8°C (69.4°C) in Porthmadog, Gywnedd, on February 26.

- The high temperatures were the product of a large area of high pressure that stalled and trapped warm air over Europe. The clear, dry conditions allowed more sunshine to warm the ground. (February 2019 was the second sunniest on record for the United Kingdom as a whole.) The high-pressure system also drew in warm air from the North Atlantic near the Canary Islands.

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Figure 7: The maps of Figures 7 and 8 show land surface temperature anomalies for February 11-25, 2019. Reds and oranges depict areas that were hotter than average for the same two-week period from 2000-2012; blues were colder than average. White pixels were normal, and gray pixels did not have enough data, most likely due to excessive cloud cover. This temperature anomaly map is based on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite (image credit: NASA Earth Observatory, image by Joshua Stevens, using data from the Level 1 and Atmospheres Active Distribution System (LAADS) and Land Atmosphere Near real-time Capability for EOS (LANCE), story by Kasha Patel)

Legend to Figure 7: The map depicts land surface temperatures (LSTs), not air temperatures. LSTs reflect how hot the surface of the Earth would feel to the touch and can sometimes be significantly hotter or cooler than air temperatures.

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Figure 8: While the UK was experiencing record-breaking warmth, increased temperatures spread across central and eastern Europe—so much that spring barley harvesting may start early. Forecasters say the weather over central Europe will be warmer and drier-than-normal through May (image credit: NASA Earth Observatory, image by Joshua Stevens, using data from the Level 1 and Atmospheres Active Distribution System (LAADS) and Land Atmosphere Near real-time Capability for EOS (LANCE), story by Kasha Patel)

• February 28, 2019: The 2015-2016 El Niño event brought weather conditions that triggered regional disease outbreaks throughout the world, according to a new NASA study that is the first to comprehensively assess the public health impacts of the major climate event on a global scale. 13)

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Figure 9: Increased sea surface temperatures in the equatorial Pacific Ocean characterizes an El Niño, which is followed by weather changes throughout the world (image credit: NASA Goddard's Scientific Visualization Studio)

- El Niño is an irregularly recurring climate pattern characterized by warmer than usual ocean temperatures in the equatorial Pacific, which creates a ripple effect of anticipated weather changes in far-spread regions of Earth. During the 2015-2016 event, changes in precipitation, land surface temperatures and vegetation created and facilitated conditions for transmission of diseases, resulting in an uptick in reported cases for plague and hantavirus in Colorado and New Mexico, cholera in Tanzania, and dengue fever in Brazil and Southeast Asia, among others.

- "The strength of this El Niño was among the top three of the last 50 years, and so the impact on weather and therefore diseases in these regions was especially pronounced," said lead author Assaf Anyamba, a research scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "By analyzing satellite data and modeling to track those climate anomalies, along with public health records, we were able to quantify that relationship."

- The study utilized a number of climate datasets, among them land surface temperature and vegetation data from the Moderate Resolution Imaging Spectroradiometer aboard NASA's Terra satellite, and NASA and National Oceanic and Atmospheric Administration precipitation datasets. The study was published on 13 February 2019 in the journal Nature Scientific Reports. 14)

- Based on monthly outbreak data from 2002 to 2016 in Colorado and New Mexico, reported cases of plague were at their highest in 2015, while the number of hantavirus cases reached their peak in 2016. The cause of the uptick in both potentially fatal diseases was an El Niño-driven increase in rainfall and milder temperatures over the American Southwest, which spurred vegetative growth, providing more food for rodents that carry hantavirus. A resulting rodent population explosion put them in more frequent contact with humans, who contract the potentially fatal disease mostly through fecal or urine contamination. As their rodent hosts proliferated, so did plague-carrying fleas.

- A continent away, in East Africa's Tanzania, the number of reported cases for cholera in 2015 and 2016 were the second and third highest, respectively, over an 18-year period from 2000 to 2017. Cholera is a potentially deadly bacterial infection of the small intestine that spreads through fecal contamination of food and water. Increased rainfall in East Africa during the El Niño allowed for sewage to contaminate local water sources, such as untreated drinking water. "Cholera doesn't flush out of the system quickly," Anyamba said, "so even though it was amplified in 2015-2016, it actually continued into 2017 and 2018. We're talking about a long-tailed, lasting peak."

- In Brazil and Southeast Asia, during the El Niño dengue fever proliferated. In Brazil the number of reported cases for the potentially deadly mosquito-borne disease in 2015 was the highest from 2000 to 2017. In Southeast Asia, namely Indonesia and Thailand, the number of reported cases, while relatively low for an El Niño year, was still higher than in neutral years. In both regions, the El Niño produced higher than normal land surface temperatures and therefore drier habitats, which drew mosquitoes into populated, urban areas containing the open water needed for laying eggs. As the air warmed, mosquitoes also grew hungrier and reached sexual maturity more quickly, resulting in an increase in mosquito bites.

Figure 10: How the 2015-2016 El Niño triggered outbreaks across the globe (video credit: NASA Goddard's Scientific Visualization Studio)

- The strong relationship between El Niño events and disease outbreaks underscores the importance of existing seasonal forecasts, said Anyamba, who has been involved with such work for the past 20 years through funding from the U.S. Department of Defense. Countries where these outbreaks occur, along with the United Nations' World Health Organization and Food and Agriculture Organization, can utilize these early warning forecasts to take preventive measures to minimize the spread of disease. Based on the forecast, the U.S. Department of Defense does pre-deployment planning, and the U.S. Department of Agriculture (USDA) takes measures to ensure the safety of imported goods.

- "Knowledge of the linkages between El Niño events and these important human and animal diseases generated by this study is critical to disease control and prevention, which will also mitigate globalization," said co-author Kenneth Linthicum, USDA center director at an entomology laboratory in Gainesville, Florida. He noted these data were used in 2016 to avert a Rift Valley fever outbreak in East Africa. "By vaccinating livestock, they likely prevented thousands of human cases and animal deaths."

- "This is a remarkable tool to help people prepare for impending disease events and take steps to prevent them," said co-author William Karesh, executive vice president for New York City-based public health and environmental nonprofit EcoHealth Alliance. "Vaccinations for humans and livestock, pest control programs, removing excess stagnant water — those are some actions that countries can take to minimize the impacts. But for many countries, in particular the agriculture sectors in Africa and Asia, these climate-weather forecasts are a new tool for them, so it may take time and dedicated resources for these kinds of practices to become more utilized."

- According to Anyamba, the major benefit of these seasonal forecasts is time. "A lot of diseases, particularly mosquito-borne epidemics, have a lag time of two to three months following these weather changes," he said. "So seasonal forecasting is actually very good, and the fact that they are updated every month means we can track conditions in different locations and prepare accordingly. It has the power to save lives."

• February 18, 2019: In Spanish, Sierra Nevada means "snowy mountain range." During the past few months, the range has certainly lived up to its name. After a dry spell in December, a succession of storms in January and February 2019 blanketed the range. 15)

- In many areas, snow reports have been coming in feet not inches. Back-to-back storms in February dropped eleven feet (3 meters) of snow on Mammoth Mountain—enough to make it the snowiest ski resort in the United States. More than 37 feet (11 meters) have fallen at the resort since the beginning of winter, and meteorologists are forecasting that yet another storm will bring snow this week.

- Statistics complied by the California Department of Water Resources indicate that the mountain range had a snow water equivalent that was 130 percent of normal as of February 11, 2019. It was just 44 percent of normal on Thanksgiving 2018. Last season, on February 15, 2018, snow cover was at a mere 21 percent of normal.

- Some of the snow has come courtesy of atmospheric rivers, a type of storm system known for transporting narrow, low-level plumes of moisture across long ocean distances and dumping tremendous amounts of precipitation on land.

- The condition of Sierra Nevada snowpack has consequences that go well beyond ski season. Spring and summer melt from the Sierra Nevada plays a crucial role in recharging California's reservoirs. Though conditions could change, California drought watchers are cautiously optimistic that the boost to the snowpack will insulate the state from drought this summer.

- The reservoirs are already in pretty good shape. Cal Water data show that most of the reservoirs are already more than half-full, and several have water levels that are above the historical average for the middle of February.

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Figure 11: A succession of storms in January and February dumped huge amounts of snow on the Sierra Nevada. The MODIS instrument on NASA's Terra satellite acquired these natural-color images of the Sierra Nevada on February 11, 2019, and February 15, 2018. In addition to the much more extensive snow cover in 2019, notice the greener landscape on the western slopes of the range (image credit: NASA Earth Observatory, images by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Adam Voiland)

• February 12, 2019: The world is literally a greener place than it was twenty years ago, and data from NASA satellites has revealed a counterintuitive source for much of this new foliage. A new study shows that China and India—the world's most populous countries—are leading the increase in greening on land. The effect comes mostly from ambitious tree-planting programs in China and intensive agriculture in both countries. 16)

- Ranga Myneni of Boston University and colleagues first detected the greening phenomenon in satellite data from the mid-1990s, but they did not know whether human activity was a chief cause. They then set out to track the total amount of Earth's land area covered by vegetation and how it changed over time.

- The research team found that global green leaf area has increased by 5 percent since the early 2000s, an area equivalent to all of the Amazon rainforests. At least 25 percent of that gain came in China. Overall, one-third of Earth's vegetated lands are greening, while 5 percent are growing browner. The study was published on February 11, 2019, in the journal Nature Sustainability. 17)

- "China and India account for one-third of the greening, but contain only 9 percent of the planet's land area covered in vegetation," said lead author Chi Chen of Boston University. "That is a surprising finding, considering the general notion of land degradation in populous countries from overexploitation."

- This study was made possible thanks to a two-decade-long data record from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA's Terra and Aqua satellites. An advantage of MODIS is the intensive coverage they provide in space and time: the sensors have captured up to four shots of nearly every place on Earth, every day, for the past 20 years.

- "This long-term data lets us dig deeper," said Rama Nemani, a research scientist at NASA's Ames Research Center and a co-author of the study. "When the greening of the Earth was first observed, we thought it was due to a warmer, wetter climate and fertilization from the added carbon dioxide in the atmosphere. Now with the MODIS data, we see that humans are also contributing."

- China's outsized contribution to the global greening trend comes in large part from its programs to conserve and expand forests (about 42 percent of the greening contribution). These programs were developed in an effort to reduce the effects of soil erosion, air pollution, and climate change.

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Figure 12: Over the last two decades, the Earth has seen an increase in foliage around the planet, measured in average leaf area per year on plants and trees. Data from NASA satellites shows that China and India are leading the increase in greening on land. The effect stems mainly from ambitious tree planting programs in China and intensive agriculture in both countries (image credit: NASA Earth Observatory, image by Joshua Stevens, using data courtesy of Chen et al., (2019). Story by Abby Tabor, NASA Ames Research Center, with Mike Carlowicz, Earth Observatory)

- Another 32 percent of the greening change in China, and 82 percent in India, comes from intensive cultivation of food crops. The land area used to grow crops in China and India has not changed much since the early 2000s. Yet both countries have greatly increased both their annual total green leaf area and their food production in order to feed their large populations. The agricultural greening was achieved through multiple cropping practices, whereby a field is replanted to produce another harvest several times a year. Production of grains, vegetables, fruits and more have increased by 35 to 40 percent since 2000.

- How the greening trend may change in the future depends on numerous factors. For example, increased food production in India is facilitated by groundwater irrigation. If the groundwater is depleted, this trend may change. The researchers also pointed out that the gain in greenness around the world does not necessarily offset the loss of natural vegetation in tropical regions such as Brazil and Indonesia. There are consequences for sustainability and biodiversity in those ecosystems beyond the simple greenness of the landscape.

- Nemani sees a positive message in the new findings. "Once people realize there is a problem, they tend to fix it," he said. "In the 1970s and 80s in India and China, the situation around vegetation loss was not good. In the 1990s, people realized it, and today things have improved. Humans are incredibly resilient. That's what we see in the satellite data."

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Figure 13: This map shows the increase or decrease in green vegetation—measured in average leaf area per year—in different regions of the world between 2000 and 2017. Note that the maps of Figures 12 and 13 are not measuring the overall greenness, which explains why the Amazon and eastern North America do not stand out, among other forested areas (image credit: NASA Earth Observatory, image by Joshua Stevens, using data courtesy of Chen et al., (2019). Story by Abby Tabor, NASA Ames Research Center, with Mike Carlowicz, Earth Observatory)

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Figure 14: Ambitious tree-planting programs and intensified agriculture have led to more land area covered in vegetation ((image credit: NASA Earth Observatory, image by Joshua Stevens, using data courtesy of Chen et al., (2019). Story by Abby Tabor, NASA Ames Research Center, with Mike Carlowicz, Earth Observatory)

• February 6, 2019: For the ranchers and soybean farmers of northwestern Argentina, January 2019 was a remarkably wet month. 18)

- After several weeks of storms that dropped about five times more rain than usual, floods have inundated millions of hectares of farmland, forced thousands of people to evacuate, and even turned some unsuspecting cattle into swimmers. Some areas received a year's worth of rain in the first two weeks of January, according to the Buenos Aires Times.

- The flooding has caused more than $2 billion in agricultural damage, according to one estimate. That makes it Argentina's second-most-expensive flood on record.

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Figure 15: This MODIS image shows the flooding along the Paraná River on 4 February 2019, composed in false color, using a combination of infrared and visible light (MODIS bands 7-2-1). Flood water appears black; vegetation is bright green (image credit: NASA Earth Observatory image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Adam Voiland)

• February 1, 2019: While much of North America is enduring exceptionally cold winter temperatures, Australia is coping with all-time record summer heat. 19)

- An unusual, prolonged period of heatwaves has been sweeping over Australia for most of the summer, including the country's hottest December on record. The intense heat has caused numerous deaths, power outages, and severe fires. The heatwaves started in late November when Queensland saw record-breaking temperatures on the north tropical and central coasts.

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Figure 16: This map shows land surface temperature anomalies from January 14-28, 2019. Red colors depict areas that were hotter than average for the same two-week period from 2000-2012; blues were colder than average. White pixels were normal, and gray pixels did not have enough data, most likely due to excessive cloud cover. This temperature anomaly map is based on data from MODIS on NASA's Terra satellite (image credit: NASA Earth Observatory, image by Lauren Dauphin, using data from the Level 1 and Atmospheres Active Distribution System (LAADS) and Land Atmosphere Near real-time Capability for EOS (LANCE). Story by Kasha Patel)

- Note that the map depicts LSTs (Land Surface Temperatures), not air temperatures. LSTs reflect how hot the surface of the Earth would feel to the touch and can sometimes be significantly hotter or cooler than air temperatures. (To learn more about land surface temperatures and air temperatures, read: Where is the Hottest Place on Earth?).

- The summer of 2018-19 has brought seven of the ten hottest days on record for Australia. The most potent heatwave so far occurred from January 11-18, when nationally averaged mean temperatures exceeded 40°C (104°F) for five days in a row. Nationally, January 15th ranked as the second-warmest day ever in Australia, falling 0.02°C short of the all-time record from January 2013. Adelaide recorded the hottest temperature for any Australian state capital in 80 years, reaching 46.4°C (116°F) on January 25.

- A few factors have contributed to the severe summer, starting with a dearth of strong weather fronts that would typically cool the country. In summer, sunlight heats the Australian landmass more quickly than the surrounding ocean. This difference in heating usually draws in moist air over northern Australia, which gradually brings about westerly winds that bring in cooler and rainy conditions with the monsoon.

- But this summer the rains didn't develop. Weather patterns in northern Australia were largely static, providing no significant weather systems to clear out the persistent hot air mass. The city of Darwin usually experiences the beginning of the monsoon in late December, but as of January 22, rainy patterns still had not set in. Western Australia also experienced sparse thunderstorms and no monsoonal activity in December. Northwesterly winds and various weather systems dragged hot air east and south across the Northern Territory, South Australia, western Queensland, New South Wales, and Victoria.

- The increased temperatures are a continuation of a longer warming trend for Australia. Twenty of the warmest years on record have occurred in the past 22 years; the last four have been the hottest on record. Throughout 2018, maximum temperatures for each month were above the country's average.

• January 30, 2019: Desperately cold weather is now gripping the Midwest and Northern Plains of the United States, as well as interior Canada. The culprit is a familiar one: the polar vortex. 20)

- A large area of low pressure and extremely cold air usually swirls over the Arctic, with strong counter-clockwise winds that trap the cold around the Pole. But disturbances in the jet stream and the intrusion of warmer mid-latitude air masses can disturb this polar vortex and make it unstable, sending Arctic air south into middle latitudes.

- That has been the case in late January 2019. Forecasters are predicting that air temperatures in parts of the continental United States will drop to their lowest levels since at least 1994, with the potential to break all-time record lows for January 30 and 31. With clear skies, steady winds, and snow cover on the ground, at least 90 million Americans could experience temperatures at or below zero degrees Fahrenheit (-18° Celsius), according to the U.S. National Weather Service (NWS).

