Minimize Suomi NPP

Suomi NPP (National Polar-orbiting Partnership) Mission

Spacecraft     Launch    Mission Status     Sensor Complement    Ground Segment    References

In January 2012, NASA has renamed its newest Earth-observing satellite, namely NPP (NPOESS Preparatory Project) launched on October 28, 2011, to Suomi NPP (National Polar-orbiting Partnership). This is in honor of the late Verner E. Suomi, a meteorologist at the University of Wisconsin, who is recognized widely as "the father of satellite meteorology." The announcement was made on January 24, 2012 at the annual meeting of the American Meteorological Society in New Orleans, Louisiana.

Verner Suomi (1915-1995) was born and raised in Minnesota. He spent nearly his entire career at the University of Wisconsin-Madison, where in 1965 he founded the university's Space Science and Engineering Center (SSEC) with funding from NASA. The center is known for Earth-observing satellite research and development. In 1964, Suomi served as chief scientist of the U.S. Weather Bureau for one year. Suomi's research and inventions have radically improved weather forecasting and our understanding of global weather.

Table 1: Some background on the renaming of the NPP mission 1) 2)

NPP is a joint NASA/IPO (Integrated Program Office)/NOAA LEO weather satellite mission initiated in 1998. The primary mission objectives are:

1) To demonstrate the performance of four advanced sensors (risk reduction mission for key parts of the NPOESS mission) and their associated Environmental Data Records (EDR), such as sea surface temperature retrieval.

2) To provide data continuity for key data series observations initiated by NASA's EOS series missions (Terra, Aqua and Aura) - and prior to the launch of the first NPOESS series spacecraft. Because of this second role, NPP is sometimes referred to as the EOS-NPOESS bridging mission.

Three of the mission instruments on NPP are VIIRS (Visible/Infrared Imager and Radiometer Suite), CrIS (Cross-Track Infrared Sounder), and OMPS (Ozone Mapping and Profiler Suite). These are under development by the IPO. NASA/GSFC developed a fourth sensor, namely ATMS (Advanced Technology Microwave Sounder). This suite of sensors is able to provide cloud, land and ocean imagery, covering the spectral range from the visible to the thermal infrared, as well as temperature and humidity profiles of the atmosphere, including ozone distributions. In addition, NASA is developing the NPP S/C and providing the launch vehicle (Delta-2 class). IPO is providing satellite operations and data processing for the operational community; NASA is supplying additional ground processing to support the needs of the Earth science community. 3) 4) 5) 6) 7) 8)

CERES instrument selected for NPP and NPOESS-C1 missions: 9)

In early 2008, the tri-agency (DOC, DoD, and NASA) decision gave the approval to add the CERES (Clouds and the Earth's Radiant Energy System) instrument of NASA/LaRC to the NPP payload. The overall objective of CERES is to provide continuity of the top-of-the-atmosphere radiant energy measurements - involving in particular the role of clouds in Earth's energy budget. Clouds play a significant, but still not completely understood, role in the Earth's radiation budget. Low, thick clouds can reflect the sun's energy back into space before solar radiation reaches the surface, while high clouds trap the radiation emitted by the Earth from escaping into space. The total effect of high and low clouds determines the amount of greenhouse warming. - CERES products include both solar-reflected and Earth-emitted radiation from the top of the atmosphere to the Earth's surface.

In addition, the tri-agency decision called also for adding two instruments, namely CERES and TSIS (Total Solar Irradiance Sensor), to the payload of the NPOESS-C1 mission.

Background: The CERES instrument is of ERBE (Earth Radiation Budget Experiment) heritage of NASA/LaRC, first flown on the ERBS (Earth Radiation Budget Satellite) mission, launch Oct. 5, 1984, then on NOAA-9 (launch Dec. 12, 1984), and NOAA-10 (launch Sept. 17, 1986). The CERES instrument is flown on TRMM (Tropical Rainfall Measuring Mission), launch Nov. 27, 1997, as a single cross-track radiance sensor of short (0.3-5 μm), long- (8-12 μm) and total wave (0.3-100 μm; prototype flight model flown on TRMM). Two further advanced CERES instrument assemblies are also being flown on NASA's Terra mission (launch Dec. 18, 1999) as a dual-track scanner (two radiometers) in XT (Cross-Track ) support or in a RAPS (Rotational Azimuth Plane Scan) support mode. Another CERES instrument system (two radiometers) are being flown on Aqua of NASA (launch May 4, 2002).

The CERES instrument on NPP will provide continuity the long climate data record of the Earth's radiant energy.


In Feb. 2010, the NPOESS (National Polar-orbiting Environmental Satellite System) tri-agency program was terminated by the US government due to severe cost overruns and program delays. In 2009, an IRT (Independent Review Team) concluded that the current NPOESS program, in the absence of managerial and funding adjustments, has a low probability of success and data continuity is at extreme risk. The Office of Science and Technology, with the Office of Management and Budget and the National Security Council, as well as representatives from each agency, examined various options to increase the probability of success and reduce the risk to data continuity.

NOAA's restructured satellite program, the civilian JPSS (Joint Polar Satellite System), was created in the aftermath of the White House's Feb. 2010 decision to cancel NPOESS. The development of the new JPSS will be managed by NASA/GSFC while the spacecraft will be owned and operated by NOAA. The launch of JPSS-1 is planned for 2017.

NOAA, through NASA as its acquisition agent, will procure the afternoon orbit assets that support its civil weather and climate requirements and DoD will independently procure assets for the morning orbit military mission - referred to as DWSS (Defense Weather Satellite System). Both agencies will continue to share environmental measurements made by the system and support the operations of a shared common ground system.

The Administration decision for the restructured Joint Polar Satellite System will continue the development of critical Earth observing instruments required for improving weather forecasts, climate monitoring, and warning lead times of severe storms. NASA’s role in the restructured program will be modeled after the procurement structure of the successful POES (Polar Operational Environmental Satellite) and GOES (Geostationary Operational Environmental Satellite) programs, where NASA and NOAA have a long and effective partnership. The partner agencies are committed to maintaining collaborations towards the goal of continuity of earth observations from space.

The restructured Joint Polar Satellite System is planned to provide launch readiness capability in FY 2015 and FY 2018 (with launches of JPSS-1 in 2016 and JPSS-2 in 2019, respectively) in order to minimize any potential loss of continuity of data for the afternoon orbit in the event of an on orbit or launch failure of other components in the system. Final readiness dates will not be baselined until all transition activities are completed.

The NPP project, as preparatory mission for the NPOESS program, received its OK to continue in the early spring of 2010. However, the close partnership with NPOESS can still be seen in all the references throughout the documentation of this file.

NPP serves as a bridge mission between NASA's EOS (Earth Observing System) series of satellites and the next-generation JPSS (Joint Polar Satellite System), a NOAA program that will also collect weather and climate data.

NPP will provide on-orbit testing and validation of sensors, algorithms, ground-based operations, and data processing systems that will be used in the operational JPSS mission. By 2016, the first JPSS spacecraft will be launched into the afternoon orbit to provide significantly improved operational capabilities and benefits to satisfy critical civil and national security requirements for spaceborne, remotely sensed environmental data. The last satellite in the JPSS mission constellation is expected to continue operations until about 2037.

Table 2: JPSS (Joint Polar Satellite System) - NPOESS program terminated 10)

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Figure 1: Overview of Suomi NPP mission segments and architecture (image credit: NASA) 11)

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Figure 2: NOAA POES continuity of weather observations (image credit: NOAA)




Spacecraft:

The Suomi NPP spacecraft has been built and integrated by BATC (Ball Aerospace and Technologies Corporation) of Boulder, CO (NASA/GSFC contract award in May 2002). The platform design is a variation of BATC's BCP 2000 (Ball Commercial Platform) bus of ICESat and CloudSat heritage. The spacecraft consists of an aluminum honeycomb structure. 12) 13) 14)

The ADCS (Attitude Determination and Control Subsystem) provides 3-axis stabilization using 4 reaction wheels for fine attitude control, 3 torquer bars for momentum unloading, thrusters for coarse attitude control (such as during large-angle slews for orbital maintenance), 2 star trackers for fine attitude determination, 3 gyros for attitude and attitude rate determination between star tracker updates, 2 Earth sensors for safe-mode attitude control, and coarse sun sensors for initial attitude acquisition, all monitored and controlled by the spacecraft controls computer. ADCS provides real-time attitude knowledge of 10 arcsec (1 sigma) at the S/C navigation reference base, real-time spacecraft position knowledge of 25 m (1 sigma), and attitude control of 36 arcsec (1 sigma).

The EPS (Electrical Power Subsystem) uses GaAs solar cells to generate an average power of about 2 kW (EOL). The solar array rotates once per orbit to maintain a nominally normal orientation to the sun). In addition, a single-wing solar array is mounted on the anti-solar side of the S/C; its function is to preclude thermal input into the sensitive cryo radiators of the VIIRS and CrIS instruments. A regulated 28 ±6 VDC power bus distributes energy to all S/C subsystems and instruments. A NiH (Nickel Hydrogen) battery system provides power for eclipse phase operations.

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Figure 3: Artist's rendition of the deployed Suomi NPP spacecraft (image credit: BATC)

The C&DHS (Command & Data Handling Subsystem) collects instrument data (12 Mbit/s max total) via an IEEE 1394a-2000 “FireWire” interface (VIIRS, CrIS and OMPS instruments), and stores the data on board. Communications with ATMS occurs across the MIL-STD-1553 data bus. A new 1394/FireWire chipset was developed for the communication support, bringing spaceborne communications (onboard data handling and RF data transmission) onto a new level of service range and performance.

Upon ground command or autonomously, the C&DHS transmits stored instrument data to the communication system for transmission to the ground. Also, the C&DHS generates a real-time 15 Mbit/s data stream consisting of instrument science and telemetry data for direct broadcast via X-band to in-situ ground stations.

Parameter

Value

Parameter

Value

S/C dimensions

1.3 m x 1.3 m x 4.2 m

S/C total mass

~2200 kg

Instrument data rate

12.5 Mbit/s

Payload mass

464 kg

Downlink data rate

300 Mbit/s in X-band
128 kbit/s in S-band

Position knowledge
Attitude knowledge
Attitude control

75 m each axis
< 21 arcsec each axis
<108 arcsec each axis

Table 3: Some NPP spacecraft characteristics

The spacecraft is designed to be highly autonomous. For satellite safety, the S/C controls computer monitors spacecraft subsystem and instrument health. It can take action to protect itself (for example, in the event of an anomaly that threatens the thermal or optical safety and health of the S/C, then it can enter into a safe or survival mode and stay in the mode indefinitely until ground analysis and resolution of the anomaly). In addition, the satellite is designed to require infrequent uploads of commands (the instruments operate mainly in a mapping mode and therefore require few commands even for periodic calibration activities, and a sufficiently large command buffer is available for storage of approximately 16 days of commands).

The spacecraft has an on-orbit design lifetime of 5 years (available consumables for 7 years). The S/C dry mass is about 1400 kg. NPP is designed to support controlled reentry at the end of its mission life (via propulsive maneuvers to lower the orbit perigee to approximately 50 km and target any surviving debris for open ocean entry). NPP is expected to have sufficient debris that survives reentry so as to require controlled reentry to place the debris in a pre-determined location in the ocean.

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Figure 4: Photo of the nadir deck of the NPP spacecraft (image credit: BATC, IPO)

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Figure 5: Suomi NPP spacecraft on-orbit configuration (image credit: NASA)


Launch: The NPP spacecraft was launched on October 28, 2011 on a Delta-2-7920-10 vehicle from VAFB, CA (launch provider: ULA). The launch delay of nearly a year was due to development/testing problems of the CrIS (Cross-track Infrared Sounder) instrument. 15) 16) 17)

Orbit: Sun-synchronous near-circular polar orbit (of the primary NPP), altitude = 824 km, inclination =98.74º, period = 101 minutes, LTDN (Local Time on Descending Node) at 10:30 hours. The repeat cycle is 16 days (quasi 8-day).

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Figure 6: Photo of the NPP launch (image credit: NASA)

Secondary payloads: The secondary payloads on the Suomi NPP mission are part of NASA's ElaNa-3 (Educational Launch of Nanosatellites) initiative. All secondary payloads will be deployed from standard P-PODs (Poly Picosatellite Orbital Deployer). 18)

• AubieSat-1, a 1 U CubeSat of AUSSP (Auburn University Student Space Program), Auburn, AL, USA.

• DICE (Dynamic Ionosphere CubeSat Experiment), two nanosatellites (1.5U CubeSats) of the DICE consortium (Utah State University, Logan, UT, USA) with a total mass of 4 kg.

• E1P-2 (Explorer-1 PRIME-2) flight unit-2, a CubeSat mission of MSU (Montana State University), Bozeman, MT, USA.

• RAX-2 (Radio Aurora eXplorer-2), an NSF-sponsored 3U CubeSat of the University of Michigan, Ann Arbor, MI, USA

• M-Cubed (Michigan Multipurpose Minisat), a 1U CubeSat of the University of Michigan, Ann Arbor, MI. M-Cubed features also the collaborative JPL payload called COVE (CubeSat On-board processing Validation Experiment).

Orbit of the secondary payloads: After the deployment of the NPP primary mission, the launch vehicle transfers all secondary payloads into an elliptical orbit for subsequent deployment. This is to meet the CubeSat standard of a 25 year de-orbit lifetime as well as the science requirements of the payloads riding on this rocket. The rocket will take care of the maneuvering and when it reaches the correct orbit, it will deploy all of the secondary payloads, into an orbit of ~ 830 km x ~ 350 km, inclination = 99º.


RF communications:

The NPP satellite collects instrument data, stores the data onto a solid-state recorder of about 280 Gbit capacity. A two-axis gimbaled X-band antenna is mounted on a post above the payload to provide a high bandwidth downlink. Source science data are generated at a rate of about 12.5 Mbit/s. Global, or stored mission data will be downlinked at X-band frequencies (8212.5 MHz, data rate of 300 Mbit/s) to a 13 m ground receiving station located at Svalbard, Norway.

Two wideband transmissions carry NPP mission data: SMD (Stored Mission Data) and HRD (High-Rate Data). These transmissions are distinct from the narrowband data streams containing the satellite's housekeeping telemetry. Mission data are collected from each of the five instruments (ATMS, VIIRS, CrIS, OMPS, CERES).

These data, along with spacecraft housekeeping data, are merged and provided to the ground on a real-time 15 Mbit/s downlink, called HRD direct broadcast. Instrument and housekeeping data are also provided to the SSR (Solid State Recorder) for onboard storage and playback as SMD. The SMD are stored in the spacecraft's SSR and downlinked at 300 Mbit/ss through playback of the SSR once per orbit over the NPP/NPOESS SvalSat ground station in Svalbard, Norway.

The HRD stream is similar to the SMD as it consists of instrument science, calibration and engineering data, but it does not contain data from instrument diagnostic activities. The HRD is constantly transmitted in real time by the spacecraft to distributed direct broadcast users. Output to the HRD transmitter is at a constant 15 Mbit/s rate.

Data acquisition: In early 2004, IPO in cooperation with NSC (Norwegian Space Center), installed a 13 m antenna dish - a dual X/S-band configuration, at SGS (Svalbard Ground Station), located at 78.216º N, 20º E on the Norwegian Svalbard archipelago (also referred to as Spitzbergen) near the town of Longyearbyen. The SGS complex is owned by the Norwegian Space Center (Norsk Romsenter), Oslo, Norway, and operated by the Tromsø Satellite Station (TSS) through its contractor KSAT (Kongsberg Satellite Services). SGS is the primary data downlink site for global stored mission data (SMD) from NPP. Svalbard is located at a high enough latitude to be able to “see” (i.e., track) all 14 daily NPP satellite passes. 19)

The global NPP data will be transmitted from Svalbard within minutes to the USA via a fiber-optic cable system that was completed in January 2004 as a joint venture between the IPO, NASA, and NSC. Once the data stream is in the USA, the RDRs (Raw Data Records) will be processed into SDRs (Sensor Data Records) and EDRs by the Interface Data Processing Segment (IDPS). The performance goal calls for EDR delivery within 3 hours of acquisition. - NPP also focuses on ground segment risk reduction by providing and testing a subset of an NPOESS-like ground segment. Developed algorithms can be thoroughly tested and evaluated. This applies also to the methods of instrument verification, calibration, and validation.