- Figure 17 is not a traditional forecast, but a reanalysis of model input fixed in time—a representation of atmospheric conditions near dawn on January 29, 2019. Measurements of temperature, moisture, wind speeds and directions, and other conditions are compiled from NASA satellites and other sources, and then added to the model to closely simulate observed reality. Note how some portions of the Arctic are close to the freezing point—significantly warmer than usual for the dark of mid-winter—while masses of cooler air plunge toward the interior of North America.

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Figure 17: This map shows air temperatures at 2 meters above ground at 09:00 Universal Time (4 a.m. Eastern Standard Time) on January 29, 2019, as represented by the Goddard Earth Observing System Model, Version 5. GEOS-5 is a global atmospheric model that uses mathematical equations run through a supercomputer to represent physical processes (image credit: NASA Earth Observatory, image by Joshua Stevens, using GEOS-5 data from the Global Modeling and Assimilation Office at NASA GSFC, Story by Michael Carlowicz)

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Figure 18: You can almost feel that cold in this natural-color image, acquired on January 27, 2019, by MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite. Cloud streets and lake-effect snow stretch across the scene, as frigid Arctic winds blew over the Great Lakes (image credit: NASA Earth Observatory, image by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Michael Carlowicz)

- NWS meteorologists predicted that steady northwest winds (10 to 20 miles per hour) were likely to add to the misery, causing dangerous wind chills below -40°F (-40°C) in portions of 12 states. A wind chill of -20°F can cause frostbite in as little as 30 minutes, according to the weather service.

- Meteorologists at The Washington Post pointed out that temperatures on 31 January 2019, in the Midwestern U.S. will be likely colder than those on the North Slope of Alaska.

Figure 19: Animated AIRS image of the polar vortex moving from Central Canada into the U.S. Midwest from January 20 through January 29. The illustration shows temperatures at an altitude of about 300-500 m above the ground. The lowest temperatures are shown in purple and blue and range from -40 degrees Fahrenheit (also -40 degrees Celsius) to -10ºF (-23ºC). As the data series progresses, you can see how the coldest purple areas of the air mass scoop down into the U.S. (image credit: NASA/JPL-Caltech AIRS Project) 21)

• December 23, 2018: Spring and summer are bloom times for plants on land; they are also bloom times for plant-like organisms in the ocean. Fueled by the abundant sunshine of midsummer, phytoplankton were recently spied blooming off the coast of Argentina. 22)

- The plant-like floating organisms of Figure 20 form the center of the ocean food web, becoming food for everything from microscopic animals (zooplankton) to fish to whales. They are key producers of the oxygen that makes the planet livable for humans and other creatures. And they are critical to the global carbon cycle, as they absorb carbon dioxide from the atmosphere and turn it into carbohydrates. When the phytoplankton die (or animals eat and excrete them), some of the remains sink, carrying carbon to the bottom of the ocean.

- The milky green and blue bloom developed along the continental shelf, where warmer, saltier coastal waters and currents from the subtropics meet the colder, fresher waters flowing from the south. Where these currents collide—known to oceanographers as a shelf-break front—turbulent eddies and swirls form, pulling nutrients up from the deep ocean.

- The aquamarine stripes and swirls are coccolithophores, a type of phytoplankton with microscopic calcite shells that can give water a chalky color. The various shades of green are probably a mix of diatoms, dinoflagellates, and other species. Previous ship-based studies of the region have shown that Emiliania huxleyi coccolithophores and Prorocentrum sp. dinoflagellates tend to dominate. Scientists are working to identify types of phytoplankton from satellite images; hyperspectral imagers planned for future satellite missions should make that easier.

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Figure 20: The MODIS instrument on NASA's Terra satellite captured a natural-color image (above left) of the bloom on December 17, 2018. The right image shows Terra observations of concentrations of chlorophyll-a, the pigment used by phytoplankton to harness sunlight and turn it into food (image credit: NASA Earth Observatory, image by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview, and NASA's OceanColor Web. Story by Mike Carlowicz)

• December 15, 2018: Though the United States and Cuba have operated in largely separate economic spheres for decades, they are only separated by 150 kilometers (90 miles). On December 2, 2018, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image of the narrow, watery boundaries that separate the United States, Cuba, and the Bahamas. 23)

- From space, the deep water of the Florida Strait appears dark blue in comparison to the shallower, turquoise water covering the Cay Sal Bank and Bahama Banks. Both of these platforms formed as carbonate minerals—produced by certain types of bacteria and sea organisms—were deposited on the ocean floor over millions of years.

- Undeveloped ecosystems (forests and wetlands) cover 53 percent of Cuba, according to an analysis of recent Landsat imagery. About 40 percent of the island's land surface is used for agriculture. Major crops include cassava, tobacco, grapefruit, and sugar. Reservoirs cover about 1 percent of the island's land surface, and cities cover less than 1 percent.

- Despite the patchwork of farmland and pastures, Cuba is known for having relatively large stretches of pristine mangrove forests and undisturbed coral reefs, beaches, and sea grass marshes.

- "Cuba is an ecological rarity in Latin America and the Caribbean region," said University of Vermont remote sensing scientist Gillian Galford in a 2018 report. "Its complex political and economic history shows limited disturbances, extinctions, pollution, and resource depletion."

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Figure 21: MODIS image of Cuba acquired on 2 December 2018. Civilization's footprint on this Caribbean island has been relatively light (image credit: NASA Earth Observatory image by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Adam Voiland)

• November 28, 2018: The 2018 fire season in California has been record-breaking. The Mendocino Complex in July was California's largest fire by burned area on record, destroying nearly half a million acres. The Camp Fire in November was the deadliest and most destructive in state history, completely wiping out the town of Paradise. 24)

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Figure 22: This image shows the charred land—known as a burn scar—from the Camp Fire, which has destroyed more than 18,000 structures and caused at least 85 deaths. The fire, which has burned more than 153,000 acres, is now fully contained, according to the California Department of Forestry and Fire Protection. This image was acquired by MODIS on NASA's Terra satellite on 25 November 2018 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kasha Patel)

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Figure 23: A wide view of Northern California, where burn scars from nine major 2018 fires are visible from space. The image was acquired by Terra MODIS on November 25, 2018 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kasha Patel)

- "Every year, we keep hearing fires labeled as ‘the biggest', ‘worst', and ‘deadliest'," said Amber Soja, a wildfire scientist at NASA's Langley Research Center. "We keep hearing that this is the ‘new normal.' Hopefully it's not true for long, but right now it is."

- California's fire activity in 2018 is part of a longer trend of larger and more frequent fires in the western United States. Of the total area burned in the West since 1950, 61 percent of it has occurred in the past two decades, according to Keith Weber, GIS Director at Idaho State University and principal investigator of the NASA project RECOVER. "The 2018 fire year is going to fit right in to what's been going on the last decade or two. In fact, it might be a taller spike in the overall trend."

- High temperatures, low relative humidity, high wind speed, and scarce precipitation have increased dryness and made live and dead vegetation in western forests easier to burn. "Those fire conditions all fall under weather and climate," said Soja. "The weather will change as Earth warms, and we're seeing that happen."

- Soja also noted that California had a really wet winter in 2017, which helped build up grass and brush in rural and forested areas. The vegetation was an abundant fuel source as California headed into the 2018 dry season, which was exceptionally dry and lasted into late October.

- As fires are becoming more numerous and frequent, NASA's Disasters Program has been working with disaster managers to respond to the blazes. For California's Camp Fire and Woolsey Fire, NASA scientists and satellite analysts have been producing maps and damage assessments of the burned areas, including identifying areas that will be more susceptible to landslides in the upcoming winter.

• November 13, 2018: California continues to be plagued by wildfires — including the Woolsey Fire near Los Angeles and the Camp Fire in Northern California, now one of the deadliest in the state's history. NASA satellites are observing these fires — and the damage they're leaving behind — from space. 25)

- The Advanced Rapid Imaging and Analysis (ARIA) team at NASA's Jet Propulsion Laboratory in Pasadena, California, produced new damage maps using synthetic aperture radar images from the Copernicus Sentinel-1 satellites. The map of Figure 24 shows areas likely damaged by the Woolsey Fire as of Sunday, Nov. 11. It covers an area of about 50 miles by 25 miles (80 km by 40 km) — framed by the red polygon. The color variation from yellow to red indicates increasing ground surface change, or damage.

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Figure 24: The ARIA (Advanced Rapid Imaging and Analysis) team at NASA/JPL in Pasadena, California, created these DPMs (Damage Proxy Maps) depicting areas in California likely damaged by the Woolsey and Camp Fires (image credit: NASA/JPL)

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Figure 25: This map shows damage from the Camp Fire in Northern California as of Saturday, Nov. 10. It depicts an area of about 55 miles by 48 miles (88 km by 77 km) and includes the city of Paradise, one of the most devastated areas. Like the previous map, red areas show the most severe surface change, or damage. The ARIA team compared the data for both images to the Google Crisismap for preliminary validation (image credit: NASA/JPL)

• On November 8, 2018, the Camp Fire erupted 90 miles (140 km) north of Sacramento, CA. As of 10 a.m. PST on Nov. 9, the fire had consumed 70,000 acres of land and was 5 percent contained, or surrounded by a barrier. 26)

- Strong winds pushed the fire to the south and southwest overnight, tripling its size and spreading smoke over the Sacramento Valley. The Moderate Resolution Imaging Spectrometer (MODIS) on NASA's Terra satellite captured the natural-color image (annotate above, unannotated at right) on Nov. 9. The High-Resolution Rapid Refresh Smoke model, using data from National Oceanic and Atmospheric Administration (NOAA) and NASA satellites, shows the smoke should continue to spread west. The image also shows two more fires in southern California, the Hill and Woolsey Fires.

- More than 2,000 personnel have been sent to fight the Camp Fire, which is predicted to be fully contained by Nov. 30. Firefighters are having difficulty containing it due to strong winds, which fan the flames and carry burning vegetation downwind. The area also has heavy and dry fuel loads, or flammable material.

- State and local officials have closed several major highways, including portions of Highway 191. They also ordered evacuations in several towns, including Concow and Paradise, where the fatal fire burned through the town.

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Figure 26: Annotated image of the Camp Fire in Northern California and the Hill and Woolsey fires in southern California, taken Nov. 9, 2018, by the MODIS instrument on NASA's Terra satellite (image credit: NASA Earth Observatory)

On 6 October 2018, NASA's Terra satellite completed 100,000 orbits around Earth. Terra joins a handful of satellites to mark this orbital milestone, including the ISS (International Space Station), ERBS (Earth's Radiation Budget Satellite), Landsat-5 and Landsat-7. Terra, which launched Dec. 18, 1999, is projected to continue operation into the 2020s. 27)

- The five scientific instruments aboard Terra provide long-term value for advancing scientific understanding of our planet — one of the longest running satellite climate data records — and yield immediate benefits in such areas as public health. For example, recently scientists analyzed 15 years of pollution data in California, collected by the MISR (Multi-angle Imaging Spectroradiometer) instrument, and discovered that the state's clean air programs have been successful in reducing particle pollution. More urgently, data from the ASTER (Advanced Spaceborne Thermal Emission and Reflection) radiometer and MISR provided crucial information about the air quality and land change conditions around Hawaii's erupting Kilauea volcano, informing critical public health and safety decisions.

- But just as a plane can't fly without a crew, the Terra satellite never could have provided these vital benefits to society for this long without decades of dedicated work by engineers and scientists.

- Completing more than 2.5 billion miles of flight around Earth over almost 19 years, by a satellite designed to operate for five years, does not happen unless a satellite is designed, constructed and operated with great care.

- "Multiple, different aspects in the team make it work," said Eric Moyer, deputy project manager ­– technical at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The Terra team includes flight operations, subsystem engineers, subject matter experts, the instrument teams and the science teams for each of the instruments. Overall it all has to be coordinated, so one activity doesn't negatively impact another instrument," said Moyer, who worked on Terra during construction and continues to be involved with its operations today.

- Dimitrios Mantziaras, Terra mission director at Goddard, summed up what it takes: "A well-built spacecraft, talented people running it and making great science products, with lots of people using the data, that's what has kept Terra running all these years."

- Designing a Pioneer: Terra was unique from the beginning. It was one of the first satellites to study Earth system science, and the first to look at land, water and the atmosphere at the same time. Unlike many previous, smaller satellites, Terra didn't have a previously launched satellite platform to build upon. It had to be designed from scratch.

- "Unlike the Landsat mission series, which continues to improve upon its original design, nothing like Terra had ever been built," said Dick Quinn, Terra's spacecraft manufacturing representative from Lockheed Martin, who still works part-time with the team responsible for Terra's continued flight.

- Terra was meant to be the first in a series of satellites, known as AM-1, 2 and 3, each with a design life of about five years. Instead, the mission team ended up designing a satellite that lasted longer than the combined design life of three generations of Terra satellites.

- Constructing and Operating a Solid Satellite: The built-in redundancies and flexibility of the satellite were put to the test in 2009, when a micrometeoroid struck a power cell, degrading the thermal control for the battery.

- "We had to change the way we manage the battery to keep it operating efficiently and keep it at the right temperature," said Jason Hendrickson, Terra flight systems manager at Goddard, who joined the team in 2013. To do this, the team used the charge and discharge cycle of the battery itself to generate the heat necessary to keep the battery operating. They have been finetuning this cycle ever since.

- Terra engineers and scientists continually plan for worst-case scenarios, anticipating problems that may never develop. "We are always thinking, if this were to fail, how are we going to respond?" Hendrickson said. "You can't just go to the garage and swap out parts."

- Not only does the team plan for many possible scenarios, but it also looks back at the response and figures out how it can be improved. However, most of the time, they don't have to wait for a system failure to practice contingency plans. For example, in 2017 the team executed the second lunar deep space calibration maneuver in Terra's lifetime. The satellite turned to look at deep space, instead of at Earth. "We had to take into account what would happen if the computer were to fail when we were pointed at deep space," Hendrickson said.

- The calibration maneuver was executed successfully and the team never had to conduct their contingency plan. The science gained from calibrating Terra's data against deep space allowed the scientists to improve the data collected by the ASTER instrument. ASTER, a collaborative instrument with Japan and the United States, is one of five instruments on Terra. It monitors volcanic eruptions, among many other objectives and provides high resolution imagery of locations all over the world.

- In addition to ASTER, the instruments on Terra make many contributions and benefit people worldwide:

a) The Moderate Imaging Spectroradiometer (MODIS) collects data on land cover, land and sea surface temperatures, aerosol particle properties and cloud cover changes. For example, MODIS data is used to protect people's lives and property through operations like MODIS rapid response, which monitors wildfires daily.

b) MISR continues to provide data useful for health researchers studying the effects of particulate matter on populations all over the world, as well as fundamental studies of how aerosol particles and clouds affect weather and climate and investigations of terrestrial ecology.

c) Measurements of Pollution in the Troposphere (MOPITT), a collaboration with the Canadian Space Agency, is used to study carbon monoxide in the atmosphere, an indicator of pollution concentrations, also a contributor to global health issues.

d) Clouds and Earth's Radiant Energy System (CERES) provides data on Earth's energy budget, helping monitor the outgoing reflected solar and emitted infrared radiation of the planet.

- The science teams for each instrument work with the operations and technical teams to ensure that the scientific data provided is accurate and useful to the researchers who access it.

- The data is free and is valued by people all over the world. Not only can it be accessed daily, there are over 240 direct broadcast sites, where data can be downloaded in near real-time, all over the world. Moyer said that one of the most rewarding parts of working with Terra is that "the science data is truly valued by people we don't even know. People all over the world."

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Figure 27: Terra's test team stands in front of the satellite during its construction and testing phase (image credit: NASA, Dick Quinn)

• September 13, 2018: NASA's Multi-angle Imaging SpectroRadiometer (MISR) passed over Hurricane Florence as it approached the eastern coast of the United States on Thursday, September 13, 2018. At the time the image was acquired, Florence was a large Category 2 storm and coastal areas were already being hit with tropical-storm-force winds. 28)

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Figure 28: These data were captured during Terra orbit 99670. The MISR instrument, flying onboard NASA's Terra satellite, carries nine cameras that observe Earth at different angles. It takes about seven minutes for all the cameras to observe the same location. This stereo anaglyph shows a 3D view of Florence. You will need red-blue 3D glasses, with the red lens placed over the left eye, to view the effect. The anaglyph shows the high clouds associated with strong thunderstorms in the eyewall of hurricane and individual strong thunderstorms in the outer rain bands. These smaller storms can sometimes spawn tornadoes (image credit: NASA/JPL).

• August 24, 2018: Instruments on NASA's Terra and Aqua satellites were watching as Hurricane Lane — a category 2 storm as of Friday, Aug. 24 — made its way toward Hawaii. 29)

- NASA's MISR (Multi-angle Imaging SpectroRadiometer) captured images of Lane on just before noon local time on 24 August. MISR, flying onboard NASA's Terra satellite, carries nine cameras that observe Earth at different angles. It takes approximately seven minutes for all the cameras to observe the same location, and the motion of the clouds during that time is used to compute the wind speed at the cloudtops.

- The image shows the storm as viewed by the central, downward-looking camera. Also included is a stereo anaglyph, which combines two of the MISR angles to show a three-dimensional view of Lane (Figure 29). The image has been rotated in such a way that north is at the bottom. You will need red-blue glasses to view the anaglyph (with the red lens placed over your left eye).

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Figure 29: Stereo anaglyph using MISR data. The image shows a 3D view of Hurricane Lane on August 24. Red-blue 3D glasses required (image credit: NASA/GSFC/LaRC/JPL-Caltech, MISR Team)

- NASA's AIRS (Atmospheric Infrared Sounder) captured Hurricane Lane when the Aqua satellite passed overhead on 22 and 23 August (Figure 30). The infrared imagery represents the temperatures of cloud tops and the ocean surface. Purple shows very cold clouds high in the atmosphere above the center of the hurricane, while blue and green show the warmer temperatures of lower clouds surrounding the storm center. The orange and red areas, away from the storm, have almost no clouds, and the ocean shines through. In the 22 August image, a prominent eye is also visible. No eye is visible on the Aug. 23 image, either because it was too small for AIRS to detect or it was covered by high, cold clouds.

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Figure 30: This image shows Hurricane Lane as observed by the AIRS instrument on NASA's Aqua satellite on Thursday, 23 August (image credit: NASA/JPL-Caltech)

• August 15, 2018: When lightning storms passed over the Canadian province of British Columbia in July and August 2018, they ignited several hundred fires in forests that were already primed to burn. Abnormally hot, dry weather had stressed vegetation and parched the soil. And infestations of mountain pine beetles had left many forests with large numbers of dead trees. 30)

- Plumes of wildfire smoke can have a significant impact on people and the environment. Small particles in smoke pose a health risk because they can easily enter the lungs and bloodstream. And dark particles in smoke can land on snow and ice and accelerate melting by absorbing heat and reducing the reflectivity of the surface.

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Figure 31: MODIS on Terra captured this image of British Columbia's smoky landscape on August 13, 2018. Some of the thickest smoke lingered in the valleys, but plumes had also spread well beyond the province into Washington state and deep into the U.S. Midwest (image credit: NASA Earth Observatory, image by Lauren Dauphin using MODIS data from LANCE/EOSDIS Rapid Response, story by Adam Voiland)

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Figure 32: OLI (Operational Land Imager) on Landsat-8 captured this natural-color image of smoke lingering in valleys near the snow-capped peaks of the Coast Mountains on August 7, 2018 (image credit: NASA Earth Observatory image by Lauren Dauphin using Landsat data from the U.S. Geological Survey, story by Adam Voiland)

• August 11, 2018: Every austral winter in the central Andes, fresh snowfall covers and fills the gaps between mountaintops that have more permanent snow and ice. The continuous strip of winter white is visible in this image, acquired on July 30, 2018, with the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite. 31)

- Not all parts of the mountain range—one of the longest in the world—see equal amounts of the seasonal white stuff. The Andes span about 7,200 kilometers (4,500 miles) along the western side of South America, passing through multiple climate regions from dry to wet. This image shows a part of the Andes in central Chile and Argentina that bridges the two climate zones.

- Research into snowfall patterns has found that the largest areas of snow cover have occurred in this central zone. Areas to the north tend to be limited by a drier climate, while areas to the south are limited by the range's lower elevations. In this image you can see the Aconcagua, the highest mountain in the Southern Hemisphere, rising 6,962 meters (22,841 feet) above sea level.

- In this part of the range, the west side tends to receive more precipitation during austral winter, from June through August, when moist air from the Pacific Ocean is carried inland by westerly winds. But winter storms that pass through—including one in early August—can deliver enough snow to fully blanket glaciers on both sides.

- The snowpack that accumulates in the mountains is the primary source of water for communities at lower altitudes. Streams deliver the melt water to populated areas of central-western Argentina and central Chile, where it is particularly important for cities' water supply, power generation, and agriculture. According to Gonzalo Barcaza of the General Water Directorate in Santiago, Chile, this winter has been drier than usual and follows nearly a decade of drought.

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Figure 33: MODIS image acquired on 30July 2018 showing the snow coverage in the Andes region (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from LANCE/EOSDIS Rapid Response, story by Kathryn Hansen)

• August 2018: The nearly 20 years of MODIS imagery is the longest continuous daily global satellite observation record of Earth ever compiled. As of June 2018, all daily global MODIS imagery dating back to the operational start of MODIS data collection in 2000 is available through NASA's (GIBS Global Imagery Browse Services). GIBS was established by NASA's Earth Observing System Data and Information System (EOSDIS) in 2011 and provides quick access to over 700 satellite imagery products covering every part of the world. 32)

- The Worldview tool from NASA's Earth Observing System Data and Information System (EOSDIS) provides the capability to interactively browse over 600 global, full-resolution satellite imagery layers and then download the underlying data. Many of the imagery layers are updated within three hours of observation, essentially showing the entire Earth as it looks "right now". This supports time-critical application areas such as wildfire management, air quality measurements, and flood monitoring. View current natural hazards and events using the Events tab which reveals a list of natural events, including wildfires, tropical storms, and volcanic eruptions. Animate the imagery over time. Arctic and Antarctic views of several products are also available for a "full globe" perspective. Browsing on tablet and smartphone devices is generally supported for mobile access to the imagery.

- Worldview uses NASA's GIBS (Global Imagery Browse Services) to rapidly retrieve its imagery for an interactive browsing experience. While Worldview uses OpenLayers as its mapping library, GIBS imagery can also be accessed from Google Earth, NASA WorldWind, and several other clients. We encourage interested developers to build their own clients or integrate NASA imagery into their existing ones using these services.

• July 31, 2018: The Carr Fire, which has been burning near Redding, California since July 23, spanned 110,154 acres (44,578 hectares) as of July 31 and was 27 percent contained. The Ferguson Fire, near Yosemite National Park, spanned 57,846 acres (23,409 hectares) as of July 31 and was 33 percent contained (Figure 34). 33)

- These data were acquired during Terra orbit 98973 and 99002. The smoke plume height calculation was performed using the MISR INteractive eXplorer (MINX) software tool, which is publicly available at https://github.com/nasa/MINX. The MISR Plume Height Project maintains a database of global smoke plume heights, accessible at https://www-misr.jpl.nasa.gov/getData/accessData/MisrMinxPlumes2/.

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Figure 34: The MISR (Multi-angle Imaging SpectroRadiometer) instrument on NASA's Terra satellite took these images of the Carr Fire (left) and the Ferguson Fire (right) on July 27 and July 29, respectively (image credit: NASA)

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Figure 35: Left: This image shows the Carr Fire near Redding California on July 27 as observed by NASA's MISR instrument. The angular information from MISR's images is used to calculate the height of the smoke plume. The results are superimposed on the image on the right (image credit: NASA)

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Figure 36: The left image shows the Ferguson Fire near Yosemite National Park on July 29 as observed by NASA's MISR instrument. The angular information from MISR's images is used to calculate the height of the smoke plume. The results are superimposed on the image on the right (image credit: NASA)

• July 26, 2018: Hawaii's Kilauea volcano continues to create new land as flows from fissure 8, one of the most active to break ground since the eruption began in early May, reach the ocean. The ASTER (Advanced Spaceborne Thermal Emission and Reflection) radiometer instrument on NASA's Terra satellite detected the lava flow of fissure 8 — which extends from Leilani Estates to the Pacific Ocean — on July 25. 34)

- With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of about 15 to 90 m, ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched Dec. 18, 1999, on Terra. The instrument was built by Japan's METI (Ministry of Economy, Trade and Industry). A joint U.S./Japan science team is responsible for validation and calibration of the instrument and data products.

- The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping and monitoring of dynamic conditions and temporal change. Example applications are monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

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Figure 37: In this image, vegetation is displayed in red, clouds are white and the hot lava flows, detected by ASTER's thermal infrared channels, are overlaid in yellow. The image covers an area of 15.3 x 18.6 kilometers (image credit: NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team)

• July 21, 2018: Scorching, dry conditions are spurring historic wildfire outbreaks across Sweden this summer. On July 19, 2018, more than 40 fires dotted the country, causing firefighters to scramble and hundreds of people to evacuate their homes. The Swedish government called for international assistance—the second time this summer—and received firefighting airplanes and helicopters from Italy and Norway. 35)

- The intense fires are unusual for this time of the year, as Sweden's summers are normally mild. In May 2018, several cities experienced their hottest May days in 150 years of recordkeeping. Temperatures cooled off in June, but returned to record highs in July, when Sweden's national weather agency issued a warning for extremely high temperatures. At the same time, Sweden has experienced very low rainfall this summer.

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Figure 38: This natural-color image was acquired by MODIS on NASA's Terra satellite on July 17, 2018. The largest fire was near Ljusdal, although Kårböle, Jämtland, and several towns have been evacuated due to fires. No fatalities have been reported so far. The Copernicus Atmosphere Monitoring Service forecast model shows an increase in fine particulate pollution above the fire-stricken areas this week (image credit: NASA Earth Observatory image by Lauren Dauphin and Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response and the Level 1 and Atmospheres Active Distribution System (LAADS). Story by Kasha Patel)

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Figure 39: This temperature anomaly map is based on data from MODIS on NASA's Terra satellite. It shows land surface temperatures from July 1-15, 2018, compared to the 2000–2015 average for the same two-week period. Red colors depict areas that were hotter than average; blues were colder than average. White pixels were normal, and gray pixels did not have enough data, most likely due to excessive cloud cover. Note that it depicts land surface temperatures, not air temperatures. Land surface temperatures reflect how hot the surface of the Earth would feel to the touch in a particular location. They can sometimes be significantly hotter or cooler than air temperatures (image credit: NASA Earth Observatory image by Lauren Dauphin and Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response and the Level 1 and Atmospheres Active Distribution System (LAADS). Story by Kasha Patel)

- The hot, dry conditions helped create the severe fire risk for the Sweden. As of July 20, Sweden has over 10,000 hectares of burned land, which is nearly 24 times higher than the amount of burned land averaged over 2008-2017, according to the Copernicus Emergency Management Service.

- High temperatures and wildfires are also hitting neighboring countries and as far north as the Arctic circle. All-time high temperatures were hit in 14 locations in Norway, including Troms county where temperatures hit 33°C, as the southern part of the country was peppered with fires in 100 localities last week. Northern Finland saw temperatures of 33°C on July 18, while wildfires also spread near the border of Finland and Russia (Figure 40).

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Figure 40: This natural-color image shows fires near the Russia-Finland border. The image was captured by MODIS on NASA's Aqua satellite on July 20, 2018 (image credit: NASA Earth Observatory image by Lauren Dauphin and Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response and the Level 1 and Atmospheres Active Distribution System (LAADS). Story by Kasha Patel)

• July 7, 2018: Northeast of Africa's Kalahari Desert and southeast of the Okavango Delta lies one of the largest salt pans in the world. It was once the site of one of the largest inland seas on Earth. 36)

- For much of the year, the salt pans glimmer in white, parched by the sun and the salt and allowing little more than algae to grow. But during the rainy season (roughly November to March), the area can be transformed into a crucial wetland. Water can flow in from the Boteti and Nata rivers, filling ephemeral ponds, watering holes, and shallow lakes and creating short-lived but abundant grasslands. The event draws migrating wildebeest and zebras, as well as the predators that hunt them. The waters fill with ducks, geese, pelicans, and flamingos—one of just two breeding spots in southern Africa for the long-legged birds.

- The pans are the salty remains of ancient Lake Makgadikgadi. Scientists estimate that the inland sea once spanned anywhere from 80,000 to 275,000 km2. The Okavango, Zambezi, and Cuando rivers likely emptied into this lake until tectonic shifts changed the elevation of the landscape and a changing climate dried up the rains.

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Figure 41: On June 10, 2018, the MODIS instrument on NASA's Terra satellite acquired this natural-color image of the Makgadikgadi Salt Pans. The collection of salt flats covers roughly 30,000 km2 amidst desert and dry savanna in Botswana. Located in Makgadikgadi National Park and Nxai Pan National Park, the salt pans are rivaled in extent only by the Salar de Uyuni in Bolivia (image credit: NASA Earth Observatory, image by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response, story by Mike Carlowicz)

• June 5, 2018: Powerful Earth-observing instruments aboard NASA's Terra and Aqua satellites, launched in 1999 and 2002, respectively, have observed nearly two decades of planetary change. Now, for the first time, all that imagery—from the first operational image to imagery acquired today—is available for exploration in Worldview. 37) 38)

Thanks to the efforts of several NASA teams, the public can now interactively browse all global imagery from the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument quickly and easily from the comfort of a home computer. All global MODIS imagery dating back to the operational start of MODIS in 2000 is available through NASA's GIBS (Global Imagery Browse Services) for viewing using NASA's Worldview application. And there's a lot to see.

This achievement is the result of more than a half-decade of work and represents the longest continuous daily global satellite observation record of Earth ever compiled. For researchers, the ability to rapidly access and explore all MODIS global imagery greatly improves their use of these data.

"In the '80s and '90s, if you wanted to look at, say, clouds off the coast of California, you had to figure out the time of year when it was best to look at these clouds, then place a data request for a specific window of days when you thought the satellite overflew the area," says Santiago Gassó, an associate research scientist with NASA's Goddard Earth Sciences Technology And Research program at Morgan State University, Baltimore. "You would get a physical tape with these images and have to put this into the processing system. Only then would you know if the image was usable. This process used to take from days to weeks. Now, you can look at images for days, weeks and even years in a matter of minutes in Worldview, immediately find the images you need, and download them for use. It's fantastic!"

Daily MODIS global images have been produced since the public debut of Worldview in 2012. But data users wanted more. "Users said to us, 'We know you have the source data available, and we'd like to see it as imagery in Worldview,'" says Ryan Boller, the EOSDIS data visualization lead and Worldview Project owner.

GIBS provides access to more than 600 satellite imagery products covering every part of the world. Worldview pulls imagery from GIBS and allows users to interactively overlay all of these data products on top of a MODIS global base map from Terra or Aqua. Worldview users can even create data animations at the touch of a button and easily share imagery. Both GIBS and Worldview are part of NASA's EOSDIS (Earth Observing System Data and Information System), which provides end-to-end capabilities for managing NASA Earth-observing data.

The completion of this effort gives NASA's worldwide audience the ability to interactively view their world their way and interactively explore almost 20 years of planetary change. As Boller observes, "To be able to go from the very start, from the very first image, to the present and move forward provides not only a sense of completeness, but also the potential for new discoveries."

Table 2: Interactively explore your world your way with nearly 20 years of MODIS global imagery and the EOSDIS Worldview data visualization application

• On May 28, 2018, a series of potent dust storms swept across Iran, Turkmenistan, Afghanistan, and Pakistan. Accuweather reported winds approaching hurricane-force of 110 km/hr—near the city of Zabol in eastern Iran. Visibility dropped to zero at several points during the storms that lasted up to 12 hours in some places. News media claimed that as many as 100 people were injured across the region. 39)

- Meteorologists noted that the late-May dust storms were "caused by a strong upper level storm system that tracked north of the region, bringing thunderstorms to Turkmenistan and northern Afghanistan, but just producing powerful winds in eastern Iran." SST (Sea Surface Temperatures) in the Arabian Sea have been about 1.5 to 2º C above normal in May, which could be contributing to the development of potent winds and storm fronts blowing across the Middle East and India this spring.

- Iran is mostly arid or semiarid, with deserts making up at least 25 million hectares (250,000 km2) of the country's area. That already dry landscape has been parched by drought over the past year. Iranian environmental officials recently reported that 18 wetlands have completely dried up in recent months, and another 24 are in critical condition. Lake Urmia has been affected by warmer weather and drier than normal conditions over the past few decades. Such conditions have increased the amount of sand and dust available to be picked up by strong winds.

- Several governments and international groups have been looking for solutions to ease the region's water and dust problems, which are partly due to drought and global warming, but also attributed by some scientists to uneven water management practices (irrigation, storage, treatment, and groundwater pumping). In the meantime, the Iranian government recently reported that it would be spreading petroleum-based mulch across 46,000 hectares of the desert this year in order to cut down on dust pollution.

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Figure 42: MODIS on NASA's Terra satellite acquired this image of the dust storms on May 28, 2018. Such storms, sometimes known as haboobs, are dramatic events associated with weather fronts, and they often appear as walls of sand and dust marching across the landscape. Like thunderstorms, haboobs tend to abrupt and short-lived (image credit: NASA Earth Observatory, image by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response, story by Mike Carlowicz)

• On May 3, 2018, a new eruption began at a fissure of the Kilauea volcano on the Island of Hawaii. Kilauea is the most active volcano in the world, having erupted almost continuously since 1983. Advancing lava and dangerous sulfur dioxide gas have forced thousands of residents in the neighborhood of Leilani Estates to evacuate. A number of homes have been destroyed, and no one can say how soon the eruption will abate and evacuees can return home. 40)

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Figure 43: On May 6, 2018, at approximately 11 a.m. local time, the MISR (Multi-angle Imaging SpectroRadiometer) instrument on the Terra satellite captured this view of the island as it passed overhead. Much of the island was shrouded by clouds, including the fissure on its eastern point. However, an eruption plume is visible streaming southwest over the ocean. The MISR instrument is unique in that it has nine cameras that view Earth at different angles: one pointing downward, four at various angles in the forward direction, and four in the backward direction. This image shows the view from one of MISR's forward-pointing cameras (60º), which shows the plume more distinctly than the near-vertical views (image credit: NASA)

- The information from the images acquired at different view angles is used to calculate the height of the plume, results of which are superimposed on the right-hand image. The top of the plume near the fissure is at about 2,000 m altitude, and the height of the plume decreases as it travels south and west. These relatively low altitudes mean that the ash and sulfur dioxide remained near the ground, which can cause health issues for people on the island downwind of the eruption. The "Ocean View" air quality monitor operated by the Clean Air Branch of the State of Hawaii Department of Health recorded a concentration of 18 µg/m3 of airborne particles less than 2.5 µm in diameter at 11 a.m. local time. This amount corresponds to an air quality rating of "moderate" and supports the MISR results indicating that ash was most likely present at ground level on this side of the island.