Note: The new antenna and fiber-optic link at SGS are already being used to acquire data of five to ten Coriolis/WindSat passes/day and delivery of the data to users in a reliable and timely manner. Subsequent to the NPP mission, the Svalbard site and the high-speed fiber-optic link will also serve as one node in a distributed ground data communications system for NPOESS acquisition service.

The TT&C function uses S-band communications with uplink data rates of up to 32 kbit/s and downlink rates of up to 128 kbit/s. The NOAA network of polar ground stations will be used for mission operations (back-up TT&C services via TDRSS through S-band omni antennas on the satellite).

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Figure 7: Overview of Suomi NPP spacecraft communications with the ground segment (image credit: NASA) 20)


Suomi NPP broadcast services:

In addition, NPP will have a real-time HRD (High Rate Data) downlink in X-band (7812.0 MHz ± 0.03 MHz) direct broadcast mode to users equipped with appropriate field terminals. The objectives are to validate the innovative operations concepts and data processing schemes for NPOESS services. NPP world-wide users will already experience NPOESS-like data well in advance of the first NPOESS flight in 2013. The NPP broadcast services to the global user community are: 21) 22) 23) 24)

• X-band downlink at 30 Mbit/s

• Convolutional coding

• QPSK (Quadra-Phase Shift Keying) modulation

• An X-band acquisition system of 2.4 m diameter aperture is sufficient for all data reception. NASA will provide:

• Real-Time Software Telemetry Processing System

• Ground-Based Attitude Determination module

• Stand-alone Instrument Level-1 and select Level-2 (EDR) algorithms

• Instrument-specific Level 1 (SDR) & select Level-2 (EDR) visualization & data formatting tools

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Figure 8: The field terminal architecture of the NPP / NPOESS satellites (image credit: NASA, NOAA, IPO)

The DRL (Direct Readout Laboratory) of NASA/GSFC is committed to promote continuity and compatibility among evolving EOS direct broadcast satellite downlink configurations and direct readout acquisition and processing systems. The DRL bridges the EOS missions with the global direct readout community by establishing a clear path and foundation for the continued use of NASA’s Earth science DB data. The DRL is also involved in continued efforts to ensure smooth transitions of the Direct Broadcast infrastructure from the EOS mission to the next generation NPP (NPOESS Preparatory Project) and NPOESS (National Polar-orbiting Operational Environmental Satellite System) missions in the future. In an effort to foster global data exchange and to promote scientific collaboration, the DRL with support from other groups, is providing the user community access to Earth remote sensing data technologies and tools that enable the DB community to receive, process, and analyze direct readout data.

DRL developed IPOPP (International Polar Orbiter Processing Package), the primary processing package that will enable the Direct Readout community to process, visualize, and evaluate NPP and NPOESS sensor and EDRs (Environmental Data Records), which is a necessity for the Direct Readout community during the transition from the Earth Observing System (EOS) era to the NPOESS era. DRL developed also the NISGS (NPP In-Situ Ground System). The IPOPP will be: 25)

• Freely available

• Portable to Linux x86 platforms

• Efficient to run on modest hardware

• Simple to install and easy to use

• Able to ingest and process Direct Broadcast overpasses of arbitrary size

• Able to produce core and regional value-added EDR products.

Parameter

High Data Rate

Low Data Rate

Carrier frequency:

7812 MHz NPP
7834 MHz NPOESS


1707 MHz

Max occupied bandwidth: NPP
Max occupied bandwidth: NPOESS

30 MHz NPP
30.8 MHz


12.0 MHz

Channel data rate: (includes all CCSDS overhead, Reed-Solomon forward error correction, and convolutional encoding)

30 Mbit/s NPP
40 Mbit/s NPOESS


7.76 Mbit/s

Ground antenna aperture size

2-3 m

1 m

Minimum elevation angle

VIIRS compression

Lossless – RICE

Lossy – JPEG2000

Table 4: NPP & NPOESS Direct Readout link characteristics

Figure 9: High definition video of 'Earth From Space at Night' from the VIIRS instrument of the NASA/NOAA Suomi NPP Satellite (video credit: CoconutScienceLab, Published on Dec 10, 2012)




Mission status:

• August 10, 2019: Twin typhoons continued to churn across the Western Pacific Ocean late this week, threatening East Asian countries with destructive winds and rain. When this image was acquired on August 9, 2019, Typhoon Lekima (left) was skirting north of Taiwan and aiming for eastern China. 26)

- Although Taiwan avoided a direct hit from Typhoon Lekima, the storm’s outer bands still delivered strong rains and wind, causing flooding and power outages. According to China’s Central Weather Bureau, parts of the country’s northern mountains received as much as 390 mm (15 inches) of rain from 8-10 August. The rainfall increased the risk of landslides after a magnitude 6.0 earthquake rattled Taiwan on 8 August.

- Lekima next aimed for China’s Zhejiang Province. According to the Joint Typhoon Warning Center, the typhoon is expected to make landfall early on 10 August, about 325 km (200 miles) south of Shanghai. Forecasters expect it will then track northward. The cities labeled on the image all have populations of more than 1.5 million people.

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Figure 10: The image, captured by VIIRS on the Suomi NPP satellite, shows the storm on 9 August 2019 at 05:30 Universal Time (1:30 p.m. China Standard Time). Around that time, the storm was moving toward the northwest with maximum sustained winds of 105 knots (120 miles/195 km/hr), making it a category 3 storm on the Saffir-Simpson wind scale (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS data from NASA EOSDIS/LANCE and GIBS/Worldview, and the Suomi National Polar-orbiting Partnership. Story by Kathryn Hansen)

- Officials in China have issued a red alert, the highest of four levels on the country’s typhoon warning system. According to news reports, thousands of people in Shanghai were asked to prepare to evacuate. Transportation authorities have canceled large numbers of flights, halted trains, a rerouted cruise ships.

- Meanwhile, Typhoon Krosa (right) had maximum sustained winds of 85 knots (100 miles/155 km/hr), making it a category 2 storm when the image was acquired. Krosa continues to follow a more northerly path toward Japan, but the track forecasted for this storm remains uncertain.

• May 22, 2019: Some residents of the town of High Level, Canada, were told on May 20 to evacuate in the face of a large and out-of-control wildfire that has started advancing toward the town. 27)

- The Chuckegg Creek wildfire started on May 12, 2019, and mostly burned northwest and away from populated areas. On May 18, residents told news media about thick clouds of black smoke, an ominous sign but still a distant threat. By May 19, the fire had charred at least 25,000 hectares (60,000 acres), according to statistics from provincial officials at Alberta Wildfire.

- On May 20, the fire took a turn and advanced within 5 km of High Level (population 3,000). It had spread across an estimated 69,000 hectares, leading the Alberta Emergency Management Agency to issue a mandatory evacuation order for residents south and southeast of the town. A state of emergency was declared for Mackenzie County.

- Electric power outages were reported in High Level, First Nation reserves, and across parts of Mackenzie County. Fire managers warned of extreme fire danger due to warm air temperatures, low humidity, gusty winds, and no precipitation in the near-term forecast. Alberta Wildfire deployed more than 60 firefighters along with heavy equipment, helicopters, and air tankers to contain this fire, while requesting more resources from the province.

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Figure 11: VIIRS on the Suomi NPP satellite acquired this natural-color image of northern Alberta in the early afternoon of May 19, 2019. (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS data from NASA EOSDIS/LANCE and GIBS/Worldview, and the Suomi National Polar-orbiting Partnership. Story by Mike Carlowicz)

- The Chuckegg Creek wildfire was one of six burning out of control in northern and central Alberta Province as of May 20, 2019. The provincial government recorded 11 other fires as being under control and three as “being held” (not likely to grow past expected boundaries). Fire bans and off-road vehicle restrictions were in place in much of the northern tier of Alberta.

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Figure 12: VIIRS on the Suomi NPP satellite acquired this natural-color image of northern Alberta in the early afternoon of May 19, 2019 (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS data from NASA EOSDIS/LANCE and GIBS/Worldview, and the Suomi National Polar-orbiting Partnership. Story by Mike Carlowicz)

- The fires have sprung up in a time that ecologists refer to as the “spring dip.” Scientists have noted for years that forests in Canada and around the Great Lakes in the United States are especially susceptible to fire in the late spring because trees and grasses reach a point of extremely low moisture content (a dip) between the end of winter and the start of new seasonal growth. The effect is not yet well understood, as it also involves subtle changes in plant chemistry.

• May 07, 2019: It is not even summertime, but already the United Kingdom has seen a significant number of wildfires. The map above shows cumulative fire detections across the United Kingdom from January 1 through April 30, 2019. The data come from the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite. 28)

- Each red dot depicts one fire detection from the VIIRS 375-meter active fire data product. A “fire detection” is a pixel in which the sensor and an algorithm indicated there was active fire on any given day. Many fire detections can be generated by a single burning fire.

- Notable fires this year include blazes in February and April in England’s Ashdown Forest—the setting that inspired the Hundred Acre Wood in A.A. Milne’s Winnie the Pooh stories. In late February, following the United Kingdom’s warmest winter day on record, the Marsden Moor fire burned in West Yorkshire, England. Scotland has seen burning too, including a major wildfire that burned near a wind farm in Moray.

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Figure 13: Fires in the UK, detected by the VIIRS instrument on Suomi NPP in the period January 1 - April 30, 2019 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from the Suomi National Polar-orbiting Partnership. Story by Kathryn Hansen)

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Figure 14: This chart shows that there is a seasonal trend to the number of fire detections. Vegetation that was previously frozen and dried during the winter becomes fuel for wildfires during spring and summer months (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from the Suomi National Polar-orbiting Partnership. Story by Kathryn Hansen)

- Notice that there have been more fire detections since 2017 compared with previous years. According to the annual report on forest fires by the European Commission’s Joint Research Center, warm, dry weather was responsible for the rise in wildfire numbers across the United Kingdom in 2017. A similar situation played out in 2018.

- “Drier-than-normal conditions can boost fire detections in two ways,” said Wilfrid Schroeder, a scientist at the University of Maryland and principal investigator for the VIIRS active fire product. He noted that dry conditions favor the ignition and spread of fire. There also tends to be less cloud coverage, making fires more likely to be detected from space.

- High fire counts and warm, dry weather have been a continuing trend. By the end of April 2019, the United Kingdom had already seen more fires through this point in the year than in the record-breaking year of 2018.

• May 01, 2019: Between November and April, Harmattan trade winds carry vast amounts of mineral dust from the Sahara Desert across West African skies toward the Gulf of Guinea. The pall of dust that hangs over the region is known as the Harmattan haze—which, fittingly, means “tears your breath apart” in Twi, a common West African language. 29)

- West Africans have long known the haze season to be one of dry skin and chapped lips, but a recent study led by Susanne Bauer of NASA’s Goddard Institute for Space Studies suggests that dusty skies are more than a nuisance. Her analysis indicates that they are deadly for hundreds of thousands of people each year.

- Bauer became focused on the health impacts of dust somewhat indirectly. After completing a study in 2015 that found fertilizer use on farms was a surprisingly large source of air pollution, she wondered if there were other unexpected ways that food production was affecting air quality.

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Figure 15: The VIIRS instrument on the Suomi NPP satellite acquired this image of dust spreading across West Africa on February 2, 2019. One of the largest sources of dust in the Sahara is the Bodélé Depression, a dried lake-bed in northern Chad that is rich with silt and fine-grained dust. The alignment of nearby mountain ranges functions like a wind tunnel, funneling strong winds over the depression on a regular basis (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from the Suomi NPP. Story by Adam Voiland)

- This prompted her to look closely at fires in Africa. Every year, satellites detect thousands of manmade fires that come and go in sync with the seasons. Most of these fires are ignited to clear or fertilize crops, kill pests, and manage grasslands.

- Agricultural fires generate so much smoke that Bauer guessed they were one of the biggest sources of fine aerosol particles (PM2.5)—the particle size that causes the most serious health problems. (Fine particles can penetrate more easily into the human respiratory and circulatory system than larger particles.)

- Bauer and colleagues tried to confirm her suspicion by running a computer simulation of how smoke, desert dust, industrial haze, and other airborne particles (aerosols) moved and evolved in African skies with changing weather and environmental conditions. The model simulated conditions in 2016, a year when researchers had ample data from satellites and from field campaigns.

- To Bauer’s surprise, the analysis showed that the smoke had a smaller effect on people’s health than dust. “What we have is one of the most prolific sources of dust in the world—the Sahara Desert—regularly blowing large amounts of dust into densely populated countries in West Africa,” she explained. “When all of the dust mixes with air pollution from vehicles and factories in cities, the air becomes extremely unhealthy.” In contrast, smoke from crop fires tends to be concentrated in rural areas with relatively few people.

- By combining the results of several simulations with information about the health effects of breathing fine particles, Bauer and colleagues concluded that air pollution in Africa likely caused the premature deaths of about 780,000 people in 2016, more than the number killed by HIV/AIDS. They attributed about 70 percent of these deaths to dust, 25 percent to industrial pollution, and just 5 percent to smoke from fires. The effects of dust were especially pronounced in West African nations including Nigeria and Ghana.

- “Air pollution is of overwhelming importance to public health in Africa, yet it is hardly on the radar in most countries,” said Bauer. “Except in South Africa, there are virtually no routine measurements of PM2.5; few people understand that too much exposure to air pollution can shorten lives.”

• April 17, 2019: Don’t blink or you might miss some of Earth’s most spectacular transitions. As spring tightens its grip on the Northern Hemisphere, natural events like rainfed wildflower blooms, wind-stirred sediment swirls, and melting lake ice can fade as fast as they formed. 30)

- How long will it take Lake Balkash to become entirely ice free? In the past, the full transition has happened in a matter of weeks; check out this image pair from April 11 and 18, 2003. Water and air temperatures at this time of year are climbing, and the region is commonly windy, which can help break up lake ice.

- Notice that in areas where ice has already released its grip, the water appears in brilliant turquoise. That’s in part because the lake is extremely shallow—averaging 4.3 meters deep on the western side—which makes it easier for winds to stir up sediments from the bottom.

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Figure 16: Lake Balkhash, spanning about 17,000 km2 (6,600 square miles) in southeastern Kazakhstan, is one of Asia’s largest lakes. Despite the lake’s large size, winters are harsh enough to keep the lake frozen over from November through March. By April 8, 2019, when the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP acquired this image, the spring thaw was underway. Images from just a week before show the lake almost entirely covered with ice (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from the Suomi National Polar-orbiting Partnership. Story by Kathryn Hansen)

- Most of the water feeding the western portion of the lake comes from the Ili River, which is fed by meltwater runoff originating in the Tien Shan Mountains. (Part of that mountain chain, the Borohoro Range, is pictured with caps of snow and ice.) Research has found that degrading glaciers and melting snow in the Tien Shan have led to increases in the water level of Lake Balkash in recent decades. However, the authors note that if glacier degradation and melt continue, water level increases could quickly shift to decreases.