- These data were acquired during Terra orbit 97780. The smoke plume height calculation was performed using the MISR MINX (INteractive eXplorer) software tool, which is publicly available at https://github.com/nasa/MINX. The MISR Plume Height Project maintains a database of global smoke plume heights, accessible at https://www-misr.jpl.nasa.gov/getData/accessData/MisrMinxPlumes2/.

• May 07, 2018: Loktak Lake is not only the largest freshwater lake in northeast India, it is also home to unique floating islands called "phumdis." These circular landmasses are made of vegetation, soil, and organic matter (at different stages of decomposition) that has been thickened into a solid form. The islands have a spongy surface that feels like a trampoline. Like an iceberg, most of the mass of phumdis lies below the water surface. During the dry season, when water levels drop, the living roots of the islands can reach the lakebed and absorb nutrients. 41)

- Speckled across this Loktak Lake, the several thousand phumdis and its surrounding waters are vital for irrigation, drinking water, food supplies, thus the lake has been referred as the "lifeline of Manipur" state. Thousands of fishermen make their livelihood in the waters, catching about 1,500 tons of fish every year. Children and illiterate adults also attend a school located on one of the floating islands.

- The phumdis support around 200 species of aquatic plants and 400 species of animals, including the rare Indian python. The largest island is home to the Keibul Lamjao, the world's only floating national park. It serves as a habitat for the endangered brow-antlered sangai, or "dancing deer," whose hooves have adapted to the island's spongy ground. The park, covering 40 km2, was specifically created to preserve the deer, which were once thought to be extinct. The habitat is composed of floating meadows and a raised strip of hard ground that separates the park into northern and southern zones.

- The construction of the Ithai Dam in the 1980s — built to provide power for India's northeast states — has threatened the life of the islands. The dam south of Loktak Lake has caused water levels to remain high year-round, preventing the phumdis from sinking and reaching the lakebed for nutrients. As a result, the phumdis are slowly thinning and breaking apart.

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Figure 44: The satellite images of Loktak Lake (Figures 44 and 45) were acquired on March 19, 2018, by ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) on the Terra satellite (image credit: NASA Earth Observatory, images by Joshua Stevens, using data from NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team, story by Kasha Patel)

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Figure 45: Overview image of Loktak Lake in India (image creedit: NASA Earth Observatory)

• April 28, 2018: Following a late-spring snowstorm in the Upper Midwest, rapidly melting snow filled rivers and streams and sent suspended sediment swirling in shallow parts of the Great Lakes. 42)

- Sediment loads tend to be especially heavy in the western end of Lake Erie. Of all the Great Lakes, Erie usually has the most sediment loading because of extensive farmland and cities near its shores. Since it is also the shallowest of the lakes, winds and currents can easily stir up sediments (quartz sand and silt, as well as calcium carbonate from limestone) on the lake bottom. And farmland, particularly fields that lack winter cover crops, tends to give up large amounts of sediment to rivers and streams.

- The situation is similar around Saginaw Bay, part of Lake Huron. More than half of the land surrounding the bay is used for agriculture, so spring runoff generally carries very large amounts of sediment.

- Landsat-8 and Sentinel-2 recently captured higher-resolution images of sediment in Saginaw Bay as well.

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Figure 46: MODIS on NASA's Terra satellite captured this image on April 20, 2018. After the storm, bloated rivers and streams dumped sediment-rich water into the lakes. Brisk spring winds combined with lake currents to send tendrils of mud and other debris swirling into deeper, bluer waters (image credit: NASA Earth Observatory, image by Adam Voiland, using MODIS data from LANCE/EOSDIS Rapid Response, story by Adam Voiland)

• April 17, 2018: Crops have withered and ranchers are culling herds after an unusually dry growing season in a country that is among the world's top producers of soybeans and corn. Argentina's soy production is projected to decline 31 percent and corn by 20 percent in 2017–2018 compared to the prior growing season, according to the U.S. Foreign Agricultural Service. 43)

- The economic consequences of the drought have been significant. Since December 2017, corn prices in the U.S. have risen 14 percent, and soybean prices are up 8 percent. Losses in Argentina are expected to surpass $3.4 billion, making the drought the most expensive natural disaster in 2018 so far.

- MODIS is just one of several satellite instruments useful for monitoring drought (Figure 47). The soil moisture maps (Figure 48) were produced with data collected on April 3, 2017, (left) and April 6, 2018, (right) by NASA's SMAP (Soil Moisture Active Passive) satellite. SMAP carries a radiometer that measures soil moisture in the top 5 cm of the ground. Dark green and blue areas are progressively wetter.

- Despite the projected declines in Argentina's soy crop, an unusually big crop in Brazil should help keep the global supply of soy at very high levels.

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Figure 47: The MODIS instrument on NASA's Terra satellite captured these natural-color images of the flat, fertile Pampas region of central Argentina. The Pampas appeared lush and green in April 2017 (left) in contrast to the browner landscapes (right) visible one year later (image credit: NASA Earth Observatory, images by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response. Story by Adam Voiland)

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Figure 48: Soil moisture map comparison of Argentina acquired with SMAP on April 3, 2017 (left) and on April 6, 2018 (right), image credit: NASA Earth Observatory, images by Joshua Stevens, using soil moisture data courtesy of JPL and the SMAP Science Team

• March 29, 2018: Days of heavy rains drenched several watersheds in central and northern Queensland in early March 2018. Following the deluge, NASA satellites collected images of the pulse of water as it flowed south through braided rivers in Australia's Channel Country, a desert region known for becoming lush with greenery after floods. 44)

- The MODIS instrument on NASA's Terra and Aqua satellites captured this sequence of six images between March 11 and March 26, 2018. It shows the progress of water (light blue) on the Hamilton, Diamantina, and Thomson Rivers. The images use a combination of infrared and visible light to increase the contrast between water and land.

Figure 49: MODIS on Terra and Aqua acquired this sequence of images between 11-26 March 2018 (image credit: NASA Earth Observatory, images by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response. Story by Adam Voiland)

- These three rivers drain from far to the north into basins near the border with South Australia, where water spreads out in large, shallow lakes. The rivers flow south toward the lowest point in Australia—Lake Eyre—partly because coastal mountain ranges block routes to the sea. As of March 27, 2018, flood water on the Diamantina had flowed as far south as Betoota and had begun to trickle into Birdsville, a remote town on the edge of the Simpson Desert.

- Northern Queensland is still being hammered by heavy rain. As the remnants of a tropical cyclone passed over the region on March 27, some areas received up to 400 mm of rain, according to Australia's Bureau of Meteorology.

• March 10, 2018: In late February 2018, a series of rainstorms pounded the central United States, causing damaging flooding along the Ohio River and parts of the Mississippi. Weeks after the storms, the effects were still being felt as far away as Louisiana. That pulse of flood water traveled down the Mississippi River and, by early March, reached the Gulf of Mexico. 45)

- On March 8, the U.S. Army Corps of Engineers opened the Bonnet Carré Spillway, which diverts excess water from the Mississippi River and relieves pressure on levees downriver in New Orleans. It marks the 12th time that the spillway has been opened since the structure was completed in the early 1930s. "This was a big event, but on the scale of big events, it's a small one," said Alex Kolker, an associate professor with the Louisiana Universities Marine Consortium.

- Still, the flood was substantial enough to color coastal waters brown with suspended sediments. On March 4, 2018, MODIS on NASA's Terra satellite acquired this image of the sediment plume spilling into the Gulf of Mexico.

- According to Nan Walker, director of Earth Scan Laboratory at Louisiana State University, sediment plumes are visible almost every spring. "The biggest floods of the Mississippi River occur on average in March or April," she said, "depending upon the weather over the drainage basin."

- When sediment-laden floodwaters reach the mouth of the Mississippi, they can contribute to land building. That's important because the wetlands in the lower part of the Mississippi River delta, particularly around a sub-delta known as Bird's Foot, are some of the most rapidly sinking wetlands in the country.

- "In order to keep pace with subsidence, you need floods like this one to bring sediment to the mouth of the Mississippi," Kolker said. "Many restoration plans revolve around diverting the flow of the Mississippi River in order to recreate systems like Bird's Foot higher up in the river system. But you need a lot of data to make these decisions when dealing with such a large, complicated hydrological issue."

- Satellite data helps scientists understand the movement of sediment and freshwater into the Gulf. According to Kolker, MODIS is good at telling scientists how a plume gets redirected by winds and currents. It also improves the understanding of plume dynamics—that is, where fresh water, nutrients, and sediments end up.

- When this image was acquired, winds were blowing out of the southeast, pushing the plume of sediment and freshwater to the northwest almost to Grand Isle. "This is the time of year when shrimp are spawning in that bay," Kolker said. "Events like this one can impact their life cycle."

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Figure 50: On March 4, 2018, MODIS on NASA's Terra satellite acquired this image of the sediment plume spilling into the Gulf of Mexico (image credit: NASA Earth Observatory, image by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response, story by Kathryn Hansen with image interpretation by Nan Walker and Alex Kolker)

• February 26, 2018: As sea ice at far northern latitudes approached its annual maximum extent, MODIS on NASA's Terra satellite captured this natural-color image of sea ice and clouds off of Canada's Newfoundland and Labrador province. Though sea ice has been significantly below normal extent and thickness across much of the Arctic, the ice in the Labrador Sea has been relatively close to normal. 46)

- In this image, acquired by MODIS on February 18, 2018, the coastline, the sea ice edge, and offshore clouds all present a clear edge to distinguish one from the next. Ice hugs the coast, where it receives the full chilling effect of offshore winds, and the water is shallower and fresher than in the open sea. The swirl patterns on the eastern edges reveal areas where ice is new and has not yet consolidated into a solid sheet, so it is more susceptible to stirring by winds and by ocean eddies.

- The cloud streets to the right indicate strong and cold winds were blowing from west to east from the interior of Labrador. The gap between the ice and the cloud streets occurs because the cold winds need some "fetch" (a distance of open water) to pick up moisture for cloud formation.

- The Labrador Sea is a marginal sea that separates Arctic Canada and Greenland while connecting the North Atlantic Ocean to the Arctic Ocean by way of Baffin Bay and Davis Strait. The area is critical to the formation of cold, deep water masses that help drive circulation in a phenomenon known as "the great ocean conveyor belt."

- The western half of the Labrador Sea is typically covered with ice from December through late spring, though the extent varies considerably with local weather patterns from year to year. As of mid-February 2018, sea ice extent in this region appeared to be near or just above the long-term average, according to maps from NSIDC (National Snow and Ice Data Center). However, conditions in the rest of the Arctic have been grim this winter. In fact, Arctic sea ice reached a record low for the month of January, and conditions have not improved much in February. NSIDC reported Arctic sea ice extent to be 9.4 percent below the 1981–2010 average.

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Figure 51: This MODIS image was acquired on 18 Feb. 2018 showing the coastline of Newfoundland and Labrador, the sea ice edge, and offshore clouds all present a clear edge to distinguish one from the next (image credit: NASA Earth Observatory, image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response. Story by Mike Carlowicz, with image interpretation from Walt Meier, NSIDC, and Claire Parkinson, NASA/GSFC)

• February 21,2018: Indonesia's Mount Sinabung has been sporadically active since 2010, following four centuries of quiet. On February 19, 2018, the stratovolcano on the island of Sumatra erupted violently, spewing ash at least 5 to 7 km into the air over Indonesia. At 11:10 a.m. local time (04:10 Universal Time) on February 19, MODIS on NASA's Terra satellite captured a natural-color image of the eruption, just a few hours after it began. 47)

- According to reporting from the Associated Press, the erupting lava dome obliterated a chunk of the peak as it erupted. Plumes of hot gas and ash rode down the volcano's summit and spread out in a 5 km diameter, while ash falls were recorded as far away as the town of Lhokseumawe, some 260 km to the north.

- Villages were coated in ash, and airline pilots were given the highest alert for the region. Government officials handed out face masks to the citizens of the island and advised them to stay indoors due to the potentially dangerous air quality. As volcanologist and blogger Erik Klemetti put it: "breathing volcanic ash is a significant health hazard—the ash is really small shards of glass, so it can abrade your lungs and form a ‘cement.'"

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Figure 52: MODIS image on Terra, acquired on 19 Feb. 2018, showing the massive smoke-and-ash column of Mount Sinabung on the island of Sumatra (image credit: NASA Earth Observatory, images by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response, Story by Mike Carlowicz)

- The volcanic plume also contained sulfur dioxide (SO2), which can irritate the human nose and throat when breathed in. The gas reacts with water vapor in the atmosphere to produce acid rain, and it also can react with other gases to form aerosol particles that cause haze and, in extreme events, climate cooling. The map of Figure 53 shows concentrations of SO2 as detected at 1:20 p.m. local time (06:20 Universal Time) on February 19 by the Ozone Mapper Profiler Suite (OMPS) on the Suomi-NPP satellite. Maximum gas concentrations reached 140 Dobson Units.

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Figure 53: OMPS (Ozone Mapper Profiler Suite) on Suomi NPP observed the SO2 cloud of the Sinabung eruption, acquired on 19 Feb. 2018 (image credit: NASA Earth Observatory, images by Joshua Stevens, using OMPS data from the Goddard Earth Sciences Data and Information Services Center (GES DISC), Story by Mike Carlowicz)

- Other sensors on NASA satellites have also been monitoring Sinabung. According to data from CALIPSO, some debris and gas from the eruption appear to have risen 15 to 18 kilometers in the atmosphere.

• February 9, 2018: NASA's Terra satellite acquired this image of a dust storm from the Sahara blowing over the Mediterranean Sea toward southern Europe (Figure 54). 48)

- According to news reports, the dust was carried by winds known as the scirocco. (In North Africa, these same desert winds are known as "chrom" (hot) or "arifi" (thirsty). The warm, dry air mass begins over the Sahara, picks up moisture over the Mediterranean, and moves north toward areas of lower pressure along the coasts of Europe.

- The dust can be seen making its way toward Italy, and then continues to countries to the north (beyond this image). According to local news reports, the winds brought above average temperatures to Italy, while the sand increased the chance of rain. The fine sand particles can act as a "seed" on which water droplets can form fog or fall as rain. In Italy's coastal areas, cars were covered with a layer of dust.

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Figure 54: The MODIS instrument on Terra captured on 7 Feb. this image of a Sahara Storm carrying great amounts of sand north over the Mediterranean Sea (image credit: NASA Earth Observatory, images by Jeff Schmaltz, using MODIS data from LANCE/EOSDIS Rapid Response ,caption by Kathryn Hansen)

• January 28, 2018: Winter is a dusty season off the coast of North Africa. As temperatures drop and high pressure builds on the continent, strong winds known as the harmattan blow east across the Sahara. They pick up sand and dust from the desert and loft it over the ocean. In late January, MODIS on NASA's Terra satellite caught a glimpse of Saharan dust bathing the Cape Verde islands, which lie about 650 kilometers off the coast of Senegal. The images were acquired on January 22 and 23. 49)

- Note the wind shadows, wakes, and vortices—areas with less dust density—on the leeward side of the islands. Winds blowing from the northeast and east run into the high volcanic peaks of the islands, which block some of the dust and alter the air flow. Note, too, how much denser the dust plume grows on the second day.

- Hundreds of millions of tons of dust blow out of Africa every year, crossing the Atlantic all the way to the Caribbean and the Gulf of Mexico. This dust fertilizes the ocean with nutrients that can promote plankton growth, but it can also carry fungus and disease-causing microorganisms that damage coral reefs.