• April 16, 2019: For the second time in a month, an intense spring “bomb cyclone” plastered the Upper Midwest of the United States with snow and wind. While the April storm was not quite as strong as the blizzard in March, several states were hit with more than 12 inches (30 cm) of snow and by wind gusts exceeding 50 miles (80 km) per hour. 31)

- On April 10-12, 2019, whiteout conditions clogged roadways, caused tens of thousands of homes to lose power, and grounded hundreds of flights, according to news reports. South Dakota was one of the hardest hit states, with more than 24 inches (60 cm) of snow falling across much of the state.

- Many rivers in the region were already swollen with water (dark blue) before the storm arrived. Forecasters are wary that the influx of new snow could trigger new floods in the coming weeks; at a minimum, rivers will be high in the coming days. A few rivers in South Dakota—most notably the James and Big Sioux—were well above flood stage on April 15.

- The storm’s reach extended well beyond the Upper Midwest. As it pushed across the middle of the continent, it pulled in warm, dry air from the Southwest. Several meteorologists noted that it carried enough dust from Texas to color the snow in South Dakota and Minnesota in shades of yellow, brown, and orange.

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Figure 17: On April 8 and 13, 2019, the VIIRS instrument on the Suomi NPP satellite captured these false-color images. With this combination of visible and infrared light (bands M11-I2-I1), snow appears light blue and clouds white. Bare land is brown. You can see a natural-color version of the image here (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from the Suomi NPP, Story by Adam Voiland)

• April 9, 2019: In late March 2019, tropical cyclone Veronica made landfall along the Pilbara coast in Western Australia. Dropping more than 46 cm (18 inches) of rain in some areas within 72 hours, the storm caused major flooding and spurred several home evacuations. The destructive winds and the rainfall runoff also stirred up offshore waters, with lingering effects. 32)

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Figure 18: This image shows discolored water offshore from Port Hedland on March 29, 2019, as observed by the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on Suomi NPP. The satellite imagery shows what is likely a combination of suspended sediment and phytoplankton blooms appearing by March 27 and continuing through April 2, 2019 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from the Suomi National Polar-orbiting Partnership data from NASA EOSDIS/LANCE. Story by Kasha Patel)

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Figure 19: The Australian Bureau of Meteorology reported that a phytoplankton bloom was taking place at the time. This image shows concentrations of chlorophyll, the pigment that phytoplankton use to harvest sunlight, as derived by the Moderate Resolution Imaging Spectroradiometer (MODIS) on March 29, 2019 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kasha Patel)

- Past studies have shown that cyclonic winds can stir up ocean waters and bring nutrients to the surface, promoting blooms of phytoplankton. In coastal waters, nutrients often come from the resuspension of seafloor sediments and from river runoff.

- “Sometimes you can see a bloom last for many days over the open ocean after a tropical cyclone has passed,” said Sen Chiao, meteorologist at San Jose State University and director of the NASA-funded Center for Applied Atmospheric Research and Education. Chiao added that Veronica seems to have pulled cooler water up from the ocean depths to the surface (upwelling), which provided more nutrients.

- A similar bloom also followed a tropical cyclone a few years ago in the same region of Western Australia.

• March 26, 2019: On March 15, 2019, Tropical Cyclone Idai pummeled through eastern Africa causing catastrophic flooding, landslides, and large numbers of causalities across Mozambique, Malawi, and Zimbabwe. More than half a million people in Mozambique were affected, with the port city of Beira experiencing the most damage.33)

- The nighttime images of Beira’s nighttime lights (Figure 20) are based on data captured by the Suomi NPP satellite. The data were acquired by the VIIRS (Visible Infrared Imaging Radiometer Suite) “day-night band,” which detects light in a range of wavelengths from green to near-infrared, including reflected moonlight, light from fires and oil wells, lightning, and emissions from cities or other human activity. The base map makes use of data collected by the Landsat satellite.

- Note that these maps are not showing raw imagery of light. A team of scientists from NASA’s Goddard Space Flight Center and Marshall Space Flight Center processed and corrected the raw VIIRS data to filter out stray light from the Moon, fires, airglow, and any other sources that are not electric lights. Their processing techniques also removed as much other atmospheric interference—such as dust, haze, and thin clouds—as possible.

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Figure 20: The image on the left shows the extent of electric lighting across Beira on March 9, 2019, a typical night before the storm hit; the image on the right shows light on March 24, 2019, three days after Idai had passed. Most of the lights in Manga, Matacuane, and Macuti appeared to be out. According to news reports, the storm destroyed nearly 90 percent of the city (image credit: NASA Earth Observatory, images by Joshua Stevens, using Black Marble data courtesy of Ranjay Shrestha/NASA Goddard Space Flight Center, and Landsat data from the U.S. Geological Survey. Story by Kasha Patel)

• March 23, 2019: Two severe tropical cyclones bore down on northern Australia at the start of autumn 2019. Cyclone season in the region stretches from November to April, peaking in February and March. 34)

- Cyclone Trevor first made landfall on the Cape York Peninsula as a category 3 storm on March 20. The storm weakened and meandered over land before intensifying again to a category 4 storm over the warm waters of the Gulf of Carpentaria (about 31 degrees Celsius). The government of the Northern Territory declared a state of emergency and launched the largest evacuation in the state since 1974.

- Trevor is predicted to make landfall again on March 23, bringing intense winds, a storm surge, and widespread rainfall of 100 to 200 mm (4 to 8 inches), with some areas seeing up to 300 mm (12 inches). Some inland desert areas could see as much rain in a few days as they receive across some entire years.

- At the same time, Cyclone Veronica was approaching Western Australia and headed for possible landfall on the Pilbara Coast by March 23 or 24. Veronica developed from a tropical low pressure system to a category 4 storm on March 20. The Australian Bureau of Meteorology has advised: “Widespread very heavy rainfall conducive to major flooding is likely over the Pilbara coast and adjacent inland areas over the weekend. Heavy rainfall is expected to result in significant river rises areas of flooding and hazardous road conditions.”

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Figure 21: On March 22, 2019, VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite acquired the data to make this composite image. The seam line across Australia marks the edge of two different early afternoon satellite passes over the continent. At the time of the image, cyclones Trevor and Veronica both had sustained winds of roughly 175 km/hr (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from Suomi NP, story by Mike Carlowicz)

• February 28, 2019: The Manaro Voui volcano on the island of Ambae in the nation of Vanuatu in the South Pacific Ocean made the 2018 record books. A NASA-NOAA satellite confirmed Manaro Voui had the largest eruption of sulfur dioxide that year. 35) 36)

- The volcano injected 400,000 tons of sulfur dioxide into the upper troposphere and stratosphere during its most active phase in July, and a total of 600,000 tons in 2018. That’s three times the amount released from all combined worldwide eruptions in 2017.

- During a series of eruptions at Ambae in 2018, volcanic ash also blackened the sky, buried crops and destroyed homes, and acid rain turned the rainwater, the island’s main source of drinking water, cloudy and “metallic, like sour lemon juice,” said New Zealand volcanologist Brad Scott. Over the course of the year, the island’s entire population of 11,000 was forced to evacuate.

- At the Ambae volcano’s peak eruption in July, measurements showed the results of a powerful burst of energy that pushed gas and ash to the upper part of the troposphere and into the stratosphere, at an altitude of 10.5 miles. Sulfur dioxide is short-lived in the atmosphere, but once it penetrates into the stratosphere, where it combines with water vapor to convert to sulfuric acid aerosols, it can last much longer — for weeks, months or even years, depending on the altitude and latitude of injection, said Simon Carn, professor of volcanology at Michigan Tech.

- In extreme cases, like the 1991 eruption of Mount Pinatubo in the Philippines, these tiny aerosol particles can scatter so much sunlight that they cool the Earth’s surface below.

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Figure 22: This map shows stratospheric sulfur dioxide concentrations on July 28, 2018, as detected by OMPS on the Suomi-NPP satellite, when Ambae was at the peak of its sulfur emissions. For perspective, emissions from Hawaii’s Kilauea and the Sierra Negra volcano in the Galapagos are shown on the same day (image credit: Image by Lauren Dauphin, NASA Earth Observatory, using OMPS data from GES DISC and Simon Carn)

- The OMPS nadir mapper instruments on the Suomi-NPP and NOAA-20 (JPSS-1) satellites contain hyperspectral ultraviolet sensors, which map volcanic clouds and measure sulfur dioxide emissions by observing reflected sunlight. Sulfur dioxide (SO2) and other gases like ozone each have their own spectral absorption signature, their unique fingerprint. OMPS measures these signatures, which are then converted, using complicated algorithms, into the number of SO2 gas molecules in an atmospheric column.

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Figure 23: The plot shows the July-August spike in emissions from Ambae (image credit: Image by Lauren Dauphin, NASA Earth Observatory, using OMPS data from GES DISC and Simon Carn)

- “Once we know the SO2 amount, we put it on a map and monitor where that cloud moves,” said Nickolay Krotkov, a research scientist at NASA Goddard’s Atmospheric Chemistry and Dynamics Laboratory.

- These maps, which are produced within three hours of the satellite’s overpass, are used at volcanic ash advisory centers to predict the movement of volcanic clouds and reroute aircraft, when needed.

- Mount Pinatubo’s violent eruption injected about 15 million tons of sulfur dioxide into the stratosphere. The resulting sulfuric acid aerosols remained in the stratosphere for about two years, and cooled the Earth’s surface by a range of 1 to 2 degrees Fahrenheit.

- This Ambae eruption was too small to cause any such cooling. “We think to have a measurable climate impact, the eruption needs to produce at least 5 to 10 million tons of SO2,” Carn said.

- Still, scientists are trying to understand the collective impact of volcanoes like Ambae and others on the climate. Stratospheric aerosols and other volcanic gases emitted by volcanoes like Ambae can alter the delicate balance of the chemical composition of the stratosphere. And while none of the smaller eruptions have had measurable climate effects on their own, they may collectively impact the climate by sustaining the stratospheric aerosol layer.

- “Without these eruptions, the stratospheric layer would be much, much smaller,” Krotkov said.

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Figure 24: The natural-color image above was acquired on July 27, 2018, by the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP (image credit: Lauren Dauphin, NASA Earth Observatory)

• January 28, 2019: Large fires fueled by extremely dry and hot conditions have been burning for almost two weeks in central and southeast Tasmania, the southernmost state of Australia. This image was acquired on January 28, 2019, by the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite. 37)

- As of January 28, the Tasmania Fire Service reported 44 fires. The Great Pine Tier fire in the Central Plateau had burned more than 40,000 hectares. The Riveaux Road fire in the south had burned more around 14,000 hectares. News outlets reported smoke from some of the fires was visible as far away as New Zealand.

- The Tasmania Fire Service issued several emergency warnings to residents to relocate, as dangerous fire conditions and strong wind persist.

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Figure 25: Suomi NPP image of the southernmost island state of Australia, located 240 km to the south of the Australian mainland, captured on 28 January 2019 with VIIRS instrument showing the various fires (image credit: NASA Earth Observatory image by Lauren Dauphin, using VIIRS data from Suomi NPP, text by Kasha Patel)

• November 21, 2018: From sunset to sunrise, brilliant auroras—also known as the Northern Lights—provided a dazzling light show for Alaskans on 5 November 2018. Seven days later, they appeared again over Alaska and Canada. Those dancing lights were also visible from space. 38)

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Figure 26: This image shows the aurora over Alaska very early on 5 November 2018. The light was so bright that it illuminated the terrain below. The aurora likely appeared brighter that night because it occurred two days before a new moon, meaning the sky was darker than at other times in the lunar cycle (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS day-night band data from the Suomi NPP, story by Kasha Patel)

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Figure 27: The image shows the aurora over eastern Canada on 12 November 2018. Satellite imagery and ground reports indicate the aurora was also visible from Alaska, Norway, and Scotland around that time (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS day-night band data from the Suomi NPP, story by Kasha Patel)

- Both images were acquired by the VIIRS instrument on the Suomi NPP satellite. VIIRS has “day-night band” (observing mode) that detects city lights and other nighttime signals such as auroras, airglow, and reflected moonlight. In these images, the sensor detected the visible light emissions that occurred when energetic particles rained down from Earth’s magnetosphere and into the gases of the upper atmosphere.

- These auroras come at a time known as solar minimum, a relatively calm period of activity on the Sun that occurs every 11 years or so. During this time, the Sun experiences fewer sunspots and solar flares—phenomena that can lead to auroras.

- During a solar minimum, however, auroras are more often caused by coronal holes. These regions of open-ended magnetic fields allow relatively fast streams of solar particles to escape the Sun. This high-speed stream can energize our space environment, shaking Earth’s magnetic bubble enough to trigger auroral displays.

- Both auroras were caused by high-speed streams, though from different coronal holes. The coronal hole that sparked the 5 November aurora was particularly notable because it has been persistent for months, said Mike Cook, space weather forecaster lead at Apogee Engineering and team member of the citizen science project Aurorasaurus. This coronal hole first appeared in August 2018, and it has sent high-speed streams toward Earth and caused at least four fairly strong geomagnetic storms around Earth. NASA satellites are currently observing the Sun and Earth to see what may be in store when this coronal hole and others turn toward Earth again.

• November 02, 2018: Hazy skies have become an autumn tradition of sorts for the residents of several states in northern India. Each October and November, usually around the time of Diwali celebrations, a pall of smoke hangs over large swaths of the Indo-Gangetic Plain. 39)

- While industrial pollution contributes to the haze, most of it comes from crop-burning—especially in the states of Punjab and Haryana, where rice and wheat are widely grown. Burning typically peaks during the first week of November, a time when many farmers set fire to leftover rice stalks and straw after harvest, a practice known as stubble or paddy burning.

- Stubble burning is a relatively new phenomenon in northern India. Historically, farmers harvested and plowed fields manually, tilling plant debris back into the soil. When mechanized harvesting (using combines) started to become popular in the 1980s, burning became common because the machines leave stalks that are several inches tall. Burning is considered the quickest and cheapest way to clear the debris and prepare for the wheat crop.

- This year, Earth-observing satellites began to detect significant numbers of fires in early October near the town of Amritsar. By the end of the month, large numbers of fires burned across much of the states of Punjab and Haryana. The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured a natural-color image on the afternoon of October 31, 2018. The map (second image) shows the locations of fires detected by VIIRS during a 48-hour period from October 30 to November 1.

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Figure 28: VIIRS image of northern India acquired on 31 October 2018 (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS data from Suomi NPP)

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Figure 29: VIIRS image of northern India acquired on 01 November 2018 (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS data from Suomi NPP and the Fire Information for Resource Management System (FIRMS). Story by Adam Voiland)

- Despite efforts to curb the practice, crop burning is growing more common with each passing year. NASA’s Aqua satellite found a roughly 300 percent increase in the number of fires in the Indo-Gangetic Plain between 2003 and 2017, according to an analysis authored by Sudipta Sarkar, a scientist at NASA’s Goddard Space Flight Center.

- “It is easy to come up with regulations on paper, but you have to remember that many of these farms are relatively small-scale operations,” said Sarkar. “Without cheap, easy alternatives, there is little incentive for farmers to stop burning.”

- While smoke from the fires has the most direct consequences in northern India, Sarkar and colleagues found that harmful particles and gases regularly traveled several hundred miles from the source, sometimes affecting central and southern India.

- More widespread availability and use of farm equipment that removes the stalks and shreds the debris could eventually reduce farmers’ reliance on burning. But in the short term, people and other cities downwind ought to be prepared for more smoke.

- “The fire counts are rising, and so are particulate matter (PM2.5) levels in New Delhi,” said Hiren Jethva, a Universities Space Research Association scientist based at NASA’s Goddard Space Flight Center. He tracks the burning with several satellite sensors each year, and he recently noted: “The peak this year is expected to be between October 31 and November 6. Be prepared and take a good care of yourself, northern India.”

• October 29, 2018: Of the thousands of thermal anomalies that VIIRS detects each night, the vast majority are caused by fires. “But obviously a fire isn’t burning in the middle of the ocean,” said Patricia Oliva, a scientist at Universidad Mayor (Santiago de Chile) who helped develop a fire detection algorithm for VIIRS when she was at the University of Maryland. Natural gas flares also trigger thermal anomalies, but they are only found in shallow waters near the coast. Volcanic activity can light up the satellite as well, but there are no volcanoes anywhere near this area. 40)

- “It is almost certainly SAMA,” Oliva said, using an acronym for the South Atlantic Magnetic Anomaly. This weakness in Earth’s magnetic field, centered over South America and the South Atlantic, allows one of Earth’s Van Allen radiation belts—zones of energetic particles trapped by the magnetic field—to dip closer to the atmosphere. As a result, much of South America and part of the South Atlantic Ocean get an extra dose of radiation.

- While the atmosphere blocks most high-energy particles, and they do not cause problems at the surface, there are enough of them in the space close to Earth to cause issues for the electronics systems of spacecraft. The International Space Station has extra shielding because of SAMA, and the Hubble Space Telescope powers down its science instruments when it passes through the region.

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Figure 30: High-energy particles from the South Atlantic Magnetic Anomaly occasionally trick satellite sensors. On July 14, 2017, VIIRS on the Suomi NPP satellite captured this night image of the South Atlantic. The red dot several hundred kilometers off the coast of Brazil is a thermal anomaly—an area of Earth’s surface flagged by the satellite as being unusually warm (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS day-night band data from the Suomi NPP mission, story by Adam Voiland)

- In the case of VIIRS, there are enough energetic particles zipping around in the atmosphere around South America that the highly-sensitive radiometer detects some of them. In fact, the team developing the VIIRS active fire data product was surprised at how often the particles showed up as fires when they first began to process the data.

- “Each night, the sensor was detecting several dozen thermal anomalies over the Atlantic Ocean in places that didn’t make sense,” said Wilfrid Schroeder, the principal investigator for the VIIRS active fire product. The scientists were aware of this type of anomaly because researchers working with NASA’s MODIS sensor and the European Space Agency’s Advanced Along Track Scanning Radiometer (ATSR) satellite had encountered it. But the VIIRS team did not anticipate picking up on so many spurious fire signals.

- Their response was to build a series of filters into their active fire algorithm and remove false signals in this region. Suspicious thermal anomalies that are especially weak, over the ocean, and short-lived—all signs that they were caused by SAMA instead of a real fire—get removed by the algorithm.

- But occasionally a stray SAMA pixel still slips through the filters. “We see probably one or two of these spurious fire detections a night, but remember that is in comparison to the thousands of real thermal anomalies satellite detects each night,” said Schroeder. “False fires detections are quite rare.”

- “In developing an algorithm like this for a global data product, we had to find a balance. If we are too aggressive with our filtering, there is a risk that we will remove real fires from the data record,” said Oliva. “I don’t think people realize that most satellite data products go through a whole battery of calibration and validation tests to address issues like this.”

• October 6, 2018: No, this is not an image of a jellyfish (Figure 31) drifting in the ocean’s twilight zone. It is a satellite image of a cloud hovering over Earth’s surface at night. The peculiar shape is the product of an outflow boundary associated with a decaying thunderstorm over Mali. 41)

- Thunderstorms often develop on hot days as warm air rises and the moisture condenses into towering cumulus and cumulonimbus clouds with downpours and lighting at their centers. The falling rain cools the air and creates a downdraft that spreads outward in a circular fashion once it reaches the ground—much like pancake batter spreads out after being poured onto a griddle.

- The outflow boundary, sometimes called a gust front, is the leading edge of a spreading pool of cool air near a thunderstorm. Outflow boundaries can persist for many hours after a thunderstorm, and they can travel hundreds of kilometers from where they formed.

- “In this case, the fact that the outflow boundary is only present on one side of the storm is a result of wind shear in the environment,” explained Joseph Munchak, a research meteorologist based at NASA’s Goddard Space Flight Center. (Wind shear arises from differences in wind speed or direction with height.) “The arc-shape line of clouds is caused by less dense air being lifted up and over the boundary.”

- Gust fronts sometimes carry ominous-looking shelf and roll clouds that signal the arrival of stormy weather. In dusty areas, they can stir up walls of dust known as haboobs. Outflow boundaries can even sweep up enough flying insects, birds, and other debris that the collection of creatures and debris shows up on weather radar. The choppy winds in outflow boundaries can pose serious problems for aircraft trying to take off or land.

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Figure 31: The peculiar curved shape of this cloud over Mali is the product of a phenomenon associated with thunderstorms. The image was acquired by the “day-night band” (DNB) on VIIRS (Visible Infrared Imaging Radiometer Suite) on Suomi NPP early on 27 September 2018. The DNB sensor detects dim light signals such as auroras, airglow, and city lights (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS day-night band data from the Suomi NPP mission, story by Adam Voiland)

• September 16, 2018: In the early hours of September 15, 2018, Super Typhoon Mangkhut (Ompong) blew into Cagayan Province near the northern tip of Luzon, one of the most populated of the Philippine islands. Local reports described wind speeds of 205 km/hr. The storm stretched nearly 900 km across, with an eye 50 km wide. It is the strongest tropical cyclone in any ocean basin so far this year. 42)

- Luzon is a major corn and rice-growing region of the Philippines, and it is nearly time for the harvest. News agencies reported than at least 4 million people were in the path of the storm, and thousands were evacuated from coastal lowlands before Mangkhut arrived. Forecasters from PAGASA were predicting storm surges up to 6 meters and exceptional rainfall.

- On September 14, 2018, VIIRS ( Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite acquired a natural-color image of Mangkhut just after midday. At 8 p.m. Philippine Standard Time (12:00 Universal Time) on September 14, the U.S. Joint Typhoon Warning Center reported that the storm still had sustained winds of 145 knots (165 miles/270 km per hour), with gusts to 175 knots. Maximum significant wave heights were 12 meters.

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Figure 32: The super typhoon made landfall on the northernmost island in the Philippine archipelago. VIIRS acquired this image on 14 September 2018 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from Suomi NPP, story by Mike Carlowicz)

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Figure 33: This false-color image of VIIRS, acquired on 14 September, shows infrared signals known as brightness temperature. This is useful for distinguishing cooler (dark) cloud tops from the warmer (whiter) clouds and water surfaces below (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from Suomi NPP, story by Mike Carlowicz)

• September 12, 2018: Most of us are familiar with heat waves on land, but in a warming world, heat waves are starting to become common in the ocean, too. One basin in particular, the normally cool Gulf of Maine in the Northwest Atlantic Ocean, has seen several heat waves in recent years and has spent most of 2018 with unusually warm water temperatures. 43)

- On August 8, 2018, scientists using satellite data and sea-based sensors measured the second warmest sea surface temperatures ever observed in the Gulf of Maine. Average water temperatures reached 20.52º Celsius (68.93º Fahrenheit) that day, just 0.03°C (0.05°F) below the record set in 2012.

- The heatwave of 2018 fits with a much longer trend in the region, which is among the fastest-warming parts of the global ocean. In the past three decades, the Gulf of Maine has warmed by 0.06°C (0.11°F) per year, three times faster than the global average. Over the past 15 years, the basin has warmed at seven times the global average. The Gulf has warmed faster than 99 percent of the global ocean.

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Figure 34: This map as well as Figure 35 show sea surface temperature anomalies as compiled by NOAA’s Coral Reef Watch, which blend observations from the Suomi NPP, MTSAT, Meteosat, and GOES satellites and from computer models. Shades of red and blue indicate how much water temperatures were above or below the long-term average for the region. This map shows conditions on August 8, the near-record setting day, while the map below shows conditions across the entire month of August 2018 (image credit: NASA Earth Observatory, images by Lauren Dauphin, and sea surface temperature data from Coral Reef Watch. Story by Michael Carlowicz)

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Figure 35: The heatwave of 2018 fits with a much longer trend in the region, which is among the fastest-warming parts of the global ocean. In the past three decades, the Gulf of Maine has warmed by 0.06°C (0.11°F) per year, three times faster than the global average. Over the past 15 years, the basin has warmed at seven times the global average. The Gulf has warmed faster than 99 percent of the global ocean (image credit: NASA Earth Observatory, images by Lauren Dauphin, and sea surface temperature data from Coral Reef Watch. Story by Michael Carlowicz)

- “We’ve set 10 daily temperature records this summer, after setting 18 this winter,” said Andrew Pershing, chief scientist of the Gulf of Maine Research Institute (GMRI). “We’ve had to add new colors to our temperature illustrations to reflect just how warm the Gulf of Maine has been this year.”

- In recent years, oceanographers have come to define marine heatwaves as periods when water temperature rise above the 90th percentile (of average temperatures) for more than five days. In 2018, the Gulf of Maine has spent more than 180 days above the 90th percentile.

- The Gulf of Maine stretches from Cape Cod to Nova Scotia, and it is key intersection between cold water masses from the Arctic and warm water masses from the Gulf Stream. The warming trend in this basin likely has two main causes. First is the overall warming of the global ocean as air temperatures and greenhouse gas concentrations rise. Second is the melting of ice in Greenland and the Arctic Ocean, which provides pulses of fresh water that can alter ocean circulation patterns in the region.

- “We are seeing a major shift in the circulation in the North Atlantic, likely related to a weakening Atlantic Meridional Overturning Circulation (AMOC),” said Pershing. “One of the side effects of a weaker AMOC is that the Gulf Stream shifts northward and the cold current flowing into the Gulf of Maine gets weaker. This means we get more warmer water pushing into the Gulf.”

- “Climate change is likely contributing to the circulation changes through melting in Greenland and Arctic,” he added, “as well as making long-stretches of warm weather more likely.”

- The warming waters are already affecting marine species in the area, according to several news media and scientist accounts. Herring populations (based on fishing catches) seem to be down this year, and researchers and fishermen are seeing more species usually found in warmer waters, such as butterfish and squid. The populations of copepods, a key food source for endangered Northern Right Whales, also seem to be moving with the changing conditions. And puffins have had to adapt in feeding their chicks this year, as the newly common butterfish are too large for hatchlings to swallow.

• August 24, 2018: During one day in August, tropical cyclones, dust storms, and fires spread tiny particles throughout the atmosphere. Take a deep breath. Even if the air looks clear, it is nearly certain that you will inhale millions of solid particles and liquid droplets. These ubiquitous specks of matter are known as aerosols, and they can be found in the air over oceans, deserts, mountains, forests, ice and every ecosystem in between. 44)

- If you have ever watched smoke billowing from a wildfire, ash erupting from a volcano or dust blowing in the wind, you have seen aerosols. Satellites like NASA's Earth-observing satellites, Terra, Aqua, Aura and Suomi NPP, “see” them as well, though they offer a completely different perspective from hundreds of kilometers above Earth’s surface. A version of a NASA model called the Goddard Earth Observing System Forward Processing (GEOS FP) offers a similarly expansive view of the mishmash of particles that dance and swirl through the atmosphere.

- The visualization of Figure 36 highlights GEOS FP model output for aerosols on August 23, 2018. On that day, huge plumes of smoke drifted over North America and Africa, three different tropical cyclones churned in the Pacific Ocean, and large clouds of dust blew over deserts in Africa and Asia. The storms are visible within giant swirls of sea salt aerosol (blue), which winds loft into the air as part of sea spray. Black carbon particles (red) are among the particles emitted by fires; vehicle and factory emissions are another common source. Particles the model classified as dust are shown in purple. The visualization includes a layer of night light data collected by the day-night band of the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP that shows the locations of towns and cities.

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Figure 36: The aerosol in this visualization is not a direct representation of satellite data. The GEOS FP model, like all weather and climate models, used mathematical equations that represent physical processes to calculate what was happening in the atmosphere on August 23. Measurements of physical properties, like temperature, moisture, aerosols, and winds, are routinely folded into the model to better simulate real-world conditions (image credit: NASA Earth Observatory, image by Joshua Stevens, using GEOS data from the Global Modeling and Assimilation Office at NASA GSFC. Story by Adam Voiland)

Legend to Figure 36: Some of the events that appear in the visualization were causing pretty serious problems on the ground. On August 23, Hawaiians braced for torrential rains and potentially serious floods and mudslides as Hurricane Lane approached. Meanwhile, twin tropical cyclones—Soulik and Cimaron—(Figure 37) were on the verge of lashing South Korea and Japan. The smoke plume over central Africa is a seasonal occurrence and mainly the product of farmers lighting numerous small fires to maintain crop and grazing lands. Most of the smoke over North America came from large wildfires burning in Canada and the United States.

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Figure 37: The GEOS FP model for aerosols of the Asia region on 23 August 2018 (image credit: NASA Earth Observatory, image by Joshua Stevens, using GEOS data from the Global Modeling and Assimilation Office at NASA GSFC. Story by Adam Voiland)

• August 8, 2018: California has seen a range of natural extremes this summer, from heat waves to wildfires. The state can now add to the list record-warm ocean temperatures. On August 1, 2018, researchers from the Scripps Institution of Oceanography observed water temperatures of 25.9 degrees Celsius (78.6 degrees Fahrenheit) along the coast at La Jolla, exceeding the previous record of 25.8°C (78.4°F) set in 1931. 45)

- The warm water stretched far beyond La Jolla. The map of Figure 38 shows sea surface temperature anomalies on August 2, 2018, as compiled by NOAA’s Coral Reef Watch, which blends observations from the Suomi NPP, MTSAT, Meteosat, and GOES satellites and computer models. Mapping the temperature anomaly allows you to see how much the surface layer was above or below the long-term average temperature for this time of year. The warmest sea surface temperatures (red) extend from Point Conception to the Baja California coast. According to Bill Patzert, retired NASA climatologist, temperatures along this part of the coastline were 5-10°F above normal.

- “The primary driver of these warm ocean temperatures is the persistence of continental atmospheric high pressure that has dominated western weather,” Patzert said. He explained that normally, high pressure over the eastern Pacific Ocean drives winds from the north along the California coast. These winds push coastal surface waters offshore, allowing cool waters from below to “upwell” to the surface and keep coastal California cool.

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Figure 38: A layer of exceptionally warm surface water extended from Point Conception to the Baja California coast as recorded on 2 Aug. 2018 as compiled by NOAA’s Coral Reef Watch (image credit: NASA Earth Observatory, image by Lauren Dauphin, and sea surface temperature data from Coral Reef Watch. Story by Kathryn Hansen)

- This summer, however, a dome of high pressure over the continental west has dominated, causing coastal winds to blow from the south. This pattern has sustained a cap of warm ocean waters from San Diego to Santa Barbara, preventing cool water from rising up.

- Warm water for beachgoers and for nearshore ecosystems is not the only consequence of the high-pressure system. “This pattern is also driving the month-long heat wave suffocating California and it is a major cause of the explosion of Western wildfires,” Patzert said. “The continuing Western drought, July heat waves, explosive fire season, and balmy ocean temperatures are all related.”

• July 30, 2018: A persistent heatwave has been lingering over parts of Europe, setting record high temperatures and turning typically green landscapes to brown. 46)

- The image of Figure 39 show browning in north-central Europe on July 24, 2018. For comparison, the image of Figure 40 shows the same area one year ago. Both images were acquired by the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite.

- Peter Gibson, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory, examined how global temperatures have varied in June over the past 50 years, using historical temperature data from the NASA Goddard Institute for Space Studies. The data showed a steep, persistent warming trend over the decades, and extreme heatwaves are more common.

- “If the globe continues to warm, it’s clear we will continue to see events like this increasing in frequency, severity, and duration,” said Gibson, who recently published a study linking global temperatures to regional heatwaves. “We found that parts of Europe and North America could experience an extra 10 to 15 heatwave days per degree of global warming beyond what we have seen already.”