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Figure 55: MODIS image of Saharan dust, acquired on 22 Jan. 2018, bathing the Cape Verde islands - resulting in wakes and vortices on the leeward side of the islands (image credit: NASA Earth Observatory, images by Joshua Stevens and Jeff Schmaltz, using MODIS data from LANCE/EOSDIS Rapid Response. Story by Mike Carlowicz and Holli Riebeek)

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Figure 56: MODIS image of Saharan dust, acquired on 23 Jan. 2018, bathing the Cape Verde islands - Note, how much denser the dust plume grows on the second day (image credit: NASA Earth Observatory, images by Joshua Stevens and Jeff Schmaltz, using MODIS data from LANCE/EOSDIS Rapid Response. Story by Mike Carlowicz and Holli Riebeek)

• January 24, 2018: Heavy rains and swiftly warming temperatures followed a prolonged cold spell in the Northeastern U.S., leading to a long ice jam that clogged the Connecticut River. MODIS on NASA's Terra satellite collected natural-color (left) and false-color (right) images of the ice on January 18, 2018 (Figure 57). In the false-color image, ice appears light blue, and open water appears black. A second large jam is visible south of Haddam, Connecticut. 50)

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Figure 57: MODIS images of the Connecticut region acquired on 18 January 2018 (image credit: NASA Earth Observatory image by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response, caption by Adam Voiland)

- On the same day, the MSI (Multi Spectral Imager) on the European Space Agency's Sentinel-2 satellite acquired the data for a natural-color image (Figure 58) of the ice jam. Iced-over parts of the river are white; open water is green.

- The ice jam extended several miles upstream from Haddam. Much of it was made up of brash ice—a sturdy type that forms when thinner ice layers are pushed on top of each other and then frozen together by cold weather. Often brash ice on rivers includes tree limbs and other debris that make it difficult for ice cutters to break it.

- Three U.S. Coast Guard cutters capable of breaking ice are working in the area. Cheers went up from the shores of the river as the boats arrived and began to break up the jam on January 23, the Coast Guard tweeted.

- Ice jams can block the natural flow of rivers and cause water levels to rise behind them. On January 23, the river level was 2 m at Middle Haddam—high enough to cause minor flooding. National Weather Service forecasters expect the river to crest at 2.6 m on January 24.

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Figure 58: MSI natural-color image on Sentinel-2 of the Connecticut River ice jam captured on 18 Jan. 2018 (image credit: NASA Earth Observatory using modified Copernicus Sentinel data (2018) processed by the European Space Agency, caption by Adam Voiland)

• January 14, 2018: Sitting along the northwest rim of the Pacific Ring of Fire, Kamchatka is one of the most volcanically active parcels of land in the world. At least 300 volcanoes dot the peninsula, and at least 29 of them are active. 51)

- Two of those volcanoes were busily puffing away in early January 2018. MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite caught a glimpse of plumes rising from Shiveluch and Klyuchevskaya on January 9 (Figure 59). The plume from Shiveluch stretched for at least 100 km. Note the long shadows, which are caused by high peaks and thick clouds and the low, oblique angle of the Sun in the winter sky.

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Figure 59: The MODIS instrument on Terra observed the plumes rising from the Shiveluch and Klyuchevskaya volcanos on January 9 (image credit: NASA Earth Observatory, image by Joshua Stevens and Jeff Schmaltz, using MODIS data from LANCE/EOSDIS Rapid Response. Story by Michael Carlowicz)

- On January 10, OLI (Operational Land Imager) on Landsat-8 got clear, closeup views of the area around the Klyuchevskaya volocano (Figures 60 and 61).

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Figure 60: Detail OLI image of the Klyuchevskaya volcano, acquired on 10 January, 2018 (image credit: NASA Earth Observatory, image by Joshua Stevens and Jeff Schmaltz, using Landsat data from the USGS, Story by Michael Carlowicz)

- Shiveluch is one of the largest and most active volcanoes on the Kamchatka Peninsula, with at least 60 eruptions in the past 10,000 years. The current eruption has been ongoing since 1999. On January 10, 2018, the Kamchatka Volcanic Eruption Response Team reported that volcanic explosions had lofted ash 10 to 11 km into the atmosphere. The aviation threat level was briefly raised to code red, but was lowered to orange by the end of the day. Volcanic emissions can pose a hazard to airplane engines, which can stall or fail when choked with smoke and ash.

- By comparison, Klyuchevskaya was relatively docile on January 10, emitting a small plume of gas, steam, and ash. The volcano is the tallest and most active on the peninsula, and the latest eruption has been ongoing since August 2015. More than 100 eruptions have occurred at Klyuchevskaya in the past 3,000 years, with 12 eruptions since 2000.

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Figure 61: Overview image of OLI of the Klyuchevskaya volcano, acquired on 10 January, 2018 (image credit: NASA Earth Observatory, image by Joshua Stevens and Jeff Schmaltz, using Landsat data from the USGS, Story by Michael Carlowicz)

• January 9, 2018: After a powerful nor'easter dumped snow across a thousand miles of the U.S. East Coast, yet another blast of bitterly cold air spilled into the region and drove already low temperatures even lower. 52)

- Statisticians and meteorologists had plenty to tally as city after city broke daily low temperature records, but perhaps the most dramatic sign of the extreme cold emerged offshore. Many rivers, bays, and estuaries along the coast froze over, including some that only rarely have ice.

- MODIS (Moderate Resolution Imaging Spectroradiometer) on Terra captured this trio of images on January 7, 2018. Figure 62 shows ice in Delaware Bay—between New Jersey, Pennsylvania, and Delaware—and the northern part of the Chesapeake Bay between Maryland and Delaware. Figure 63 shows ice in the Albemarle Sound in North Carolina, and Figure 64 shows Rhode Island and southeastern Massachusetts.

- The U.S. Coast Guard warned mariners of icy conditions and started operations to break up ice in some areas. Basins and waterways that are shallow and less salty, such as coastal rivers and estuaries, tend to freeze before deeper, saltier water (while fresh water freezes at 32°F (0°C), seawater freezes at 28 °F.)

- On January 7, 2018, several cities experienced record low temperatures, according to the National Weather Service. Temperatures dropped to -20 degrees Fahrenheit (-29 Celsius) in Burlington, Vermont; -11°F (-24 ºC) in Portland, Maine; -2°F (-19ºC)in Boston, Massachusetts; -9°F (-22ºC) in Hartford, Connecticut; 2°F (-19ºC) in Wilmington, Delaware; 1°F (-17ºC) in Baltimore, Maryland; and 4°F (-15ºC) in Raleigh, North Carolina.

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Figure 62: MODIS image of Delaware Bay—between New Jersey, Pennsylvania, and Delaware acquired on 7 Jan. 2018 (image credit: NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response. Image cropping and caption by Adam Voiland)

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Figure 63: MODIS image of the Albemarle Sound in North Carolina acquired on 7 Jan. 2018 (image credit: NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response. Image cropping and caption by Adam Voiland)

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Figure 64: MODIS image of Rhode Island and southeastern Massachusetts, with ice in Buzzards Bay and Nantucket Sound, acquired on 7 Jan. 2018 (image credit: NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response. Image cropping and caption by Adam Voiland)

• January 4, 2018: It is frigid in much of Canada and the Midwestern and Eastern United States. Daily low-temperature records have dropped like snowflakes. New Year's polar plunges have been canceled due to the cold, and many people in the Southeast are in a battle to keep their pipes from freezing. 53)

- In the Western U.S., Alaska, Europe, and Asia—not so much. December and January have been abnormally warm for most of the world. People in California have been worrying about wildfires in what should be the wet season, and Alaskans are ice skating in T-shirts.

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Figure 65: MODIS land surface temperature map of North America, acquired in the period 26 Dec. 2017 to 2 Jan. 2018 (image credit: NASA Earth Observatory maps by Jesse Allen, based on MODIS land surface temperature data provided by the Land Processes Distributed Active Archive Center. Story by Adam Voiland)

- This temperature anomaly map is based on data from MODIS on NASA's Terra satellite. It shows land surface temperatures (LSTs) from December 26, 2017 to January 2, 2018, compared to the 2001–2010 average for the same eight-day period. Red colors depict areas that were hotter than average; blues were colder than average. White pixels were normal, and gray pixels did not have enough data, most likely due to excessive cloud cover. Note that it depicts land surface temperatures, not air temperatures. Land surface temperatures reflect how hot the surface of the Earth would feel to the touch in a particular location. They can sometimes be significantly hotter or cooler than air temperatures. (To learn more about LSTs and air temperatures, read: Where is the Hottest Place on Earth?)

- The map of North America underscores one of the realities of weather—when a cold snap hits one region, warmth often bakes another one. A giant meander (or Rossby wave) in the jet stream is the common thread that connects the warm weather west of the Rockies with the chill east of them. As the crest of a Rossby wave—a ridge—pushed unusually far toward Alaska in December, it dragged warm tropical air with it. In response, the other side of the wave—a trough—slid deep into the eastern United States, bringing pulses of dense, cold Arctic air south with it. The Rocky Mountains have boxed in much of the coldest, densest air, serving as a barrier between the cold and warm air masses.

- Even as the Eastern U.S. freezes, comparatively balmy conditions are dominating many other parts of the world. Europe, much of Asia, and the Middle East have been abnormally warm. In the southern hemisphere, Antarctica, eastern Australia, southern Africa, and the Horn of Africa have been warmer than usual, while the Amazon in South America, the Sahara in Africa, and western Australia were cool.

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Figure 66: MODIS land surface temperature map of the world, acquired in the period 26 Dec. 2017 to 2 Jan. 2018 (image credit: NASA Earth Observatory maps by Jesse Allen, based on MODIS land surface temperature data provided by the Land Processes Distributed Active Archive Center. Story by Adam Voiland)

• December 21, 2017: It is rare for large wildfires to burn in California in December, which is usually a wet month for the state. In most years, a few hundreds acres might burn. The 2006 Shekell fire in Ventura charred 13,600 acres, making it the largest December fire in the state between 2000 and 2016. — In 2017, the Thomas fire shattered the record for December and may soon eclipse the worst blaze in any month. After burning for 16 days, the massive fire had scorched 272,000 acres (110,000 hectares or 425 square miles) and was just 60 percent contained. That made it the second largest fire on record in California, trailing only the Cedar fire, which burned 273,246 acres in 2003. 54)

- OLI (Operational Land Imager) on Landsat-8 captured an image of the Thomas fire scar on December 18, 2017. The natural-color Landsat-8 image was draped over an ASTER-derived Global Digital Elevation Model, which shows the topography of the area. The fire raged first near Ventura, then burned the hills around communities of Ojai and Oak View. Firefighters put up a fierce fight and managed to prevent flames from descending into the valley towns. Flames then pushed west toward Summerland, Montecito, and Santa Barbara. As of December 20, the fire was still spreading along the northern edge of the burn scar.

- Authorities reported that more than 1,200 structures—most of them in Ventura County—have been destroyed. Several factors came together to make the blaze difficult to control. An usually wet winter and spring in early 2017 caused vegetation to flourish. Then the dry season turned out to be excessively dry, and rains also have been scarce in the typically wetter months of November and December. All of that vegetation dried out and was primed to burn. Once the fire started, warm temperatures and unusually fierce Santa Ana winds caused the fire to spread rapidly.

- After nearly two weeks of red flag conditions, a break in the weather has allowed firefighters to beat back the flames in the past few days. But fire officials still do not expect the Thomas fire to be completely contained until January 2018.

- After nearly two weeks of red flag conditions, a break in the weather has allowed firefighters to beat back the flames in the past few days. But fire officials still do not expect the Thomas fire to be completely contained until January 2018.

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Figure 67: OLI on Landsat-8 captured an image of the Thomas fire scar on December 18, 2017. The natural-color Landsat-8 image was draped over an ASTER-derived Global Digital Elevation Model which shows the topography of the area (image credit: NASA Earth Observatory image by Joshua Stevens, using Landsat data from the USGS and ASTER GDEM data from NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team, story by Adam Voiland)

• December 19, 2017: Peat is a soil-like mixture of partly decayed plant material that builds up in wetlands, swamps, and partly submerged landscapes. When it gets dried out or burned, it can be a significant source of greenhouse gases such as carbon dioxide and methane. 55)

- As the world continues to warm and human activities deplete and degrade wetlands and peatlands in many parts of the world, scientists and policymakers would like to have a better understanding of the volume of the world's peat deposits. However, past estimates have varied significantly.

- Earlier this year, researchers from the Sustainable Wetlands Adaptation and Mitigation Program offered new maps of peat extent and depth in the tropics. The scientists based their findings on a mixture of satellite, climate, and topographic data collected in 2011 that, when merged in a computer model, made it possible to generate better maps of the extent and depth of peatlands. The high resolution of the model meant they could identify peat-forming areas that were often omitted in previous mapping efforts—peat found under dense forest canopies, peat formed in areas that are only wet for part of the year, and other small deposits.

- Using their new approach, the researchers concluded that South America accounts for 46 percent of the global total of tropical peat and holds more than Asia (previously considered to be the largest source). Brazil, not Indonesia, led the world in tropical peatland area, with the Amazon Basin being the largest contributor of tropical peat. They also found new hot spots in Africa, with ten times more peat than was reported in previous estimates.

- The maps of Figures 68 and 69 show peatland depth in South America. Areas with the deepest peat are shown with dark orange. Thinner deposits are shown with lighter shades of orange and yellow. Most of the new stores of peat were found to be in relatively shallow deposits in the Amazon basin, particularly along the Rio Negro and Rio Branco.

- "The Rio Negro headwaters suffer from El Niño droughts, and large fires are known to affect the region. Some of these fires are likely affecting peat deposits, which would result in much larger greenhouse gas emission than previously thought for the region," said Rosa Maria Roman-Cuesta, a Center for International Forestry Research (CIFOR) scientist involved in the project.

- Areas mapped as having peat had to meet three conditions. They had to have enough water, according to rainfall and evapotranspiration data. A satellite sensor—the Moderate Resolution Imaging Spectroradiometer (MODIS)—had to observe wet surfaces for a prolonged period. And the terrain, based on information from the Shuttle Radar Topographic Mission, had to be able to retain water.

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Figure 68: Overview map showing the peatland deposits in South America, acquired in 2011 with MODIS on Terra and Aqua and with SRTM (Shuttle Radar Topography Mission), acquired in 2000 (image credit: NASA Earth Observatory, image by Jesse Allen using data from Gumbricht, T., et al. (2017), story by Adam Voiland) 56)

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Figure 69: Detail map of the Amazon basin, particularly along the Rio Negro and Rio Branco (image credit: NASA Earth Observatory, image by Jesse Allen using data from Gumbricht, T., et al. (2017), story by Adam Voiland)

• December 7, 2017: Thick smoke was streaming from several fires in southern California when the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite acquired a natural-color image in the afternoon on December 5, 2017. 57)

- The largest of the blazes—the fast-moving Thomas fire in Ventura County—had charred more than 65,000 acres (24,000 hectares or 94 square miles), according to Cal Fire. Smaller smoke plumes from the Creek and Rye fires are also visible.

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Figure 70: MODIS image of the Ventura County fire acquired on 5 Dec. 2017 (image credit: NASA Earth Observatory, images by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response, story by Adam Voiland)

- On the same day, the MSI (Multi Spectral Imager) on the Sentinel-2 satellite of ESA captured the data for a false-color image (Figure 71) of the burn scar. Active fires appear orange; the burn scar is brown. Unburned vegetation is green; developed areas are gray. The Sentinel-2 image is based on observations of visible, shortwave infrared, and near infrared light.

- The fires mainly affected a forested, hilly area north of Ventura, but flames have encroached into the northern edge of the city. On December 6, 2017, Cal Fire estimated that at least 12,000 structures were threatened by fire.

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Figure 71: MSI image of the Ventura County fire acquired on 5 Dec. 2017 (image credit: ESA, the image contains modified Copernicus Sentinel data (2017) processed by the European Space Agency)

- Powerful Santa Ana winds fanned the flames. Forecasters with the Los Angeles office of the National Weather Service warned that the region is in the midst of its strongest and longest Santa Ana wind event of the year. They issued red flag warnings for Los Angles and Ventura counties through December 8, noting that isolated wind gusts of 130 km/hr are possible.

- A prolonged spell of dry weather also primed the area for major fires. This week's winds follow nine of the driest consecutive months in Southern California history, NASA/JPL ( Jet Propulsion Laboratory) climatologist Bill Patzert told the Los Angeles Times. "Pile that onto the long drought of the past decade and a half, [and] we are in apocalyptic conditions," he said.

• December 5, 2017: Frigid air blowing from Eastern Russia created dramatic cloud formations over the Sea of Okhotsk in late November, 2017. The MODIS instrument aboard NASA's Terra satellite acquired a true-color image of the stunning scene on November 25 (Figure 72). 58)

- Snow covers the land of Eastern Russia in the west of this image, with a large bank of cloud overlying the land in the northwest. Long parallel rows of cumulus clouds blow off the snow-covered area and over the blue waters of the Sea of Okhotsk. These rows of cloud, known as "cloud streets" form as cold, dry air from the land blows across relatively warmer, much moister ocean water and create cylinders of spinning air. Where the air is rising, small clouds form. Where the air is descending, the skies are clear. The cloud streets align along the direction of the wind movement.

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Figure 72: MODIS on Terra captured this true-color image of a stunning cloud formation scene over the Sea of Okhotsk on 25 November, 2017 (image credit: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA/GSFC)

• November 28, 2017: The coastal waters along China's Jiangsu province are brown all year round due to the large volume of suspended sediment that flows out from the Yangtze, Yellow, and other rivers. 59)

- But every winter, an even larger tongue of sediment emerges over the Great Yangtze Bank and extends hundreds of kilometers into the East China Sea. These winter plumes are prominent features in satellite imagery for a few months, before fading away in the spring. MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite captured this natural-color image of a plume over the Great Yangtze Bank on November 9, 2017 (Figure 73).

- Remote sensing scientists find the feature perplexing and have advanced several theories about the causes. Some have argued that the plume is a product of currents moving sediment-laden river water eastward from the coast. Others have argued that it is caused by tides lifting up sediment that was deposited on the bottom of the Great Yangtze Bank hundreds of years ago.

- A new study in the Journal of Geophysical Research Oceans makes the case for the latter option. After gathering data on waves, sediments, and currents as observed in January 2016 (when the sediment plume was visible in satellite imagery), researchers developed a model that simulated conditions in this part of the ocean. They ran a series of computational experiments that showed that the energy of tides is strong enough to stir up bottom sediment from the Yangtze Bank.

- The tides do this all year round, the scientists think, but their modeling shows that the sediment can only rise up to the surface in the winter, when temperatures and salinities at the sea surface and bottom are roughly the same. In the summer, an influx of fresh water from the Yangtze, combined with heating of the surface layers of the sea, prevents vertical mixing and keeps the resuspended sediment in the depths.

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Figure 73: MODIS natural-color image of a plume over the Great Yangtze Bank on November 9, 2017 [image credit: NASA Earth Observatory image by Jesse Allen, using data from the Level 1 and Atmospheres Active Distribution System (LAADS). Story by Adam Voiland, with information from Zhifa Luo (East China Normal University)]

• October 11, 2017: Parts of northern California have been ravaged by intense and fast-burning wildfires that broke out on October 8, 2017. Blazes that started on a few hundred acres around Napa Valley were fanned by strong northeasterly winds, and by October 10, the 14 fires had consumed as much as 100,000 acres (150 square miles) of land. States of emergency have been declared in Napa, Sonoma, Yuba, and Mendocino counties, and thousands of people were asked to evacuate. The densely populated "wine country" is famous for its vineyards and wine-making operations and the tourists they attract. 60)

- In the late morning of October 9, MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite acquired a natural-color image of the smoke billowing from the fires (Figure 74).

- CalFire and local officials reported that at least 1,500 homes and businesses have been destroyed, and thousands more are being threatened. In some places, entire neighborhoods burned to the ground. Cellular and land-line phone communications have been lost in several areas. Authorities are still accounting for deaths and people reported missing. As of the morning of October 10, none of the fires were even partially contained, according to CalFire bulletins.

- While the causes of the fires are still under investigation, we do know what helped them spread quickly: abundant dried vegetation and seasonal wind patterns. "After more than a decade of drought, the fuel levels—dry brush and grasses—across California are exceptionally high," said William Patzert, a climatologist at NASA's Jet Propulsion Laboratory. "Last winter's welcome rains created more vegetation that, over the past six months, created more fuel."

- The fall season also typically brings hot, dry, and gusty winds. These Diablo winds are driven by atmospheric high-pressure systems over the Great Basin (mostly in Nevada). Winds blow from northeast to southwest over California's mountain ranges and down through the valleys and coastal regions. These downslope winds can quickly whip up a fire and carry burning embers to the next neighborhood or patch of woodland.

- "The simple formula is fuel-plus-meteorology-plus-ignition equals fire. The catalyst is people," Patzert added. "The fires erupted in areas where wildlands meet urban and suburban development. Californians have built in what are historical fire corridors, and these high-density developments are particularly vulnerable to fast-moving, destructive fires."

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Figure 74: MODIS on Terra acquired this image of the fire regions in northern California in the late morning of 9 October 2017 (image credit: NASA Earth Observatory, image by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response. Story by Mike Carlowicz)

• September 8, 2017: During the monsoon season, heavy rains regularly pummel South Asia. But the summer monsoon of 2017 was different. In August 2017, day-after-day of punishing rainfall caused catastrophic flooding in northern India, Nepal, and Bangladesh. 61)

- More than 40 million people in the three countries have been afflicted. Hundreds of villages have been submerged, and tens of thousands of homes have been destroyed. Millions of people are living in refugee camps, and vast tracts of farmland and grazing land has been inundated.

- One of the hardest hit areas is Bihar, a state in East India with a vast expanse of flat, fertile land. Flooding grew severe there after heavy rains on August 10, 2017. By September, nearly 17 million people in that state alone had been affected by floods, according to the United Nations Office for the Coordination of Humanitarian Affairs. Roughly 7,000 villages in Bihar have flooded and more than 700,000 people have been displaced.

- The images of Figures 75 and 76 show how Bihar's waterways changed through the monsoon.

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Figure 75: MODIS on the Terra satellite acquired this image of the Ganges, Koshi, and several other rivers on September 6, 2017, when flood water covered large swaths of the landscape (image credit: NASA Earth Observatory, images by Jesse Allen, using data from LAADS (Level 1 and Atmospheres Active Distribution System), story by Adam Voiland)

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Figure 76: This MODIS image on Terra shows the same area on May 24, 2017, before monsoon rains began (image credit: NASA Earth Observatory, images by Jesse Allen, using data from LANCE (Land Atmosphere Near real-time Capability for EOS), story by Adam Voiland)

• September 2, 2017: On August 31, 2017, MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite acquired a false-color image (top) of extensive flooding along the Texas coast and around the Houston metropolitan area in the aftermath of Hurricane Harvey. A second image shows the same area on August 20, four days before the storm made landfall. 62)

- Both images were made with a combination of visible and infrared light (MODIS bands 7-2-1) that highlights the presence of water on the ground. Water is generally dark blue or black in this type of image, but rivers also can appear light blue because they carry large amounts of suspended sediment. Turn on the image-comparison tool to spot areas that have been inundated by rainwater and coastal surges.

- On August 31, MODIS also captured natural-color images of the area. Note the tan and brown rivers and bays full of flood water from Harvey. Scientists and civil authorities have some concerns about urban and industrial pollutants being mixed into the floodwater runoff. Along the coast, muddy, sediment-laden waters from inland pour into the Gulf of Mexico, which also was churned up by the relentless storm.

- According to the National Weather Service, 51.88 inches (131.8 cm) of rain were recorded at Cedar Bayou, Texas—the highest rainfall total for any storm in recorded U.S. history. Meteorologists at The Washington Post noted that that is as much rain as usually falls in Houston in an entire year and in Los Angeles in four years. By most accounts, Harvey produced more cumulative rainfall than any storm in the U.S. meteorological record — as much as 24 trillion gallons of water (unofficial estimates).

- In addition to providing satellite imagery and data of the storm, NASA has started flying its UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar) aboard a Gulfstream III aircraft to collect high-resolution radar observations over rivers, flood plains, and critical infrastructure. That data can be compared and combined with SAR data from satellites such as the Sentinel- 1A and 1B missions of ESA.

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Figure 77: False-color image of MODIS, acquired on Aug. 31, 2017, showing extensive flooding along the Texas coast and around the Houston metropolitan area in the aftermath of Hurricane Harvey (image credit: NASA Earth Observatory, images by Jesse Allen, using data from LANCE (Land Atmosphere Near real-time Capability for EOS), Story by Mike Carlowicz)

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Figure 78: Detail image of the Houston region (image credit: NASA Earth Observatory, images by Jesse Allen, using data from LANCE (Land Atmosphere Near real-time Capability for EOS), Story by Mike Carlowicz)

• September 1, 2017: What remains of the large inland lake is a fraction of what it was in the 1950s and 60s. In those years, the government of the former Soviet Union diverted so much water from the Amu Darya and Syr Darya—the regions's two major rivers—to irrigate farmland, that it pushed the hydrologic system beyond the point of sustainability. During subsequent decades, the fourth largest lake in the world shrank to roughly a tenth of its former size and divided into several smaller bodies of water. 63)

- The image of Figure 79, captured by MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite, shows the Aral Sea in Central Asia on August 22, 2017. While the lake is much smaller in August 2017 than it was in the 1960s, some growth in the eastern lobe of the South Aral represents an improvement over August 2014, when that lobe was completely dry.

- Instead of pooling in one large basin, water flowing down the two rivers now ends up in either the North Aral Sea (fed by the Syr Darya) or the South Aral Sea (fed by Amu Darya). The Kok-Aral dike and dam, finished in 2005, separates the two water bodies and prevents flow out of the North Aral into the lower-elevation South Aral. The dam has actually led fisheries in the North Aral Sea to rebound, even as it has limited flow into the South basin.

- Managers use a sluice gate to let some water flow from the North Aral into the South Aral. During wet and snowy years, these releases are common; in dry years, they are rare. In 2017, heavy outflow from the North Aral in the winter, spring, and summer caused the eastern lobe of the South Aral to partially refill, explained Philip Micklin, a geographer emeritus from Western Michigan University.

- Large releases from the Toktogul Dam, a reservoir on a tributary of the Syr Darya, increased the flow of the Syr in the winter. In the spring, unusually warm temperatures melted enough snow pack and glacial ice in the Tien Shan to keep the river high. To a lesser degree, flow from the Amu Darya may have contributed to the partial replenishment of the eastern lobe in 2017 as well.

- The images of Figures 80 and 81 show the pathway water follows as it flows down the Syr Darya, into the North Aral Sea, and eventually the South Aral Sea. OLI (Operational Land Imager) on Landsat-8 collected the images on August 5, 2017. At the time, the sluice gates at the dam appeared to be open, and water was flowing past the Tsche-Bas Gulf and into the South Aral.

- "However, this year's events do not signal a restoration of the eastern lobe as a permanent feature," said Micklin. "Since the early 2000s, the eastern lobe revitalizes during heavy flow years and then dries completely, or nearly completely in low flow years. I see this process continuing for the foreseeable future."

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Figure 79: MODIS image of the Aral Sea in Russia, acquired on August 22, 2017 (image credit: NASA Earth Observatory image by Jesse Allen, using Terra MODIS data from the LANCE (Land Atmosphere Near real-time Capability for EOS), Story by Adam Voiland)

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Figure 80: This detail image the the Aral Sea was acquired on Aug. 5, 2017, with OLI on Landsat-8 (image credit: NASA Earth Observatory image by Jesse Allen,using Landsat-8 data from the USGS, Story by Adam Voiland)

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Figure 81: A further detail image of the North Aral Sea was acquired on Aug. 5, 2017 with OLI on Landsat-8. At the time, the sluice gates at the Kok-Aral Dam appeared to be open, and water was flowing past the Tsche-Bas Gulf and into the South Aral Sea ( (image credit: NASA Earth Observatory image by Jesse Allen,using Landsat-8 data from the USGS, Story by Adam Voiland)

• August 27,2017: Goldstrike mine in northeastern Nevada is one of the largest gold mines in the world. In 2016, the mine produced 1.1 million ounces of gold (corresponding to 34,100 kg). Only two other operations—the Grasberg mine in Indonesia and the Muruntau mine in Uzbekistan—produced more. 64)

- On September 25, 2016, ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) on NASA's Terra satellite captured this false-color image of the mine (Figure 82). Vegetation appears red. Water is dark blue. Bare rock appears in shades of brown and gray. The most noticeable feature is the Betze-Post open-pit mine, which is managed by Barrick Gold Corporation and has a depth of more than 500 meters. Smaller open-pit mines operated by other companies are also visible northwest and southeast of the Betze-Post pit.

- Trucks transport ore from the bottom of the pit to nearby processing facilities, where gold is concentrated and extracted. On average, there is roughly 0.1 ounce of gold per ton of ore. Processing typically involves crushing ore into powder, exposing it to high temperatures and pressures, and leaching material out of liquid slurries. Leftover slurry is stored in tailing ponds, where solids settle out. In addition to its large open-pit mine, Goldstrike has two underground mines that also produce ore.

- One of the key issues facing mines is water management. Open-pit mining requires pumping groundwater out of adjacent aquifers in order to prevent the pit from flooding. At Goldstrike, operators pump several thousand gallons of groundwater per minute to keep the water table below the level of the pit. Some of this water is used to process ore, but some of it gets used in other ways or pumped backed into the ground. For instance, the water used to irrigate the circular fields southwest of the Betze-Post pit comes from groundwater pumping related to the mining.

- While the company that operates Goldstrike mine maintains a network of monitoring wells and stream gages to track how mine activities are affecting the aquifer, it also has used InSAR (Interferometric Synthetic Aperture Radar) data from satellites as part of its monitoring efforts. Since each monitoring well can cost between $300,000 to $500,000, and InSAR offers a big-picture view of the aquifer, a satellite perspective can offer an effective way of monitoring subsidence, uplift, and other changes in the Earth's crust associated with groundwater pumping, the company noted. InSAR observations show subsidence in areas near the mines and uplift in areas southwest of the mines.

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Figure 82: ASTER image of the Goldstrike mine in northeastern Nevada, acquired on September 25, 2016 (NASA Earth Observatory, image by Jesse Allen, using data from NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team, story by Adam Voiland)

• August 19, 2017: NASA's Terra satellite was built to observe Earth, and for more than 17 years its imagers have looked downward for 24 hours a day, collecting images needed to study the planet's surface, oceans, and atmosphere. However, the satellite recently trained its eyes on a different celestial body. 65) 66)

- On August 5, 2017, Terra made a partial somersault, rotating its field of view away from Earth to briefly look at the Moon and deep space. This "lunar maneuver" was choreographed to allow the mission team to recalibrate Terra's imagers—MODIS (Moderate Resolution Imaging Spectroradiometer), ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer), and MISR (Multi-angle Imaging SpectroRadiometer). The Terra operations team last made such a maneuver in 2003.

- The orbital gymnastics are necessary for radiometric calibration; that is, making sure MODIS, MISR, and ASTER are properly recording the amount of light emitted and reflected by surfaces on Earth. In the harsh environment of space, satellite instruments are bombarded by high-energy particles, cosmic rays, and strong ultraviolet light, and this inevitably leads to degradation in the sensors over time. If changes in sensitivity are not properly accounted for, the images would start to make it appear as if Earth were growing darker or lighter—which would throw off scientific efforts to characterize air pollution, cloud cover, and other elements of the environment.

- The lunar surface provides a good eye test for the imagers. "The Moon is like a standard candle or lamp: the amount of energy from it is well known," said Kurt Thome, project scientist for Terra. "If you look at it periodically, it allows you to see if your instruments are changing over time."

- Since the Moon's surface brightness has been stable over the 17-year life of the mission—and, in fact, for thousands of years—the images of the lunar surface can be used as a standard for calibration. Terra can also observe the Moon without any atmospheric effects (such as turbulence, scattering, and absorption), which can add significant uncertainty in measured values.

- The image of Figure 83 was acquired by ASTER, while MODIS acquired the a further image. MODIS has actually been looking at the Moon monthly for nearly its entire mission, but MISR and ASTER do not have this capability or proper angles for such a view. "MODIS can peek out of the corner and get a view of the Moon," Thome said. "For MODIS, it has been a great way to understand the instrument over its lifetime and notice any changes."

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Figure 83: ASTER image of the moon acquired on August 6, 2017 (image credit: NASA, images by Michael Abrams, Abbey Nastan, and Jesse Allen)

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Figure 84: MISR images of the moon acquired on August 6, 2017 (image credit: NASA, images by Michael Abrams, Abbey Nastan, and Jesse Allen; Story by Tassia Owen, Abbey Nastan, and Michael Carlowicz)

- The nine images of Figure 84 come from MISR's nine imagers. The MISR operations team uses several methods to calibrate the data regularly, all of which involve imaging something with a known (or independently measured) brightness and correcting the images to match that brightness. Every month, MISR views two panels of a special material called Spectralon, which reflects sunlight in a very particular way. ASTER, meanwhile, views a set of lamps that light up its reflective bands. Periodically, this calibration is checked by a team on the ground that measures the brightness of a flat, uniformly colored surface on Earth (such as a dry desert lakebed) while MISR and ASTER fly overhead. The lunar maneuver offers a third opportunity to check the brightness calibration of MISR.

- When viewing Earth, MISR's cameras are fixed at nine different angles, with one (called An) pointed straight down, four pointed forwards (Af, Bf, Cf, and Df) and four angled backwards (Aa, Ba, Ca, and Da). The A, B, C, and D cameras have different focal lengths, with the most oblique (D) cameras having the longest focal lengths in order to preserve spatial resolution on the ground. During the lunar maneuver, however, the spacecraft rotated so that each camera saw the almost-full Moon straight on. This means that the different focal lengths produce images with different resolutions (D cameras produce the sharpest). These grayscale images were made with raw data from the red spectral band of each camera.

- After 17 years of collecting valuable data and dwindling fuel supplies, Terra is nearing the end of the mission, but not before it double-checks its data one last time. The lunar calibration is important not only for the accuracy of Terra's instruments, but also providing data that are used to calibrate other satellites (including weather).

• On July 6, 2017, MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite captured this image of sunglint on the waters around Crete and the Aegean Islands (Figure 85). 67)

- The phenomenon of sunglint is a matter of optics. Areas where the sea surface is smoother reflect more sunlight directly back to the satellite's imager. In contrast, areas of rougher water appear darker because light is scattered in many more directions.