- Gibson said this particular heatwave has been boosted by an unusual positioning and persistence of the jet stream. Since May, the jet stream has been stationed unusually far north, particularly over Europe, and in a wavy pattern like the uppercase Greek letter omega. The upper level wind pattern has trapped an area of high pressure over the United Kingdom that has mostly been windless, cloudless, and very hot.

- “Scientists are still working out the details of how climate change might be influencing the jet stream. But we already know the background state of the climate has warmed by about 1°C, indicating some human influence on this event,” said Gibson.

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Figure 39: VIIRS image of north-central Europe on 24 July 2018 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from Suomi NPP from LANCE/EOSDIS Rapid Response. Story by Kasha Patel)

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Figure 40: VIIRS image of north-central Europe on 19 July 2017 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using VIIRS data from Suomi NPP from LANCE/EOSDIS Rapid Response. Story by Kasha Patel)

- According to the European Space Agency, these regions turned brown in just a month, during which several countries experienced record high temperatures and low precipitation. Much of Germany has experienced drought conditions since May. The United Kingdom experienced its driest first half of summer (June 1 to July 16) on record.

- The image pair of Figures 41 and 42 shows the burned landscape of the United Kingdom and northwestern Europe as of 15 July 2018, compared with 17 July 2017. Both images were acquired by the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra satellite.

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Figure 41: MODIS image of the landscape of the United Kingdom and northwestern Europe as of 15 July 15 2018 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from LANCE/EOSDIS Rapid Response. Story by Kasha Patel)

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Figure 42: MODIS image of the landscape of the United Kingdom and northwestern Europe as of 17 July 2017 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from LANCE/EOSDIS Rapid Response. Story by Kasha Patel)

• June 19, 2018: As weather grows hot and the winds pick up in late spring, dust storms start to blow across India. The most intense dust storms usually occur just before monsoon season. But this year has been worse than usual. 47)

- “Every year in April, May, and June, we see dust loading,” said Hiren Jethva, who studies aerosols with the Universities Space Research Association at NASA's Goddard Space Flight Center. “This year’s dust season, including this most recent event, has been unusual in terms of the intensity.”

- In May 2018, India experienced a period of extreme weather, including intense dust and lightning storms. A new burst of storms from June 12-15 over New Delhi led to severe pollution, causing citizens to suffer through poor breathing conditions.

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Figure 43: A dust storm originated in the western state of Rajasthan on June 12, 2018, as high winds kicked up dust from the Thar desert. Over the next few days, the dust traveled across north-central India. This image was acquired on June 14 by the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite. The dust was trapped between mountain ranges and appears in the shape of upside down “v” on the image (image credit: NASA Earth Observatory images by Lauren Dauphin, using VIIRS data from the Suomi NPP satellite)

- Jethva expected the dust to continue moving southeast toward the Bay of Bengal, but instead it stayed concentrated over the northern plain for another day because the south-moving dust was met by strong winds blowing northwest from the Bay of Bengal. Air quality around New Delhi was at its worst on June 15, 2018.

- Along with the strong southwesterly winds lifting dust into the air, one reason for the intense dust storm is that the first spell of monsoon rain has been delayed in northern India this year. Normally, the rains help dampen and remove dust, cleansing the air. The India Meteorological Department is forecasting light showers in New Delhi, which may alleviate the air pollution.

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Figure 44: This graph, acquired between 2-17 June 2018, shows air quality conditions (particulate matter and ground-level ozone) over New Delhi as reported by the U.S. Embassy and Consulates' air quality monitors. Hazardous levels of air quality are classified with measurement values of from 301 to 500. New Delhi’s air quality index on June 15th was around 518. The local government advised people to stay inside and deployed fire brigades to sprinkle water across the city (air quality data from AirNow (2018))

• June 8, 2018: In global satellite observations of sulfur dioxide (SO2), several sources of the polluting gas stand out. Dozens of volcanoes spit out plumes of it during explosive and effusive eruptions; the gas also seeps more or less continuously from dozens of other volcanoes that are not actively erupting in a process scientists call passive degassing. And nearly 300 coal-fired powered plants, dozens of gas and oil sites, and more than 50 smelting facilities emit streams of sulfur dioxide large enough to be detected from space. 48)

- But of all the manmade (anthropogenic) sources, one location really sticks out: Norilsk. This industrial city of 175,000 people in northern Siberia has several mines that tap into one of the largest nickel, copper, platinum, and palladium deposits on Earth. And all of the smelting—the extraction of usable metal from ore by grinding it up and melting it—that happens there has made it into one of the largest sources of sulfur dioxide detectable by satellites.

- OMPS (Ozone Mapping Profiler Suite) on the Suomi NPP satellite acquired the data for the map (Figure 45) of sulfur dioxide concentrations around the city on July 12, 2017. The map shows the gas observed in the boundary layer, the lowest part of the atmosphere. Emissions on this day were typical for a June summer day, maxing out at roughly 4 Dobson Units.

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Figure 45: Map of the SO2 polluted Norilsk region in northern Siberia acquired with OMPS on the Suomi NPP satellite on 12 July 2017 (image credit: NASA Earth Observatory, image by Joshua Stevens, using OMPS data from the Goddard Earth Sciences Data and Information Services Center (GES DISC), Story by Adam Voiland)

- Several teams of scientists have scrutinized Norilsk’s sulfur dioxide cloud because it is so extreme. “It is almost double the size of the next largest anthropogenic source,” said Chris McLinden, an atmospheric scientist with Environment and Climate Change Canada. “In fact, Norlisk’s emissions are more comparable to the passive degassing that happens at some of the most active effusive volcanoes. Between 2005 and 2017, only one volcano—Ambrym in Vanuata—emitted more sulfur dioxide through passive degassing than Norilsk.”

- Several research teams have quantified the sulfur dioxide emissions from Norilsk. One recent study based on OMI (Ozone Monitoring Instrument) data put the number between 1700 and 2300 metric kilotons (kT) per year. A separate estimate based on aircraft measurements tallied 1000 kT per year.

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Figure 46: The natural-color image of OLI on Landsat-8, acquired on 12 July 2017, browning vegetation around the city is visible northwest and southeast of the city. A bright pollution plume rich with sulfur dioxide drifted from a large smelting facility southwest of the city. The red color of the water of the tailings pond likely relates to nearby mining or smelting activities (image credit: NASA Earth Observatory, image by Joshua Stevens, using Landsat data from the USGS, Story by Adam Voiland)

- Whatever the number, none of the scientists who study Norilsk doubt that it is a lot of sulfur dioxide. Several researchers have documented widespread degradation of the forests surrounding Norilsk because of regular exposure to high levels of the gas. Sulfur dioxide causes the pores on leaves (stomata) to open up too much, resulting in the loss of water. Over time, leaves become bleached or discolored, and trees or other plants can become stunted or die as they struggle to generate energy through photosynthesis.

- Sulfur dioxide emissions have been intense at Norilsk for decades. The city began producing nickel and other metals in the 1940s. Satellites have closely monitored its sulfur dioxide emissions since the Aura satellite was launched in 2004. Since then, emissions from Norilsk have not changed much, even as other major smelting sites in Peru and Kazakhstan saw significant declines in sulfur dioxide thanks to modernization projects.

- There are signs that the days of large sulfur dioxide clouds hanging over the city may be numbered. Mine operators have described an ambitious plan to modernize equipment and potentially reduce sulfur dioxide emissions by 75 percent by 2023.

• June 5, 2018: Fuego in Guatemala is one of Central America’s most active volcanoes. For years, the towering Volcán de Fuego has puffed continuously, punctuated by occasional episodes of explosive activity, big ash plumes, lava flows, and avalanche-like debris slides known as pyroclastic flows. 49)

- Just before noon on June 3, 2018, the volcano produced an explosive eruption that sent ash billowing thousands of meters into the air. A deadly mixture of ash, rock fragments, and hot gases rushed down ravines and stream channels on the sides of the volcano. Since these pyroclastic flows often move at speeds of greater than 80 km/hr, they easily topple trees, homes, or anything else in their path. According to news reports, more than two dozen people were killed. As a precautionary measure, thousands of other people have been evacuated.

- In addition to ash, the plume contains gaseous components invisible to the human eye, including sulfur dioxide (SO2). The gas can affect human health—irritating the nose and throat when breathed in—and reacts with water vapor to produce acid rain. Sulfur dioxide also can react in the atmosphere to form aerosol particles, which can contribute to outbreaks of haze and sometimes cool the climate.

- Satellite sensors such as AIRS (Atmospheric Infrared Sounder) on the Aqua satellite and OMPS (Ozone Mapping Profiler Suite) on Suomi NPP make frequent observations of sulfur dioxide. The map (Figure 48) shows concentrations of sulfur dioxide in the middle troposphere at an altitude of 8 km as detected by OMPS on June 3.

- Upon seeing data collected by AIRS several hours after the eruption that showed high levels of sulfur dioxide in the upper troposphere, Michigan Tech vulcanologist Simon Carn tweeted that this appeared to be the “highest sulfur dioxide loading measured in a Fuego eruption in the satellite era.”

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Figure 47: VIIRS (Visible Infrared Imaging Radiometer Suite) on Suomi NPP acquired this image of the ash plume at 1 p.m. local time (19:00 UTC) on June 3, 2018, after the ash (brown) had punched through a deck of clouds. A report from the Washington Volcanic Ash Advisory Center estimated the plume’s maximum height at 15 km. Imagery from a geostationary satellite showed winds blowing the plume to the east. The eruption deposited ash on several communities surrounding the volcano, including Guatemala City, which is 70 km to the east (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS data from the Suomi NPP, story by Adam Voiland)

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Figure 48: The map shows concentrations of sulfur dioxide in the middle troposphere at an altitude of 8 km as detected by OMPS on Suomi NPP on June 3. The OMPS data is from the Goddard Earth Sciences Data and Information Services Center (GES DISC), image credit: NASA Earth Observatory, image by Joshua Stevens, story by Adam Voiland

• May 25, 2018: India has been hit by a streak of unusually intense thunderstorms, dust storms, and lightning so far in 2018. The events collapsed homes, destroyed crops, and claimed the lives of over a hundred people with even more casualties, calling for assistance by Prime Minister Narendra Modi. 50)

- In late April, the state of Andhra Pradesh in southeastern India was struck by about 40,000 lightning bolts in 13 hours—more than the number of strikes that occurred in the entire month of May 2017 — striking people and livestock.

- On May 2, 2018, a cluster of strong thunderstorms, accompanied by strong winds and lightning, swept through the Rajasthan region in the north, knocking over large structures and harming those in the way. The potent thunderstorms whipped up one of the deadliest dust storms in decades.

- One week later, the same region was hit by more deadly thunderstorms that brought lightning, 110 km/hour winds, and violent dust storms.

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Figure 49: This map shows aerosols, including dust, over northern India on May 14, 2018, around the time of the second dust storm. The aerosol measurements were recorded by OMPS (Ozone Mapping and Profiler Suite) on the Suomi NPP satellite. The dust is naturally blocked from moving north by the Himalayan mountain range. In addition to causing accidents and poor air quality, dust aerosols can influence the amount of heat transmitted to Earth‘s surface by either scattering or absorbing incoming sunlight (image credit: NASA Earth Observatory, image by Joshua Stevens, using OMPS data from NASA's NPP Ozone Science Team, story by Kasha Patel)

- In recent years, extreme weather events such as heat waves, thunderstorms, and floods have been increasing in India, according to Ajay Singh, a climate change researcher with the Indian Institute of Technology Bombay. “Overall, the impact of global warming on the climate of India is clearly visible in the form of increased frequency and intensity of most of the extreme weather events,” said Singh.

- Even with the increasing trend, the intensity of events so far this year is anomalous, said Singh. The unusual thunder and dust storms could have a combination of causes, including extra moisture from a cyclonic circulation over West Bengal colliding with destructive dusty winds. High temperatures in the area also made the atmosphere unstable, fueling thunderstorms and heavy winds.

- The unusually high number of lightning strikes was caused by cold winds from the Arabian Sea colliding with warmer winds from northern India, leading to the formation of more clouds than usual. The spike in lightning this April was abnormal, but India has long been prone to lightning strikes, which are believed to cause more fatalities than any other natural hazard in the country.

- Researchers are interested to learn how the spring 2018 lightning burst in India fits in with longer term trends. Some years can be highly active without signaling a trend, said Dan Cecil, a scientist at NASA Marshall. For instance, a region near Andhra Pradesh had almost double the normal lightning flash rates in 2010, yet 2011 was almost exactly normal. The following years alternated between being slightly below normal and slightly above normal, according to satellite data.

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Figure 50: This map shows the annual average number of lightning flashes in India from 1998–2013. The visualization was made from data acquired by the LIS (Lightning Imaging Sensor) on NASA’s TRMM (Tropical Rainfall Measuring Mission) satellite and compiled by the GHRC (Global Hydrology Resource Center). Southeastern India usually experiences increased lightning activity before a monsoon season, as heating and weather patterns become unstable and changeable (image credit: NASA Earth Observatory, image by Joshua Stevens, using lightning climatology data from GHRC Lightning & Atmospheric Electricity Research, story by Kasha Patel)

• May 9, 2018: Kilauea has been erupting continuously since 1983, but in late April and early May 2018 the volcanic eruption took a dangerous new turn. 51)

- During the last week of April, the lava lake at Halema‘uma‘u Overlook crater overflowed several times and then began to drain rapidly after the crater floor partially collapsed. Soon after, a swarm of earthquakes spread across Kilauea’s East Rift Zone as magma moved underground. On May 3, 2018, several new fissures cracked open the land surface in the Leilani Estates subdivision, leaking gases and spewing fountains of lava. As of May 7, 2018, slow-moving lava flows had consumed 35 homes in that community of 1,500 people.

- In addition to seismic activity and deformation of the land surface, another sign of volcanic activity is increased emission of sulfur dioxide (SO2), a toxic gas that occurs naturally in magma. When magma is deep underground, the gas remains dissolved because of the high pressure. However, pressure diminishes as magma rises toward the surface, and gas comes out of solution, or exsolves, forming bubbles in the liquid magma.

- “The process is similar to what happens when a bottle of soda is opened,” explained Ashley Davies, a volcanologist at NASA’s Jet Propulsion Laboratory. “The bubbles of sulfur dioxide and other volatiles, including water and carbon dioxide, begin to rise through the liquid magma and concentrate in the magma closest to the surface, so the first lava to erupt is often the most volatile-rich. There’s usually an increase in sulfur dioxide output right before lava reaches the surface, as the gas escapes from the ascending magma.”

- Sensors onboard the Ozone Mapping Profiler Suite (OMPS) sensor on the Suomi NPP satellite have begun to detect signs of activity at Kilauea. The series of images above shows elevated concentrations of sulfur dioxide on May 5, a few days after the new fissures opened up. The second chart (below) underscores the significant natural variability in sulfur dioxide emissions as observed by OMPS over Hawaii between January and May 2018.

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Figure 51: The growth of SO2 emissions during the volcanic activity on Kilauea, acquired with OMPS in the period April 30 - May 5, 2018 (NASA Earth Observatory images by Joshua Stevens, using OMPS data from the Goddard Earth Sciences Data and Information Services Center (GES DISC). Story by Adam Voiland, with information from Simon Carn (Michigan Tech), Nickolay Krotkov (NASA Goddard Space Flight Center), Ashley Davies (NASA Jet Propulsion Laboratory), Janine Krippner (Concord University), and Jean-Paul Vernier (NASA Langley Research Center).