- Dry, cool winds from the north, called the Etesian winds, are common over the Aegean Sea during summer. On the windward side of the islands, those winds pile up the water and disturb the surface. But as those air masses run into the islands and their rocky peaks, a "wind shadow" with much calmer winds (and seas) form on the leeward side of islands (in this case, the south sides). Darker areas amid the bright streaks could be the result of wind or water turbulence, or perhaps breaks in the wind-blocking land topography.

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Figure 85: Sunglint image of the Aegean islands, acquired with MODIS on July 6, 2017 (image credit: NASA Earth Observatory, image by Jeff Schmaltz, caption by Kathryn Hansen)

• July 5, 2017: Icy lakes and rivers make a significant footprint on the Arctic landscape. Though widely dispersed, lakes cover as much as 40 to 50 percent of the land in many parts of the Arctic, and seasonal lake and river ice covers roughly 2 percent of all of Earth's land surfaces. Since lakes and rivers have the highest evaporation rate of any surface in high latitudes, understanding and monitoring seasonal ice cover is critical to accurately forecasting the weather and understanding regional climate processes. 68)

- Lake and river ice also affects the people who live in the Arctic. Seasonal ice roads serve as a key transportation route for many communities. Ice jams can produce sudden and dangerous hazards to hydroelectric power facilities, infrastructure, and human settlements. Changing ice conditions make shipping and boating a challenge. And ice is involved in a range of hydrological processes that can affect the quality of drinking water.

- Nonetheless, lake and river ice generally gets the least attention from ice scientists. According to one analysis, scientists publish roughly 50 scientific articles related to lake or river ice each year. In comparison, well over 600 articles get written about glaciers, 500 about snow, 350 about sea ice, and 250 about permafrost.

- Satellites could help fill this gap. In fact, since the number of ground-based ice monitoring stations has declined since the 1980s, satellites offer one of the most promising means of monitoring lake and river ice over large areas, noted the authors of a book chapter about the state of lake and river ice research.

- On May 29, 2017, MODIS on NASA's Terra satellite captured this image of ice covering the Amundsen Gulf, Great Bear Lake, and numerous small lakes in the northern reaches of Canada's Northwest Territories and Nunavut. Sea ice generally forms in the Gulf of Amundsen in December or January and breaks up in June or July. Lake and river ice in this area follow roughly the same pattern, though shallow lakes freeze up earlier in the fall and melt earlier in the spring than larger, deeper lakes.

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Figure 86: On May 29, 2017, MODIS on NASA's Terra satellite captured this image of ice covering the Amundsen Gulf, Great Bear Lake, and numerous small lakes in the northern reaches of Canada's Northwest Territories and Nunavut (image credit: NASA Earth Observatory, image by Joshua Stevens, using MODIS data, story by Adam Voiland)

• May 14, 2017: Strong desert winds in mid-May 2017 lofted a huge dust plume from western Africa and carried it over the Atlantic Ocean. At 12:10 UTC on May 9, 2017, the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument on NASA's Terra satellite acquired this natural-color image of airborne sand and other aerosols. The plume stretched southwest to the Cabo Verde (Cape Verde) islands and beyond (Figure 87). 69)

- Africa is the world's largest source of dust to the atmosphere, contributing about 70 percent of the global total. Airborne mineral dust from the world's deserts delivers nutrients to the land and ocean, and affects the atmosphere and climate.

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Figure 87: A dust storm over western Africa acquired by MODIS on May 9, 2017 (image credit: NASA Earth Observatory, image by Jeff Schmaltz)

• April 30, 2017: It might look like something mysterious is happening in the waters off of Oman, but this dark, sinuous shape has a completely natural explanation. On April 11, 2017, the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite captured this natural-color image of the Arabian Sea (Figure 88). 70)

- Smooth water reflects sunlight like a mirror, particularly when viewed from above. Areas where that light is reflected by the water at the same angle that a satellite views it—when the Sun, the satellite, and the sea are lined up—appear brighter than surrounding areas. Viewed globally, sunglint shows up as long, linear streaks down the center of a swath of satellite data.

- This image shows a detailed view of sunglint in the Middle East. What's interesting is that the sunglint (bright area) is interrupted. Dark areas indicate surface waters that have been roughened by wind, causing sunlight to reflect in many directions. That means less light is reflected directly back toward the satellite. In this way, sunglint can be used to discern phenomena like wind patterns that are not directly visible in natural-color imagery.

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Figure 88: A large Sunglint region in the Arabian Sea interrupted by dark ares of wind-roughened surface waters. This image was acquired on April 11, 2017 with the MODIS instrument (image credit: NASA Earth Observatory, image by Jeff Schmaltz, text by Kathryn Hansen)

• March 28, 2017: A long-dormant volcano on Russia's Kamchatka Peninsula erupted in March 2017. Several satellites caught images of a thick, ash-laden plume trailing from Kambalny. MODIS on NASA's Terra satellite captured a natural-color image of the Kambalny Volcano and its plume on March 25, 2017, the day after it began to erupt. By 1:34 p.m. local time (01:34 Universal Time) that day, the plume stretched about 100 km to the southwest (Figure 89). A dark stain is visible to the west of the plume, where ash has covered the snow. By March 26, ash falls would cover the ground on both sides of the volcano. 71)

- OMI ( Ozone Monitoring Instrument) on on NASA's Aura satellite observed an airborne plume of sulfur dioxide (SO2) trailing south of Kamchatka on March 26 (Figure 90). "The higher SO2 amounts downwind could be due to multiple factors," said Simon Carn, an atmospheric scientist at Michigan Technological University, "including variable emissions at the volcano (such as an initial burst), increasing altitude of the plume downwind, or decreasing ash content downwind."

- Invisible to the human eye, SO2 can harm people as well as the environment. According to a recent study, volcanoes collectively emit 20 to 25 million tons of SO2 into the atmosphere per year.

- An alert from the Kamchatka Volcanic Eruption Response Team warned of sporadic ash plumes rising up to 8 km above sea level. The activity could affect international and low-flying aircraft in the region, the group said.

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Figure 89: MODIS image of the Kambalny ash plume, captured on March 26, 2017 (01:34 UTC), image credit: NASA Earth Observatory, image by Jeff Schmaltz and Joshua Stevens)

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Figure 90: OMI image of the Kambalny ash plume, acquired on March 26, 2017 (image credit: NASA Earth Observatory, image by Joshua Stevens)

• March 26, 2017: New Zealand's Tasman Glacier is a massive block of ice, but it is no bulwark. The longest glacier in the country is neither immovable nor permanent. Instead, it continues to shrink by the day. 72)

- In Figure 91, captured on December 30, 1990, by the TM (Thematic Mapper) on the Landsat-4 satellite, the Tasman Glacier stretched like a serpentine tongue. The image of Figure 92 was acquired on January 29, 2017, by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. Both false-color images use white to show frozen snow or ice, and blue for water. Brown represents bare ground, while red areas are covered in vegetation.

- In the 26 years between images, the ice has retreated an average of 180 meters per year, according to New Zealand's National Institute of Water and Atmospheric Research. Before 1973, Tasman Lake did not exist. In the past decade, it has swollen to a length of 7 km. The lake growth is a direct result of the glacier's decline. The Tasman Glacier retreated 4.5 km from 1990 to 2015 mostly through calving, according to Mauri Pelto, a glaciologist at Nichols College. Researchers have predicted the lake will "increase dramatically in the near future" as the glacier produces more meltwater. The footprint of nearby Murchison Lake (below Murchison Glacier) has also grown.

- New Zealand is home to more than 3,000 glaciers, many of which are in decline. The Tasman Glacier is one of several that drains into Lake Pukaki, which is used to generate hydroelectric power. Further downstream, the same water feeds the Waitaki River, a habitat to trout and salmon.

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Figure 91: Tasman Glacier false-color image of the Thematic Mapper instrument on Landsat-4, acquired on Dec. 30, 1990 (image credit: NASA Earth Observatory, image by Jesse Allen and Joshua Stevens)

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Figure 92: Tasman Glacier false-color image of JAXA's ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) on NASA's Terra satellite, acquired on Jan. 29, 2017 (image credit: NASA Earth Observatory, image by Jesse Allen and Joshua Stevens)

• February 21, 2017: Heat waves are not unusual in Australia. A subtropical belt of high pressure that flows over the continent regularly delivers pulses of hot, dry air to the surface in the summer. Yet even by Australian standards, the intense heat wave of February 2017 has been remarkable. 73)

- When a high-pressure system stalled over central Australia, extreme temperatures emerged first in South Australia and Victoria and then spread to New South Wales, Queensland, and Northern Territory. With overheated bats dropping from trees and bushfires burning out of control, temperatures smashed records in many areas.

- Figure 93 shows peak land surface temperatures between February 7 and 14, 2017, a period when some of the most extreme heating occurred. The map is based on data collected by MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite. Note that it depicts land surface temperatures, not air temperatures. Land surface temperatures reflect how hot the surface of the Earth would feel to the touch in a particular location. They can sometimes be significantly hotter or cooler than air temperatures.

- On February 12, 2017, air temperatures rose to 46.6°C in the coastal city of Port Macquarie, New South Wales, breaking the city's all-time record by 3.3º C. Two days earlier, the average maximum temperature across all of New South Wales hit a record-setting 42.4°C — a record that was broken the next day when it rose to 44.0°C. In some places, the duration of the heatwave has been noteworthy. Mungindi, a town on the border of Queensland and New South Wales, endured 52 days in a row when maximum temperatures exceeded 35°C — a record for New South Wales.

- Many scientists see exceptional heat waves like this as part of a broader trend. For instance, one study published by the Climate Council of Australia concluded that heatwaves — defined as at least three days of unusually high temperatures — grew significantly longer, more intense, and frequent between 1971 and 2008.

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Figure 93: MODIS on Terra acquired this image map of Australian land surface temperatures in the period Feb. 7-14, 2017 (image credit: NASA Earth Observatory, image by Jesse Allen, caption by Adam Voiland)

• February 12, 2017: Covering about 400,000 hectares (4000 km2) in Iran's Khuzestan province, the Shadegan wetlands are the largest in Iran (Figure 94). At their center is Shadegan Pond, a large but shallow body of water surrounded by a varied landscape of sugar plantations, date palm orchards, small towns, and military fortifications. The Karun River winds along its western edge. Fields of sugar cane stand northwest of it. The town of Shadegan—which is flanked by long, narrow orchards — lies to its east. 74)

- Environmental conditions at the wetlands vary throughout the year. In the fall and winter, rains in the Zagros Mountains send water flooding through an intricate series of shallow lagoons and marshes. Many of these areas dry out during the summer months. This image was acquired in the fall, when the area was relatively dry.

- The Shadegan wetlands support an array of living things. Sheep, cattle, and water buffalo roam the area, while Mesopotamian himri, carp, and catfish are commonly caught in the pond's waters. Dozens of bird species—including several types of ducks, terns, gulls, and egrets—can be found in Shadegan Wildlife Refuge.

- The refuge is one of the most important sites in the world for the marbled teal, a diving duck. Shadegan supports about 10,000 to 20,000 of these birds in the winter, about half of the world's population.

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Figure 94: Image of the Shadegan Pond in Iran, acquired on September 3, 2012 with the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) of JAXA on the NASA's Terra satellite (image credit: NASA Earth Observatory image by Jesse Allen, caption by Adam Voiland)

• January 11, 2017: In January 2007, satellites captured an extraordinary example of hole-punch clouds visible over the southern United States. But occurrences of the cloud type, albeit usually less pronounced, show up every year over Earth's mid- and high-latitudes. A more recent display developed over eastern China, visible in the image of Figure 95, acquired on December 28, 2016, with MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite. 75)

- This strange phenomenon results from a combination of cold temperatures, air traffic, and atmospheric instability. If you were to look from below, it would appear as if part of the cloud was falling out of the sky. As it turns out, that's actually what's happening.

- The mid-level clouds are initially composed of liquid drops at a super-cooled temperature below 0° Celsius. As an airplane passes through the cloud, it creates a disturbance that triggers freezing. Ice particles then quickly grow in the place of the water droplets. Eventually the ice crystals in these patches of clouds grow large enough that they literally fall out of the sky—earning hole-punch clouds their alternate name: "fallstreak holes." Falling crystals are often visible in the center of the voids.

- The formations in this image are less like holes and more linear, like long canals. The same basic processes are responsible for producing both configurations. Whether the void takes on a circular or linear shape depends on differences such as cloud thickness, wind shear, and air temperature. Hole-punch and canal clouds can appear together, as they did in this image from December 2015. They often occur in the vicinity of an airports.

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Figure 95: The MODIS instrument on Terra acquired this image on Dec. 28, 2016 over eastern China showing the display of canal clouds (image credit: NASA Earth Observatory, image by Joshua Stevens,caption by Kathryn Hansen)

• On November 24, 2016, Tokyo received its first November snowfall in more than half a century. The MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite captured this natural-color image the same day. The snow fell in and around the Japanese capital, coating the metropolitan area and accumulating along some sidewalks (Figure 96). 76)

- Figure 97, a false-color image from MODIS on Terra, shows a stark contrast between snow (blue) and clouds (white). The snow traces the contours of surrounding mountains and is distinguishable from clouds offshore. Central Tokyo is gray-brown in color, suggesting less accumulation or faster melting. Urban centers tend to shed snow faster than surrounding countryside because they are often hotter, a result of the urban heat island effect.

- The November dusting was caused by a cold air mass moving down from the Arctic, according to the Japan Meteorological Agency. Meteorologists connected the storm to the Arctic oscillation, a climate pattern that affects the northern hemisphere. Usually, high air pressure in the mid-latitudes prevents colder, low-pressure air seeping down from the Arctic. However, weaker pressure systems occasionally disrupt this barrier, and colder air can penetrate further south, as in this case.

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Figure 96: Snow-covered Tokyo region as acquired by the MODIS instrument on November 25, 2016 (image credit: NASA Earth Observatory, image by Joshua Stevens)

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Figure 97: False-color image of Tokyo, acquired on Nov. 25, 2016, showing the stark contrast between snow (blue) and clouds (white), image credit: NASA Earth Observatory, image by Joshua Stevens

• Sept. 8, 2016: In August 2016, the return of sunlight on the Antarctic Peninsula meant that the landscape became visible again in natural-color satellite imagery. That's when scientists saw something interesting: a rift along Larsen C—the continent's fourth-largest ice shelf—has grown considerably longer. 77)

- The scenario is similar to what occurred before a calving event and partial collapse of Larsen B in 2002. But exactly what's in store for Larsen C remains to be seen. "We don't know yet what will happen here," said Ala Khazendar of NASA's Jet Propulsion Laboratory.

- Figure 98 was acquired with MISR's downward-looking (nadir) camera. This natural-color image has a red tint due to the steep lighting angle, as the Sun does not reach far above the horizon in August. The ice shelf comprises the left half of the image, and thinner sea ice appears on the right.

- Figure 99 shows the same area. By combining these different angles in one image, one can discern surface roughness. Rougher surfaces appear pink and smoother areas appear purple. The ice shelf is generally smoother than the sea ice, with the exception of the crack—an indication that it is actively growing, according to the MISR team. Project MIDAS, a group in the United Kingdom that has been tracking the rift, reported that the crack grew 22 km over the past six months. It now stretches 130 km.

- Both images show other fissures as well, all of which terminate at about the same distance south of the lengthening crack. "People have been intrigued by this," Khazendar said. "It's quite a remarkable feature, how they open and then seem to stop opening." There are a few hypotheses as to why that happens. The cracks might come to a stop when they reach a suture zone—an area where sectors of ice feeding the shelf are advancing at different speeds, creating shear where they flow together. Ice in this zone is already so fractured that it halts further propagation of the big, crosswise cracks.

- The cracks also could have reached an area where marine ice has formed on the bottom of the ice shelf. Marine ice is relatively warm and less stiff, so it can accommodate higher levels of strain without fracturing. The crack that's actively lengthening, however, has overcome those obstacles. "What's happening now is different," Khazendar said. "This crack goes farther and has started propagating northwards."

- Even before signs of the lengthening appeared at the surface, Khazendar and colleagues suspected something was going on. A study in 2011 that measured ice velocity showed a "line" across the shelf; everything between that line and front of ice shelf was flowing noticeably faster than everything upstream. They proposed that the line traced the location of a crevasse growing upward along the bottom of the ice sheet. Then in 2014, the MIDAS team first detected the rift growing at the surface.

- "What might be happening is that there is enhanced melting at bottom of ice shelf, resulting in the removal of the softer marine ice, allowing fractures to be filled with ocean water," Khazendar said. "When that happens, it could cause pre-existing bottom crevasses to propagate up through the ice shelf."

- Cracks and calving of ice from the front of an ice shelf is a normal process. Shelves are fed by ice coming from glaciers and ice streams from the interior of the continent. They advance into the ocean until a calving event takes place. The shelf front retreats and then advances again. The whole cycle can occur over the span of a few decades. "That's just part of life for an ice shelf," Khazendar said. "That's how they behave."