- “Interpreting the satellite SO2 data for events like this is complicated because there are multiple SO2 sources that combine to form the volcanic sulfur dioxide plume. The Kilauea volcano has several sources of sulfur dioxide degassing: the summit caldera (a significant source since 2008); the Pu’u ‘O’o vent on the East Rift Zone; and now the new eruption site in Leilani Estates,” said Simon Carn, a volcanologist at Michigan Tech. “It can be very hard to distinguish individual ‘plumes’ from these sulfur dioxide sources with the spatial resolution that we have from OMPS, but we are seeing what seems to be an overall increase that coincides with the latest activity.”

- Another satellite-based sensor—ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) on NASA’s Terra satellite—observed SO2 emissions on May 6, 2018. When ASTER passed over Hawaii, the largest source of SO2 appeared to be coming from Kilauea’s summit crater, but there was also a sizable plume streaming southwest from the fissures in Leilani Estates. So far, trade winds have pushed the toxic gas offshore, but Hilo and other communities northwest of Leilani Estates could see air quality deteriorate if the trade winds weaken.

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Figure 52: Sulfur Dioxyde at Kilauea (Dobson units), acquired in the period January 1 - May 5, 2018 (image credit: NASA Earth Observatory)

• April 24, 2018: We know the Sun is the source and driver of so many things in our earthly days: providing light and heat that energize our plants, our solar panels, and our weather, among other things. But its influence stretches over the horizon into our nights, as well. As our nearest star, the Sun bathes Earth in a steady stream of energetic particles, magnetic fields, and radiation that can stimulate our atmosphere and light up the night sky. The most famous and beautiful example is the aurora borealis, or northern lights. 52)

- In the image of Figure 53, the sensor detected the visible light emissions that occurred as energetic particles from Earth’s magnetosphere rained down into the oxygen and nitrogen gases of the upper atmosphere. Around April 19, the Sun spewed a potent stream of particles and electromagnetic energy—a strong blast of solar wind—that arrived at Earth a few days later and stirred up our magnetic field. The interaction between these solar emissions and our magnetic field causes the particles already trapped around the planet to be accelerated down toward the atmosphere. The collisions make the auroral light.

- Scientists recently discovered a new type of atmospheric light emission related to auroras and known as strong thermal emission velocity enhancements. STEVE is a thin purple ribbon of light that can appear in the presence of an aurora, although it was not reported during the April 21 event. You can participate in a citizen-science project to track auroras and help find new observations of STEVE through Aurorasaurus.

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Figure 53: At 2:46 a.m. Central Daylight Time (07:46 Universal Time) on April 21, 2018, VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite acquired this image of the aurora borealis over North America. The nighttime image was made possible through VIIRS “day-night band,” which detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe signals such as airglow, auroras, wildfires, city lights, and reflected moonlight (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS day-night band data from the Suomi National NPP, story by Mike Carlowicz)

• April 7, 2018: As is often the case in the spring, satellites detected dozens of fires burning in Russia’s far eastern Amur province in late-March 2018. Fires usually flare up around the time that the winter snow cover melts. 53)

- The fires were initially quite small. Most of them were probably lit by people, mainly to burn dried grasses and old crop debris from fields. People in the area routinely light fires in the spring to fertilize the soil, maintain pasturelands, and prevent forest encroachment.

- Many of the fires near the Amur and Zeya rivers spread rapidly over the following week. By April, several were raging out of control—in some cases burning through forests. Dahurian larch dominates forests in Amur, though deciduous trees such as birch and aspen are also common.

- Hundreds of firefighters are working in the region, according to news reports. However, the fires are proving difficult to control and have spread about 20,000 hectares (80 square miles) per day. On April 5, authorities reported extinguishing 15 fires, but 23 new fires emerged on the same day.

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Figure 54: VIIRS on the Suomi NPP satellite captured this natural-color image of smoke streaming from several fires on April 4, 2018. Recently charred areas appear black. Rivers, still ice-covered, are white (image credit: NASA Earth Observatory, images by Jeff Schmaltz, LANCE/EOSDIS Rapid Response. Story by Adam Voiland)

• March 27, 2018: Sandwiched between Lithuania and Poland, Kaliningrad is a small piece of Russia—about half the size of Rhode Island—on the Baltic Sea. Once claimed by Prussia, Kaliningrad was annexed by the Soviet Union during World War II and has since remained under Russian control. 54)

- As this natural-color satellite image shows, the borders of Kaliningrad reveal themselves in an unexpected way—fire activity. The VIIRS (Visible Infrared Imaging Radiometer Suite) instrument on the Suomi NPP satellite acquired this natural-color image(Figure 55) on March 18, 2018. In the image of Figure 56, areas with red outlines show where the thermal band on VIIRS detected warm surface temperatures associated with fires. This image has been darkened to make the hot spots more visible. Use the image comparison to see the differences.

- This pattern—with many more fires burning in Kaliningrad than in neighboring Poland, Lithuania, and Belarus—is common in the spring, usually in March through mid-May. There are several reasons for the disparity, explained Alexander Prishchepov, a University of Copenhagen geographer who studies this region. “While intentionally lighting fires is illegal in all of these countries, enforcement of the law is much weaker in Russia,” he said. “Also important is that Kaliningrad farmers abandoned fields at a much higher rate than their neighbors after the Soviet Union collapsed.”

- Using Landsat satellite imagery collected over decades, Prishchepov and colleagues calculated that about half of Kaliningrad’s fields were abandoned after 1991. In contrast, adjacent counties in Poland and Lithuania had abandonment rates of less than 20 percent.

- When farmland gets abandoned in temperate Europe, it turns into grassy meadows and, eventually, forest. In Kaliningrad, fields that were once used to grow cereal, fodder crops, and vegetables in large collective farms are now used less intensively as pastureland or hay fields. Many owners of grasslands find that burning the prior year’s growth is a cheap and easy way to clear away old grass, fertilize the soil, and prevent forests from encroaching.

- However, it is unlikely that all of these fires are related to farming or the management of grasslands. By reviewing satellite data of fire locations over the years, Prishchepov and his colleagues have noticed that fires regularly burn quite close to towns, roads, and airports, suggesting that some of these fires could be ignited by stray sparks from cigarettes and vehicles.

- This is not the only burning season in Kaliningrad. A second burning season usually flares up in July and continues through October. During the fall burning period, most of the fires are started by farmers trying to get rid of crop debris left over after harvest, particularly straw.

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Figure 55: VIIRS on Suomi NPP acquired this natural-color image on March 18, 2018 (image credit: NASA Earth Observatory images by Jeff Schmaltz, using VIIRS data from LANCE/EOSDIS Rapid Response , Story by Adam Voiland)

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Figure 56: In this darkened image, the VIIRS thermal band detected warm surface temperatures associated with fires [image credit: NASA Earth Observatory, image by Jeff Schmaltz, using VIIRS data from LANCE/EOSDIS Rapid Response. Story by Adam Voiland, with information from Jessica McCarty (Miami University), Alexander Prishchepov (University of Copenhagen), and Svetlana Turubanova (University of Maryland)]

• March 1, 2018: Every January through March, vast numbers of small fires spring up across the countryside in Southeast Asia. Those months usually bring cool, dry weather—perfect conditions for burning. 55)

- VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite captured data (Figure 57) showing the locations of hundreds of fires burning in Cambodia, Vietnam, Thailand, Laos, and Myanmar (Burma) on February 3, 2018. Each red dot on the map depicts one fire detection from the VIIRS 750-meter active fire data product. (Note that there is also a 375-meter active fire data product that detects more fires, but the 750-meter product is the basis for this useful mapping tool.)

- On that day, there were significantly more fires in Cambodia than in neighboring countries. VIIRS detected 1,868 hot spots in Cambodia, 185 in Laos, 77 in Myanmar, 217 in Thailand, and 114 in Vietnam. The large number of fires in Cambodia were the most VIIRS has observed on a single day in 2018. The pattern is consistent with recent years: As depicted in the map of Figure 59, the instrument has detected four-to-five times as many fires in northern Cambodia as it did in Vietnam and Thailand between August 2016 and February 2018. Northern Laos also had a relatively high number of fires.

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Figure 57: On 3 Feb. 2018, the VIIRS instrument acquired this image of Southeast Asia showing the locations of hundreds of fires burning in Cambodia, Vietnam, Thailand, Laos, and Myanmar (image credit: NASA Earth Observatory, images by Joshua Stevens, using fire data from the VIIRS Active Fire team, story by Adam Voiland)

- People light fires in Southeast Asia for several reasons. In some forested areas, small-scale subsistence farmers practice swidden agriculture (also called slash-and-burn). The technique involves cutting down trees and shrubs, letting the wood dry out for a few months, and then burning it to clear fields. Hunters sometimes start fires to drive reclusive animals into view. Likewise, people collecting mushrooms sometimes burn the forest floor to make it easier to forage. Loggers use fire to clear roads and to clear the land after harvesting the most desirable species. In non-forested areas, farmers set fires to dispose of plant debris after harvesting rice, wheat, and other crops. Discarded cigarettes, sparks from vehicles, and problems with electrical systems also spark fires.

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Figure 58: Number of fire detections in Cambodia during the burning seasons- acquired between February 2014 and February 2018 (image credit: NASA Earth Observatory)

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Figure 59: VIIRS has detected four-to-five times as many fires in northern Cambodia as it did in Vietnam and Thailand between August 2016 and February 2018 (acquired February 21, 2018). Northern Laos also had a relatively high number of fires (image credit: NASA Earth Observatory, images by Joshua Stevens, using fire data from the VIIRS Active Fire team, story by Adam Voiland)

• February 9, 2018: NOAA/NASA's Suomi NPP satellite captured this image of the Korean Peninsula on February 8, 2018 (Figure 60), one day before the opening ceremony of the 2018 Winter Olympics in Pyeongchang, South Korea. Despite recent cold temperatures, there is relatively little snow over the country's more mountainous terrain, including the Taebaek Mountains where this year's games will be held. This imagery shows snow cover in the southwestern corner of the country (bright white areas near the coast), while areas near Pyeongchang are only lightly snow covered. 56)

- Located 700 m above sea level and exposed to frigid northerly winds out of Siberia during winter, the Pyeongchang region is more than cold enough for snow. Climate data from the Korean Meteorological Administration show average daily high temperatures in Pyeongchang at this time of year are just below freezing, making the area conducive to artificial snow at game venues if needed.

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Figure 60: VIIRS (Visible Infrared Imaging Radiometer Suite) on Suomi NPP captured this image on 8 Feb. 2018. Although true-color images like this one appear to be photographs of the Earth, they are actually created by combining data from three different color channels on the satellite's VIIRS instrument. These channels are sensitive to the red, green and blue (or RGB) wavelengths of light, and are blended into a single composite image (image credit: NOAA/NESDIS)

• January 6, 2018: On December 28, 2017, VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite (Figure 61) and the MODIS (Moderate Resolution Imaging Spectroradiometer) on the Aqua satellite (Figure 62) acquired the data for these natural-color images. Swirls of milky blue and green reveal the presence of massive numbers of phytoplankton in the South Atlantic Ocean near the Falkland Islands. The dense blooms stretched hundreds of kilometers. The puffs of white in each image are thin clouds. 57)

- Phytoplankton are microscopic, plant-like marine organisms that use chlorophyll to harness sunlight for energy in much the same way that land-based plants do. When conditions are right, these tiny floating organisms can multiply exponentially and spread across hundreds of square kilometers of the ocean surface.

- Phytoplankton form the center of the marine food web, serving as the primary food source for zooplankton, shellfish, fish, and larger marine creatures that consume them both. They are also critical to the global carbon cycle, as they absorb carbon dioxide from the atmosphere and turn it into carbohydrates. When the phytoplankton (or the animals that eat them) die, some of their remains sink to the ocean floor, transporting carbon to the bottom of the ocean. Finally, phytoplankton are key producers of the oxygen that makes the planet livable for humans and other creatures.

- Bloom conditions are often just right near the east coast of South America and the Falklands in southern spring and winter. The waters are fueled by abundant nutrients carried on the Malvinas Current. Spun off of the Circumpolar Current of the Southern Ocean, the Malvinas flows north and east along the coast. The waters are enriched by iron and other nutrients from Antarctica and Patagonia, and they are made even richer by the interaction of ocean currents along the shelfbreak front, where the continental shelf slopes down to the deep ocean abyssal plain.

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Figure 61: The VIIRS instrument on Suomi NPP acquired this natural color image of phytoplankton near the Falkland Islands on 28 Dec. 2017 (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS data from the Suomi NPP satellite, story by Mike Carlowicz)

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Figure 62: The MODIS instrument on NASA's Aqua satellite acquired this natural color image of phytoplankton near the Falkland Islands on 28 Dec. 2017 (image credit: NASA Earth Observatory, image by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response, story by Mike Carlowicz)

• December 27, 2017: Since 2011, the VIIRS (Visible Infrared Imaging Radiometer Suite) sensor on the Suomi NPP satellite has been collecting data on the brightness of lights—natural and manmade—that shine around the Earth at night. 58)

- Suomi NPP’s orbit allows VIIRS to collect new night light data for almost all of the Earth every night. This means the sensor does much more than generate pretty pictures. With each orbit, it adds to an ever-growing archive of data that is allowing scientists and geographers to track changes in artificial lights, fishing practices, economic activity, development patterns, the movement of goods and people, and many other research areas in innovative ways and on a global scale.

- The map of Figure 63 offers a few small-scale examples of the sort of changes that VIIRS can reveal. The map shows where the intensity of light decreased (orange), increased (purple), and stayed the same (white) between 2012 and 2016 in the Midwest. In order to make the map, all of the clear-sky imagery collected by VIIRS in 2012 was compiled into a composite and then compared to a composite of clear images from 2016.

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Figure 63: Detail map of VIIRS on Suomi NPP showing the change in night lights in the period 2012-2016 (image credit: NASA Earth Observatory, images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA GSFC. Story by Adam Voiland)

- The marked increase in light along Interstate 90 between Chicago and Rockford, as well as the increase in light around the town of Coldwater, Michigan, are two of the more noticeable features. The new light along the highway is associated with a multi-year infrastructure project to widen the road. In 2013 and 2014, the western portion of this stretch of I-90 was expanded from two to four lanes; the eastern portion went from six to eight lanes between 2014 and 2016.

- In Coldwater, Michigan, the increase in light relates to the recent construction of greenhouses that are used to raise vegetables using hydroponic growing techniques. Despite Michigan’s dark and chilly winters, the high-tech greenhouses are equipped with powerful grow lights that are often lit at night, making it possible to raise tomatoes and peppers 365 days a year.

- Many small, local changes in lighting like these can point to big changes in energy use, light pollution, and economic development over time. However, scientists—as well as the public—should be careful when interpreting the changes they see in qualitative maps of changing nighttime light, cautioned Miguel Román, a scientist at NASA’s Goddard Space Flight Center. There are several natural factors that can influence how much light the satellite detects, ranging from the phase of the Moon, lightning flashes, the presence or absence of snow or vegetation, and haze and cloud cover. These issues need to be fully understood when analyzing changes in light over time. Snow can be particularly problematic because its presence can amplify light signals even when skies are perfectly clear.

- “Some of the changes you see in this map have more to do with differences in snow cover than with changes to lights on the ground,” said Román. “However, along that part of I-90 and around Coldwater, the signal is quite strong. We have checked enough on the day-to-day and week-to-week light levels—not just whole years of data averaged together, as this map shows—that I am confident the increases are real in those two places.”

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Figure 64: The time-series chart above provides a more complete look at how the intensity of the light VIIRS detected along I-90 changed between 2012 and 2016. The uncorrected values observed by the satellite are shown in light purple. In the corrected data, shown in dark purple, algorithms developed by Román and his colleagues have filtered out changes caused by moonlight, snow, and other natural factors as much as possible (image credit: NASA Earth Observatory, images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA GSFC. Story by Adam Voiland)

- Notice that the corrected data shows a sizable—roughly tenfold—increase in light in the beginning of 2015, a clear sign that new lighting associated with the highway project came online at that time. The small peaks and valleys in the uncorrected data are associated with changes in moonlight. The steeper peaks and valleys are caused by snow amplifying the light signal. The amplification can be significant. Note that light levels went up roughly 30-fold in 2015 in the uncorrected data, but that roughly two-thirds of the increase was due to the signal being amplified by snow, explained Román.