- In the case of Larsen B, the big calving events took place with a frequency that did not allow enough time for the shelf to re-advance. As a result, the front of the shelf kept retreating in a run up to the big disintegration event that occurred in just six weeks in 2002. "The growing crack on Larsen C could be the beginning of a process that will end up like Larsen B," Khazendar said. "If a big calving event takes place, we will be interested to see how the shelf itself reacts. But all the indications so far are that it is relatively stable, albeit with intimations of change."

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Figure 98: The rift is visible in this image acquired on August 22, 2016, with the MISR (Multi-angle Imaging SpectroRadiometer) instrument on Terra (image credit: NASA Earth Observatory images by Jesse Allen and the MISR Team)

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Figure 99: Composite image of the same area from MISR's backward-, vertical-, and forward-pointing cameras (image credit: NASA Earth Observatory images by Jesse Allen and the MISR Team)

• July 12, 2016: NASA's Terra satellite observed a large dust storm off the coast of Chile. It is unusual to see such large dust events emerge from the west coast of South America, according to atmospheric scientists. Winds there "are not conducive to developing major dust storms like those that we see in North Africa or in Asia," said Joseph Prospero, an atmospheric scientist at the University of Miami. 78)

- The local topography hinders the formation of dust storms, as the Andes Mountains run along South America's western flank and block winds arising in the east. The mountain range stretches more than 7,000 km from north to south, and stands more than 500 km wide in some areas. Usually, dust storms during this time of year (southern, or austral, winter) will blow eastward toward the Atlantic Ocean, said Santiago Gasso, an aerosol scientist at NASA's Goddard Space Flight Center.

- Globally, natural sources account for roughly 75 percent of dust emissions, while anthropogenic (manmade) sources account for roughly 25 percent, according to research published in Reviews of Geophysics. On July 8, the source was natural. The image of Figure 100 suggests that the dust source is located between the Andes and the Pacific coast. The slice of land there is narrow, with steeply rising walls. The dust source could be on an elevated slope, making it easier for dust to lift and travel far. It also could be driven by low-level winds—possibly katabatic winds, which blow downslope off the continent. The term katabatic comes from the Greek "katabaino," meaning "to descend." Such winds develop as air that comes in contact with cold, high-altitude ground cools by radiation. The air increases in density, and flows downhill. It can pick up speed, causing gale-force winds.

- The stormy conditions that lofted the dust on July 8 also brought wind, rain, and snow leading to the closure of at least two airports, Chile's Teletrece news site reported.

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Figure 100: On July 8, 2016, the MODIS instrument on Terra acquired this natural-color image of an airborne dust cloud off the coast of Chile (image credit: NASA Earth Observatory, Jeff Schmalz)

• May 18, 2016: April in Greenland is typically very cold, though some years buck the trend. In 2012, for example, the surface of the ice sheet started melting early and then experienced the most extensive melting since the start of the satellite record in 1978. Weather events and temperature anomalies this April suggest that 2016 may be off to a similar start.

- The temperature anomaly map of Figure 101 is based on data from MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA's Terra satellite. Observed by satellites uniformly around the world, LSTs (Land Surface Temperatures) are not the same as air temperatures. Instead, they reflect the heating of the surface by sunlight, and they can sometimes be significantly hotter or cooler than air temperatures.

- "The most remarkable aspect here is the incredible departure from 2001-2010 average, especially deep in the ice sheet interior," said Santiago de la Peña, a research scientist at Ohio State University. "This is accentuated by the fact that the northern regions of the United States and Canada actually experienced cooler than usual temperatures." According to de la Peña, a high-pressure weather system sat over the ice sheet through most of April. The system caused temperatures across Greenland to spike, reaching or matching record temperatures in many places. "There have been occasional warming events in the past during spring over Greenland," he noted, "but they affected only local areas and were not as intense."

- Still, warming events in Greenland are not entirely without precedent. Research by Dorothy Hall, an emeritus scientist at NASA's Goddard Space Flight Center, has shown that major melt events like those in 2012 and 2002 are not uncommon.

- De la Peña thinks such events will become more common in the future as atmospheric warming in the Arctic brings about longer melt seasons. For now, he notes that it is still early to predict how the melt season in 2016 will unfold. "High temperatures are still being recorded in May, suggesting we will have major melt events during the summer."

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Figure 101: The MODIS map of Terra shows land surface temperatures for April 2016 compared to the 2001–2010 average for the same month. Red areas were hotter than the long-term average; some areas were as much as 20º Celsius warmer. Blue areas were below average, and white pixels had normal temperatures. Gray pixels were areas without enough data, most likely due to excessive cloud cover (image credit: NASA Earth Observatory, image by Jesse Allen)

• May 7, 2016: In early May 2016, a destructive wildfire burned through Canada's Fort McMurray in the Northern Alberta region. Windy, dry, and unseasonably hot conditions all set the stage for the fire. Winds gusted over 32 km/hour, fanning the flames in an area where rainfall totals have been well below normal in 2016. Ground-based measurements showed that the temperature soared to 32º Celsius on May 3 as the fire spread. 79)

- Observed by satellites uniformly around the world, LSTs (Land Surface Temperatures) are not the same as air temperatures. Instead, they reflect the heating of the land surface by sunlight, and they can sometimes be significantly hotter or cooler than air temperatures (Figure 102). The intense heat coincided with a weather pattern called an omega block. A large area of high pressure stalled the usual progression of storms from west to east. In Alberta, that left sinking, hot air parked over the region while the block was in place. But even before the omega block emerged, seasonal data show that winter in Alberta was warmer than usual.

- According to Robert Field, a Columbia University scientist based at NASA's Goddard Institute for Space Studies, El Niño likely played a role in the warmth. The Virginia Hills fire in central Alberta (May 1998) burned under a similar El Niño phase. "That fire occurred under comparable fire danger conditions, part of which you can trace to El Niño," Field said.

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Figure 102: The temperature anomaly map is based on data from the MODIS instrument on the Terra satellite. The map shows the LST (Land Surface Temperature) from April 26 to May 3, 2016, compared to the 2000–2010 average for the same one-week period. Red areas were hotter than the long-term average; blue areas were below average. White pixels had normal temperatures, and gray pixels did not have enough data, most likely due to cloud cover (image credit: NASA Earth Observatory, image by Jesse Allen)

- The image of Figure 103 shows Fort McMurray on May 4, 2016, acquired by the Enhanced Thematic Mapper Plus (ETM+) on the Landsat-7 satellite. This false-color image combines shortwave infrared, near infrared, and green light (bands 5-4-2). Near- and short-wave infrared help penetrate clouds and smoke to reveal the hot spots associated with active fires, which appear red. Smoke appears white and burned areas appear brown. On this day the fire spanned about 100 km2; by the morning of May 5, it spanned about 850 km2 (Ref. 79).

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Figure 103: ETM+ image of Landsat-7 of the Fort McMurray fire, acquired on May 4, 2016. Also visible in the Landsat image is the fire's complex pattern, with many active fronts (image credit: NASA Earth Observatory, image by Jesse Allen)

• May 4, 2016: April in Southeast Asia is usually a hot month, following the cool, dry season and preceding the monsoon season. But April 2016 was not your typical April. Throughout the month, ground-based measurements of air temperatures soared above average; one location in Thailand even broke the national record. 80)

- Satellite observations show a similarly hot picture. The map of Figure 104 shows land surface temperatures from April 2016 compared to the 2000–2012 average for the same month. Red areas were hotter than the long-term average by as much as 12º Celsius in some places; blue areas were below average. White pixels had normal temperatures, and gray pixels did not have enough data, most likely due to excessive cloud cover.

- According to news reports, at least 50 towns and cities matched or broke their daily air temperature records. On April 28, the temperature in Mae Hong Son was the highest ever recorded in Thailand, reaching 44.6 º Celsius.

- Southeast Asia was not the only area that endured intense heat in April. In India, ground-based measurements recorded temperatures 4-5º Celsius above normal. At least 300 people are reported to have died from heat-related complications during the month. A year earlier, more than 2,500 people died during India's 2015 heat wave—one of the five deadliest on record.

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Figure 104: This temperature anomaly map is based on data from the MODIS instrument on NASA's Terra satellite, acquired in April 2016 (image credit: NASA Earth Observatory, image by Jesse Allen)

Legend to Figure 104: Observed by satellites uniformly around the world, land surface temperatures (LSTs) are not the same as air temperatures. Instead, they reflect the heating of the land surface by sunlight, and they can sometimes be significantly hotter or cooler than air temperatures.

• April 18, 2016: Long-term cloud cover study of MODIS data on Terra and on Aqua reveals species habitat. Much of Earth's biodiversity is concentrated in areas where not enough is known about species habitats and their wider distributions, making management and conservation a challenge. To address the problem, scientists at the University at Buffalo and Yale University used NASA satellite data to study cloud cover, which they found can help identify the size and location of important animal and plant habitats. 81) 82)

- Clouds influence such environmental factors as rain, sunlight, surface temperature and leaf wetness-all of which dictate where plants and animals can survive. As part of their study, researchers examined 15 years of data from NASA's Earth-orbiting Terra and Aqua satellites and built a database containing two images per day of cloud cover for nearly every square kilometer of the planet from 2000 to 2014. The study found that variations in cloud cover sharply delineated the boundaries of ecological biomes relevant to many unique species. 83)

- Advanced spatial assessment and monitoring of biodiversity in today's rapidly changing world is vital for managing future biological resources and a key element of several 2020 targets of the Convention on Biological Diversity and the Intergovernmental Platform on Biodiversity and Ecosystem Services. Growing evidence highlights the importance of fine-grain (≤1 km) climatic and environmental variability in driving the spatial distribution and abundance of organisms and the need to correctly capture this variation globally. Ecological research at regional to global extents remains reliant on environmental information that lacks important detail and is often interpolated between ground stations over vast distances of highly variable terrain.

- Cloud cover influences processes ranging from reproductive success in reptiles to leaf wetness, CO2 uptake, and the geographic distribution of plants. Especially in the tropics, seasonal variability of cloud cover is typically more important than day length and solar angle in reducing available solar irradiance, with multi-fold ecological consequences. These effects are difficult to observe in other remotely sensed products including vegetation indices, which for many parts of the world do not show much change throughout the year.

- The new 1 km dataset confirms equatorial South America, the Congo River basin in Africa, and Southeast Asia as the cloudiest regions of the world, with annual cloud frequencies (proportion of days with a positive cloud flag) ≥80% (Figure 105A). But, in contrast to existing evidence (S1 Table), the new product captures the frequency of cloud cover at substantially increased spatial resolution. In many regions (often but not always mountainous), cloud cover varies starkly over very short distances (Figure 105C), revealing variability hidden in spatially aggregated cloud products currently used in ecosystem, biodiversity, and climate modeling that are >100–10,000 times coarser.

- Remotely sensed information has the potential to revolutionize our understanding of spatial ecoclimatological patterns and processes through direct capture of environmental variation at fine spatial grain and global extent. Here, we have shown how global cloud dynamics can be quantified in unprecedented spatial detail and that cloud-associated factors are significantly associated with the distribution of various aspects of biodiversity habitats over large spatial scales.

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Figure 105: Global 1 km cloud metrics. A) Mean annual cloud frequency (%) over 2000–2014. B) Inter-annual variability in cloud frequency (mean of 12 monthly standard deviations). C) Spatial variability (standard deviation of mean annual cloud frequency within a one-degree, ~110 km, circular moving window). D) Intra-annual variability in cloud frequency (standard deviation of 12 monthly mean cloud frequencies). Grey indicates the (A) median global cloud frequency (51%) and (B,D) median inter-annual variability (11%), blues indicate areas with below-median values, and reds indicate areas with higher-than-median values. Data are available only for MODIS land tiles, resulting in missing data in black tiles over oceans (image credit: A. M. Wilson, W. Jetz)

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Figure 106: Seasonal cloud concentration. A) Color key illustrating the distribution of global cloud seasonality and concentration. The hue indicates the month of peak cloudiness, while the saturation and value indicate the magnitude of the concentration ranging from 0 (black, all months are equally cloudy) to 100 (all clouds are observed in a single month). B) Global distribution of seasonal cloud concentration with two red boxes indicating the locations of panels C and D. Coastlines shown in white, areas with no data are dark grey. C) Regional plot of northern South America illustrating the transition from June–July–August to December–January–February cloudiness with little seasonality (dark colors) at high elevations. D) Regional plot of southern Africa illustrating the transition from the Mediterranean climate in the southwest to the summer rainfall region in the northeast. Note the incursions of summer clouds and associated rainfall (red colors) along the southern coast. In C) and D), red lines indicate ecoregion boundaries (image credit: A. M. Wilson, W. Jetz)

• April 13, 2016: Antarctica has shed two new, large icebergs into the Southern Ocean. The bergs are the result of a crack that had been spreading across the Nansen Ice Shelf. The progression of the crack was visible in a pair of satellite images acquired in December 2013 and 2015. Ryan Walker and Christine Dow, glaciologists at NASA/GSFC (Goddard Space Flight Center), flew along the crack in late 2015. It was clearly still attached. On April 6, 2016, with southern winter soon to set in, satellite imagery indicated that the cracking ice front was still holding on. 84)

- The Nansen Ice Shelf previously measured about 35 km across and 50 km long. For comparison, the Drygalski Ice Tongue just south of Nansen stretches 80 km into the sea. Of the two bergs shed from Nansen, only one is large enough to meet the size criteria for naming and tracking by the U.S. National Ice Center. This larger piece is named C33.

- But why did the crack finally give out? According to Walker, summer melting probably helped weaken and break up the shelf fragments and sea ice (the mélange) within the crack, which acted like glue to keep the bergs attached. Summer melt also could have helped the deeply fissured ice to break further, completing the crack across the shelf.

- Once broken off, the new icebergs would have been blown away from the shelf by the strong katabatic winds that blow out to sea. "Nansen usually has pretty strong katabatic winds," Walker said.

- Walker emphasized that this is routine iceberg calving—there are indications that similar events occurred there in the 1960s—and not a collapse of the ice shelf. Still, some scientists are concerned for a different reason; the icebergs are threatening scientific equipment in the area. Scientists at New Zealand's National Institute of Water and Atmospheric Research (NIWA) say the bergs are deep enough that they cold snag a mooring deployed in Terra Nova Bay. The mooring collects data on the effects of climate change on sea ice and ice shelves.

- "We won't know until we go back next summer whether it is still there. We could lose a whole year of data. If that happens it will leave a gap in our research and that's unfortunate," said oceanographer Mike Williams in a NIWA press release. "However, it is a risk we have to take. We could see the crack from satellite images but predicting when an ice shelf will calve is difficult. It could have happened any time in the next five years."

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Figure 107: On April 7, 2016, in the last days before winter darkness, MODIS on Terra acquired this image as the bergs broke away. (image credit: NASA Earth Observatory,, image by Jesse Allen)

As of April 1, 2016, all Earth imagery from the Japanese ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) instrument aboard NASA's Terra spacecraft since late 1999, is now available to users everywhere at no cost. The public will have unlimited access to the complete 16-plus-year database for Japan's ASTER instrument of METI (Ministry of Economy, Trade and Industry), which images Earth to map and monitor the changing surface of our planet. ASTER's database currently consists of more than 2.95 million individual scenes. The content ranges from massive scars across the Oklahoma landscape from an EF-5 tornado and the devastating aftermath of flooding in Pakistan, to volcanic eruptions in Iceland and wildfires in California. 85)

- Previously, users could access ASTER's global digital topographic maps of Earth online at no cost, but paid METI a nominal fee to order other ASTER data products. In announcing the change in policy, METI and NASA cited ASTER's longevity and continued strong environmental monitoring capabilities. Launched in 1999, ASTER has far exceeded its five-year design life and will continue to operate for the foreseeable future as part of the suite of five Earth-observing instruments on Terra.

- The broad spectral coverage and high spectral resolution of ASTER provide scientists in numerous disciplines with critical information for surface mapping and monitoring of dynamic conditions and changes over time. Example applications include monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud morphology and physical properties, evaluating wetlands, monitoring thermal pollution, monitoring coral reef degradation, mapping surface temperatures of soils and geology, and measuring surface heat balance.

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Figure 108: In Dec. 2015, one of Nicaragua's largest volcanoes, Momotombo, erupted for the first time since 1905. Continued activity at the end of February and into March 2016 produced large ash columns and pyroclastic (superheated ash-and-block) flows. On March 2, 2016, ASTER captured the volcano's eruptive activity during the day with its visible bands, and the previous night with its thermal infrared bands. The composite image shows a large blue-gray ash cloud covering the volcano's summit. The superimposed night data show the hot flows (in yellow) on the northeast flank, and the active summit crater in white. The data cover an area of 17 km x 18 km, located at 12.7º north, 86.6º west. 86)

Legend to Figure 108: With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of 15 to 90 m, ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched Dec. 18, 1999, on Terra. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and data products.

• In March 2016, the Southern United States received a remarkable amount of precipitation. In the days after the slow-moving weather system cleared out, flood waters rose across several major river basins. 87)