- As time passes and more satellite data accumulates, expect to see scientists and geographers digging deeply into VIIRS data. For the past few decades, researchers have been mining an earlier generation of night light data acquired by the OLS (Operational Linescan System), which operated on weather satellites managed by the U.S. Department of Defense. “Since VIIRS is about ten to fifteen times better than the OLS at resolving the relatively dim lights of human settlements, I expect there will be even stronger interest in doing time-series analysis for VIIRS,” said Román. “It’s an exciting time to be doing this type of research.”

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Figure 65: Context image of the Great Lakes region of VIIRS on Suomi NPP showing the change in night lights in the period 2012-2016 (image credit: NASA Earth Observatory, images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA GSFC. Story by Adam Voiland)

• December 6, 2017: Tropical Storm Ockhi brought drenching rain to the west coast of India in early December 2017, while also stirring up dust plumes and disturbing stagnant, smoggy air in the interior. 59)

- On 4 Dec. 2017, VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite acquired the data for a natural-color image (Figure 66) of the tropical cyclone approaching India. The diffuse center of the storm was expected to make landfall near Mumbai and Gujarat state on December 5. Schools and colleges were shut down for the day as a precautionary measure.

- Note the smog and haze to the north and east of the storm in the December 4 image—remnants of a persistent air pollution event in the northern reaches of India. The strong winds and atmospheric circulation of Ockhi could clear that air over the next few days; rainfall also could wash many of the aerosol particles out of the air.

- To the north and west in the image, streams of airborne dust and sand blew out over the Arabian Sea from Pakistan and Iran. The plumes are a visible manifestation of strong northerly and northeasterly winds associated with the turbulent weather in the region. The outer bands of Ockhi stretched far to the north, and the system likely strengthened the pressure gradient between the cyclone and a high-pressure system to the northwest, intensifying surface winds until they picked up dust.

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Figure :66 VIIRS image of Tropical Storm Ockhi, acquired on 4 Dec. 2017 [image credit: NASA Earth Observatory, image by Jesse Allen, using VIIRS data from the Suomi NPP. Story by Mike Carlowicz, with image interpretation from Andy Ackerman (NASA GISS), Hiren Jethva (NASA/GSFC) and Steve Lang (NASA/GSFC)].

- On 5 December 2017, MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Aqua satellite acquired the second image, a natural-color view of Ockhi as the storm neared landfall. At the time of the image, sustained winds were estimated to be 45 knots (80 km/hr).

- Ockhi ( meaning “eye” in the Bengali language) is the strongest cyclone to develop in the Arabian Sea since Megh in 2015. It formed near southern India and Sri Lanka on November 30, 2017, moved out over the Arabian Sea, intensified to category 3 strength on December 2–3, but then weakened quickly as it moved north and closer to land.

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Figure 67: MODIS image of Cyclone Ockhi, acquired on 5 Dec. 2017 (image credit: NASA Earth Observatory)

• November 29, 2017: Since August 2017, residents of the Indonesian island of Bali have been living with a heightened sense of the uncertainty that comes with living near a volcano. Mount Agung has been rumbling with increasing unrest for more than three months. Activity ramped up with a small ash eruption on November 21, 2017, followed by an explosive phreatic eruption on November 25. 60)

- Clouds have so far prevented satellites from capturing visible images of the volcanic plume, but that does not mean the eruption has gone unobserved. Even on a cloudy day, some satellites excel at detecting components in the atmosphere that are invisible to human eyes, such as the sulfur dioxide (SO2) in a volcano’s plume. The gas can affect both human health and climate (Figures 68 and 69).

- Simon Carn, a volcanologist at Michigan Tech, noted that the westward motion of the plume is due to the pull of Tropical Cyclone Cempaka south of Java.

- Also notice that by November 28, the SO2 plume directly over the volcano appears to have decreased. “It is definitely normal that it should fluctuate a bit,” said Janine Krippner, a volcanologist at the University of Pittsburgh. “But the volcano is definitely not winding down at this point.” She also notes that the concern now is that there is a clear pathway through which lava can travel to the surface. An “open system” like this one led to deadly lava flows during the volcano’s last major eruption in 1963.

- According to a report by the Jarkata Globe, about 100,000 people live on the volcano’s slopes but less than half have evacuated. The eruption has also led to airport closures and the cancellation of hundreds of flights.

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Figure 68: SO2 concentrations detected over Mount Agung on 27 November with OMPS on Suomi NPP (image credit: NASA Earth Observatory, image by Joshua Stevens, using OMPS data from the Goddard Earth Sciences Data and Information Services Center (GES DISC). Story by Kathryn Hansen)

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Figure 69: SO2 concentrations detected over Mount Agung on 28 November with OMPS on Suomi NPP (image credit: NASA Earth Observatory, image by Joshua Stevens, using OMPS data from the Goddard Earth Sciences Data and Information Services Center (GES DISC). Story by Kathryn Hansen)

• On October 17, 2017, the VIIRS (Visible Infrared Imaging Radiometer Suite) instrument on the Suomi NPP satellite captured this image (Figure 70) of an unusual cloud pattern off the coast of southern Australia. 61)

- Clouds appear to be streaming out from a cold front, indicated by the dark blue line on a weather map published that day by Australia’s BOM (Bureau of Meteorology). But according to Paul Lainio, BOM meteorologist, that’s not actually what’s happening.

- Instead, the pattern is caused by a phenomenon in the atmosphere called “gravity waves.” Similar to a boat’s wake, which forms as water is pushed upward by the boat and pulled downward again by gravity, these clouds are formed by the rise and fall of air columns. As the wave moves along the cloud band, the wave peaks appear cloudy and the troughs appear cloud-free. In this case, the gravity waves developed as a result of instability on the flank of a strong jet stream moving ahead of the cold front.

- “This type of effect is relatively unusual since it requires a strong anticyclonic-curved jet that develops gravity waves of sufficient magnitude,” Lainio said. “The gravity waves are the atmosphere’s way of restoring balance, and they usually don’t last for lengthy periods.”

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Figure 70: The VIIRS instrument captured this unusual cloud pattern on 17 Oct. 2017 (image credit: NASA Earth Observatory, image by Joshua Stevens using VIIRS data from LANCE/EOSDIS Rapid Response. Story by Kathryn Hansen)

• September 25, 2017: Hurricane Maria was analyzed in visible and infrared light as NASA-NOAA's Suomi NPP passed overhead over two days. NASA's GPM satellite also provided a look at Maria's rainfall rates. 62)

- On Sept. 23 at 8:12 a.m. EDT (12:12 UTC) the GPM (Global Precipitation Measurement) mission core observatory estimated of hourly rainfall in multiple intense rainfall bands of thunderstorms around Maria's western side. Rain was found falling at a rate of over 137 mm/hour and some thunderstorm tops in these rain bands were found to reach heights above 15.7 km. GPM is managed by NASA and JAXA (Japan Aerospace Exploration Agency).

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Figure 71: The GPM core observatory estimated of hourly rainfall of Hurricane Maria. Rain was found falling at a rate of over 137 mm/hour (image credit: NASA/JAXA, Hal Pierce)

- On Sept. 24 at 1:54 p.m. EDT (17:54 UTC), the VIIRS (Visible Infrared Imaging Radiometer Suite) instrument aboard NASA-NOAA's Suomi NPP satellite captured a visible light image of Hurricane Maria that showed the eye had become cloud filled. Maria was located northeast of Bahamas and far off the Florida east coast (Figure 72).

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Figure 72: The VIIRS instrument provided this image of Hurricane Maria when it was northeast of Bahamas and east of the Florida east coast (image credit: NOAA/NASA Goddard Rapid Response Team)

- On Sept. 25 at 2:12 a.m. EDT (06:12 UTC) the VIIRS instrument aboard NASA-NOAA's Suomi NPP satellite provided tan infrared image of Hurricane Maria (Figure 73). The infrared image provided forecasters with temperature data that showed where the strongest storms were located within the hurricane. Coldest clouds tops and strongest storms were in the southeastern quadrant where temperatures were as cold as or colder than minus minus 62.2º C. NASA research has shown that storms with cloud top temperatures that cold can produce heavy rainfall.

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Figure 73: The VIIRS instrument aboard NASA-NOAA's Suomi NPP satellite provided this infrared image of Hurricane Maria. Coldest cloud tops (red) and strongest storms were in the southeastern quadrant (image credit: NOAA/NASA Goddard Rapid Response Team)

• September 9, 2017: Meteorologists struggled to find the right words to describe the situation as a line of three hurricanes—two of them major and all of them threatening land—brewed in the Atlantic basin in September 2017. 63)

- Forecasters were most concerned about Irma, which was on track to make landfall in densely populated South Florida on September 10 as a large category 4 storm. Meanwhile, category 2 Hurricane Katia was headed for Mexico, where it was expected to make landfall on September 9. And just days after Irma devastated the Leeward Islands, the chain of small Caribbean islands braced for another blow—this time from category 4 Hurricane Jose.

- The VIIRS instrument on the Suomi NPP satellite captured the data for a mosaic of Katia, Irma, and Jose as they appeared in the early hours of September 8, 2017. The images were acquired by the VIIRS “day-night band,” which detects light signals in a range of wavelengths from green to near-infrared, and uses filtering techniques to observe signals such as city lights, auroras, wildfires, and reflected moonlight. In this case, the clouds were lit by the nearly full Moon. The image is a composite, showing cloud imagery combined with data on city lights.

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Figure 74: Suomi NPP image of Hurricanes Katia, Irma and Jose, captured on September 8, 2017 (image credit: NASA Earth Observatory,images by Joshua Stevens and Jesse Allen, using VIIRS day-night band data from the Suomi NPP, story by Adam Voiland)

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Figure 75: MODIS on NASA's Terra satellite acquired a natural-color image of Irma at 16:00 UTC on September 8, 2017 (image credit: NASA Earth Observatory,images by Joshua Stevens and Jesse Allen, using MODIS data from LANCE (Land Atmosphere Near real-time Capability for EOS), story by Adam Voiland)

• On September 6, 2017, Hurricane Irma slammed into the Leeward Islands on its way toward Puerto Rico, Cuba, and the U.S. mainland. As the category 5 storm approaches the Bahamas and Florida in the coming days, it will be passing over waters that are warmer than 30 degrees Celsius (86 degrees Fahrenheit)—hot enough to sustain a category 5 storm. Warm oceans, along with low wind shear, are two key ingredients that fuel and sustain hurricanes. 64)

- The map of Figure 76 shows sea surface temperatures in the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico on September 5, 2017. The data were compiled by NOAA's CRWP (Coral Reef Watch Program), which blends observations from the Suomi NPP, MTSAT, Meteosat, and GOES satellites and computer models. The mid-point of the color scale is 27.8°C, a threshold that scientists generally believe to be warm enough to fuel a hurricane. The yellow-to-red line on the map represents Irma’s track from September 3–6.

- By definition, category 5 storms deliver maximum sustained winds of at least 252 km/ hour. When it hit the Leeward Islands, Irma’s winds surpassed 295 km/ hour, making it the strongest storm to ever hit the islands and one of the strongest storms ever measured in the Atlantic basin.

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Figure 76: Sea surface temperatures in the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico on September 5, 2017. NOAA compiled the data from the Suomi NPP, MTSAT, Meteosat, and GOES satellites and computer models (image credit: NOAA, NASA Earth Observatory image by Joshua Stevens and Jesse Allen)

• September 6, 2017: With dozens of wildfires burning across the western United States and Canada, many North Americans have had the acrid taste of smoke in their mouths during the past few weeks. On September 5, 2017, the NIFC (National Interagency Fire Center) reported more than 80 large fires burning in nine western U.S. states. People living in large stretches of northern California, Oregon, Washington, and Idaho have been breathing what the U.S. government’s Air Now website rated as “hazardous” air. 65)

- The natural-color mosaic of Figure 77 was made from several scenes acquired on September 4, 2017, by the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi National Polar-orbiting Partnership (Suomi-NPP) satellite. The OMPS (Ozone Mapper Profiler Suite ) on Suomi NPP also collected data on airborne aerosols as they were swept by winds from west to east across the continental United States (second image).

- The OMPS map depicts relative aerosol concentrations, with lower concentrations appearing in yellow and higher concentrations appearing in dark orange-brown. Note that the sensor detects aerosols in high-altitude plumes more readily than lower plumes, so this map does not reflect air quality conditions at “nose height.” Rather it shows where large plumes of smoke were lofted several kilometers up into the atmosphere.

- On September 5, roughly 7.8 million acres had burned in the United States since the beginning of 2017, according to NIFC. “While it is unlikely that this season will be record-breaking for modern fire record keeping in the western United States, it is above normal relative to the last decade—which has seen abundant fire activity,” said John Abatzoglou, a fire researcher at the University of Idaho. Unusually warm and dry conditions across a broad swath of the West has fueled the active fire season, noted Abatzoglou. A wet winter in some parts of the West also contributed by triggering the growth of more grass in the spring—grass that turns into fuel for fires in the summer.

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Figure 77: VIIRS natural color image, acquired on Sept. 4, 2017 (image credit: NASA Earth Observatory, images by Joshua Stevens and Jesse Allen, using Suomi NPP VIIRS data, Story by Adam Voiland)

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Figure 78: The OMPS map depicts relative aerosol concentrations, with lower concentrations appearing in yellow and higher concentrations appearing in dark orange-brown (image credit: NASA Earth Observatory, images by Joshua Stevens and Jesse Allen, using Suomi NPP OMPS data provided courtesy of Colin Seftor (SSAI), Story by Adam Voiland)

• September 3, 2017: Hurricane Harvey changed the landscape of southern Texas and the lives of millions of people. The storm also changed the surface profile of the Gulf of Mexico, though those effects are likely to be short-lived. 66)

- When Harvey crossed the Yucatán Peninsula into the Gulf of Mexico on August 22–23, 2017, the tropical depression moved into waters that were 1.5 to 4º Celsius warmer than the long-term regional average for sea surface temperatures. Hurricanes feed off of warm ocean temperatures, like a fire relies on a steady oxygen supply to keep burning. “So this deep, warm pool of water helped provide additional fuel for Harvey to intensify,” said Dalia Kirschbaum, a scientist and natural hazards specialist at NASA/GSFC (Goddard Space Flight Center).

- Once in the Gulf, Harvey grew rapidly and sped toward the Texas coast as a category 4 hurricane — then lingered for five days as a potent tropical storm. In the process, the storm dropped unprecedented amounts of rainwater on Houston and southern Texas while churning up the Gulf of Mexico.

- The maps of Figure 79 show sea surface temperatures in the western Gulf of Mexico on August 23 and August 30, 2017, as well as the storm track for Harvey. The pair of maps of Figure 80 show sea surface temperature anomalies; that is, how much the surface layer was above or below the long-term average temperature for this time of year. The data for all of the maps were compiled by Coral Reef Watch, which blends observations from the Suomi NPP, MTSAT, Meteosat, and GOES satellites with computer models.

- All of the fresh rainwater and the ocean mixing from the storm combined to dramatically alter the surface waters of the Gulf. Cooling naturally as it rose through the atmosphere, the water that fell back onto the sea as rain likely would have been cooler than the surface waters. At the same time, the winds and waves of the storm worked to disperse warm surface water and to bring up cooler water from the ocean depths.

- In theory, the cooler water now near the surface of the northern Gulf of Mexico should make it less likely for a new storm to develop or intensify there in the coming weeks. However, the waters of the Gulf are not exactly cool. Scientists generally agree that SSTs (Sea Surface Temperatures) should be above 27.8°C to promote the development and intensification of hurricanes. (There are some exceptions.) So even some of the light blues on our sea surface temperature maps are still warm enough for storms.

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Figure 79: Surface temperatures in the Golf western Gulf of Mexico, acquired on August 23 and August 30, 2017, as well as the storm track for Harvey. The data were compiled by Coral Reef Watch, which blends observations from the Suomi NPP, MTSAT, Meteosat, and GOES satellites with computer models (image credit: NASA Earth Observatory, images by Joshua Stevens, using data from Coral Reef Watch and Unisys, Story by Mike Carlowicz)

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Figure 80: Western Golf of Mexico sea surface temperature anomalies - difference from the long-term average temperature for this time of the year. The observations were in the time frame August 23 and August 30, 2017. The data were compiled by Coral Reef Watch, which blends observations from the Suomi NPP, MTSAT, Meteosat, and GOES satellites with computer models (image credit: NASA Earth Observatory, images by Joshua Stevens, using data from Coral Reef Watch and Unisys, Story by Mike Carlowicz)

• July 2017: The VIIRS instrument onboard the Suomi-NPP satellite has transitioned much of the capability of the experimental MODIS (MODerate Resolution Imaging Spectroradiometer) instruments into the operational domain. VIIRS provides a continuation of global environment monitoring for Land, Ocean, Cloud, and Atmosphere. The high quality observations and derived products generated from VIIRS have been used to improve operational environmental forecast skills and enhance our understanding of climate change processes. 67)

- Since Suomi-NPP successfully launched in October 2011, NOAA STAR (Satellite Applications and Research) science teams have been focused on maintaining, development, calibration/validation, and upgrade of the VIIRS algorithms. By far, most of the Suomi-NPP VIIRS sensor and environmental data products have been fully validated and characterized through rigorous cal/val review process. The validated science algorithms are now used for reprocessing of the entire Suomi-NPP mission lifetime of the VIIRS data product records.

- In the past and to some extent currently, the scientific community utilizing satellite derived products for land, ocean, and atmospheric applications have relied on the legacy NOAA/POES (Polar Orbiting Environmental Satellites), MetOp satellites [e.g. AVHRR (Advanced Very High Resolution Radiometer)], and the experimental MODIS from the EOS (Earth Observing System) Aqua and Terra satellites.

- The VIIRS instrument offers very similar bands as like the MODIS with similar radiometric accuracy. In addition, the instrument offers many more spectral bands with a better spatial resolution and reduced variation over the scan. Further, the availability of the DNB (Day Night Band) offers a wide variety of applications and makes the VIIRS JPSS products more vital for long-term continuity with greater operational utility.

- Suomi-NPP VIIRS produces more than 20 EDR (Environmental Data Record) products and these products are being used operationally by the weather forecast offices nationwide and many other national/international agencies worldwide. JPSS-1 and subsequent series of satellites will continue to produce these base-line products from VIIRS and new and additional products as a direct result of upgrades and science improvements. Operational users receive JPSS-1 VIIRS SDR/EDR data products from the NOAA PDA (Product Distribution and Access) interface. Suomi-NPP/JPSS VIIRS data products are also accessible to public and non-operational users worldwide through the NOAA CLASS (Comprehensive Large Array-data Stewardship System). The direct readout users receive live Suomi-NPP/JPSS VIIRS data using direct downlink capabilities and the CSPP (Community Satellite Processing Package) allows the creation of many SDR and imagery products in real-time.

- In summary, the VIIRS products currently available from the Suomi-NPP have all reached validated maturity. The scientific maturity of these products is well documented and the Cal/Val artifacts are available on the JSTAR(JPSS Satellite Applications and Research) website. These products are easily accessible via NOAA operations, direct readout, and NOAA CLASS. Replacement and upgrade of current Suomi-NPP algorithms with NOAA enterprise algorithms and reprocessing of Suomi-NPP mission-long data sets are at pace to generate consistent, high-quality products as well as blended products. Plans are in progress to provide calibrated radiances as well as other JPSS EDR products from all of the JPSS instruments through Direct Broadcast services in support of many real time regional applications. VIIRS products from the Suomi-NPP, and continued through a series of satellite launches (J1, J2, and so on until the year 2030) provide continued support for land, ocean and atmospheric applications. Leveraging the Suomi-NPP Cal/Val experience, the Cal/Val activities for JPSS-1 are expected to be much more accelerated than those for Suomi-NPP, and JPSS-1 data products will be provided to decision makers/users with a much improved latency.

Table 5: Overview of the VIIRS data product performance - continuing with the JPSS (Joint Polar Satellite System) missions 67)

• On June 17,2017, lightning reportedly ignited a deadly wildfire that spread across the mountainous areas of Pedrógão Grande—a municipality in central Portugal located about 160 km northeast of Lisbon. The MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra satellite captured a daytime image of smoke billowing northward from areas of active burning on June 18. The following night the blaze continued to burn so bright that it was visible from space. 68)

- VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite captured a nighttime image of the fire at 2:48 a.m. local time (01:48 UTC on June 19, 2017, Figure 81). For comparison, the second image of Figure 82 shows the same area in the predawn hours of June 16. Turn on the image-comparison tool to see the fires brighten the rural landscape between the urban areas. Note that some differences in brightness and sharpness are due to the presence of more cloud cover in the June 19 image. The fire was imaged by a special “day-night band” that detects light in a range of wavelengths from green to near-infrared and uses light intensification to detect dim signals.

- Fires across Portugal’s forested landscape during the warm, dry summer months are not uncommon. In 2016, hundreds of fires raged on the mainland and also on the Portuguese island of Madeira. The high death toll associated with this week’s fire, however, led The New York Times and other media to report it as “Portugal’s worst forest fire in more than half a century.”

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Figure 81: VIIRS nighttime image of the fires in Portugal acquired on June 19, 2017 (image credit: NASA Earth Observatory, image by Jesse Allen, using VIIRS day-night band data from the Suomi NPP, story by Kathryn Hansen)

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Figure 82: VIIRS image of the same region in Portugal acquired in the predawn hours on June 16, 2017 (image credit: NASA Earth Observatory, image by Jesse Allen, using VIIRS day-night band data from the Suomi NPP, story by Kathryn Hansen)

• May 16, 2017: Image comparison: Unlike most satellite imagery and data, views of Earth at night tell a distinctly human story. From fires to fishing boats to urban neon, lights show where people have made their homes, set up their industries, and laid down their roads. The lack of light usually reflects rural or uninhabited areas, though sometimes it means there is not enough electricity to keep lights on through the night. 69)

- Changing patterns of light over time also tell us something. The images above show differences in nighttime lighting between 2012 and 2016 in Syria and Iraq, among several Middle Eastern countries. Such images interest demographers, engineers, and social scientists because they can indicate economic development or the lack of it. Some changes reflect increases or decreases in electric power generation or in the steadiness of the supply. Even areas that switch to LEDs or other energy efficient lights can show up over time.

- Night light images also have value for international relief and humanitarian organizations, which can use this data to pinpoint areas in need. NASA makes its Earth observations freely and openly available (often via the Web) to those seeking solutions to important global issues. Several current applied sciences efforts within NASA are aimed at making satellite data more readily accessible for disaster response and the delivery of aid.

- Each image of Figures 83 and 84 is drawn from a global composite that was made by selecting the best cloud-free nights in each month over each land mass on Earth. The data come from the VIIRS (Visible Infrared Imaging Radiometer Suite) on the NASA-NOAA Suomi NPP satellite. VIIRS includes a special “day/night band,” a low-light sensor that makes quantitative measurements of light emissions and reflections, allowing researchers to distinguish the intensity, types, and sources of night lights and to observe how they change over several years.

- A research team led by Miguel Román of NASA’s Goddard Space Flight Center recently released new global maps of Earth at night from 2012 and 2016. Román and colleagues are collaborating with institutions such as the U.S. Federal Emergency Management Agency and the United Nations to enable near-real-time applications of such data, in addition to fundamental research.

- In the images of Figures 83 and 84, the changes are most dramatic around Aleppo, but also extend through western Syria to Damascus. Over the four years, lighting increased in areas north of the Syrian border in Turkey and to the west in Lebanon. According to a 2015 report from the Voice of America, as much as 80 percent of the lights have gone out in Syria over the past few years.

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Figure 83: VIIRS image on Suomi NPP of the Syria and Irak region acquired in 2012 (image credit: NASA Earth Observatory, images by Joshua Stevens, story by Michael Carlowicz)

- In Iraq, some northern sections near Mosul saw a decrease in light over the years, while areas around Baghdad, Irbil, and Kirkuk saw increases. Note, too, the change in electric light patterns along the Tigris and Euphrates river basins.

- International agencies such as the United Nations Institute for Training and Research Operational Satellite Applications Program (UNITAR-UNOSAT) have used such imagery in the past few years “to track fast-moving conflicts and to update our UN colleagues on where the front lines might be,” said Lars Bromley, a remote sensing specialist with the agency. UNOSAT works to “improve the integration of satellite imagery and geospatial data in supporting global UN operations and activities in the areas of disaster response, humanitarian support, human security, and human rights.” Nighttime imagery helps relief and peacekeeping groups identify areas that are most in need of aid and support.

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Figure 84: VIIRS image on Suomi NPP of the Syria and Irak region acquired in 2016 (image credit: NASA Earth Observatory, images by Joshua Stevens, story by Michael Carlowicz)

• April 12, 2017: NASA scientists are releasing new global maps of Earth at night, providing the clearest yet composite view of the patterns of human settlement across our planet. This composite image, one of three new full-hemisphere views, provides a view of the Americas at night. The clouds and sun glint — added here for aesthetic effect — are derived from MODIS instrument land surface and cloud cover products. 70)

- In the years since the 2011 launch of the NASA-NOAA Suomi- NPP (National Polar-orbiting Partnership) satellite, a research team led by Earth scientist Miguel Román of NASA/GSFC (Goddard Space Flight Center) has been analyzing night lights data and developing new software and algorithms to make night lights imagery clearer, more accurate and readily available. They are now on the verge of providing daily, high-definition views of Earth at night, and are targeting the release of such data to the science community later this year.

- Today they are releasing a new global composite map of night lights as observed in 2016, as well as a revised version of the 2012 map. The NASA group has examined the different ways that light is radiated, scattered and reflected by land, atmospheric and ocean surfaces. The principal challenge in nighttime satellite imaging is accounting for the phases of the moon, which constantly varies the amount of light shining on Earth, though in predictable ways. Likewise, seasonal vegetation, clouds, aerosols, snow and ice cover, and even faint atmospheric emissions (such as airglow and auroras) change the way light is observed in different parts of the world.

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Figure 85: Earth at Night map (image credit: NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NAS/GSFC) 71)

Suomi NPP observes nearly every location on Earth at roughly 13:30 and at 1:30 hrs (local time) each day, observing the planet in vertical 3000 km strips from pole to pole. VIIRS includes a special “day-night band,” a low-light sensor that can distinguish night lights with six times better spatial resolution and 250 times better resolution of lighting levels (dynamic range) than previous night-observing satellites. And because Suomi NPP is a civilian science satellite, the data are freely available to scientists within minutes to hours of acquisition.

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Figure 86: Composite image of Mid-Atlantic and Northeastern U.S. (Boston-Washington corridor) at night, 2016 (image credit: NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA/GSFC)

• February 22, 2017: Yet another series of atmospheric rivers has drenched California and the American West in a stunning turnaround from five years of drought. Many parts of California have received nearly twice as much rain as normally falls in the first five months of a water year, which began on October 1. 72)

- Flood and landslide warnings are in effect in many counties, particularly in the Sacramento Valley, which is crossed by several rivers and sits downstream from several large reservoirs and dams. According to news reports, more than two dozen mud/debris flows have been reported across California, and at least 30 major roads have been flooded at various times in the past week. Spillways have been opened at the Anderson, Oroville, and Monticello dams, among others.

- The map of Figure 88 shows satellite-based measurements of rain, snow, and other wintry precipitation as it has accumulated over California, Nevada, Utah, and Arizona this year. Specifically, it adds the daily precipitation totals from December 31, 2016, to the evening of February 20, 2017. These are remotely-sensed estimates, and local amounts can be significantly higher when measured from the ground. The brightest areas on the map depict as much as 1000 mm of precipitation.

- More than 12 cm of rain fell in parts of northern California and along the western foothills of the Sierra Nevada on February 19–20. Daily rainfall records for February 20 were doubled in San Jose (4.75 cm) and San Francisco (5.5 cm ). According to Colorado State University meteorologist Phil Klotzbach and National Weather Service sources, San Francisco has received 41.6 cm of rain since January 1, while Oakland has received 52.85 cm; the typical yearly total is 58 cm.

- During an atmospheric river event in southern California on February 17–18, new rainfall records were set in Death Valley (1.65 cm) and Santa Barbara (10.6 cm). More than 100,000 people lost power in the Los Angeles Metropolitan area on February 17 due to the storms.

- Las Vegas Valley set a new record rainfall on February 18, measuring 1.1 cm that day. Locations on the west side of the valley received double that amount. Meanwhile, in northern Nevada, Mount Rose has been buried under 12.7 m of snow this winter. The Mount Rose Highway between Reno and Lake Tahoe has been closed by an avalanche that dropped 6 m of snow on the road.

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Figure 87: VIIRS on Suomi NPP captured a natural-color image of conditions over the northeastern Pacific. Note the tight arc of clouds stretching from Hawaii to California, a visible manifestation of the atmospheric river pouring moisture into western states (image credit: NASA Earth Observatory, images by Jesse Allen and Joshua Stevens using VIIRS data)

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Figure 88: Precipitation accumulated over the western states in 2017. The data come from IMERG (Integrated Multi-Satellite Retrievals for GPM), a product of the Global Precipitation Measurement mission (image credit: NASA Earth Observatory, images by Jesse Allen and Joshua Stevens using IMERG data of GPM)

• February 14, 2017: After extreme drought and water shortages plagued California for years, a series of winter storms pushed reservoirs in the Sacramento Valley to the brim in January and February 2017. Rivers and reservoirs are swollen throughout California. VIIRS on Suomi NPP captured the image of Figure 89 on Feb. 11, 2017. 73)

- For comparison, the image of Figure 90 shows the same area on November 9, 2016, before the wet weather arrived. Large amounts of water have pooled in the Yolo Bypass, a water storage area designed to minimize flooding in Sacramento. Sediment stirred up during the flooding has turned waterways throughout northern California—including San Pablo Bay and Suisun Bay—a dark shade of brown.

- With weather stations in the northern Sierra Nevada recording remarkably high levels of precipitation for the 2016-2017 water year, reservoir levels are well above the historical average in the Sacramento Valley and elsewhere in California. As of February 11, 2017, Lake Oroville stood at 151% of the historical average. Folsom Lake was at 144%, Lake Shasta was at 138%, Don Pedro Reservoir was at 141%, and Lake McClure was at 182%.

- At the Oroville Dam, the situation became dire on February 7, 2017, when a large hole appeared in the main concrete spillway, a part of the dam managers use to release excess water in a controlled fashion. The hole limited how much water authorities could safely release through the spillway, so water levels in the reservoir continued to rise. A few days later, water began flowing over an emergency spillway that has never before been used. When the emergency spillway began showing worrisome signs of erosion on February 12, authorities ordered the evacuation of 188,000 people living downstream.

- Lake Oroville’s levels have declined since the evacuation order and the risk of a catastrophic failure has lessened. But reservoir managers remain concerned that rain showers forecast for this week could elevate reservoir water levels and stress the spillways again. As of 11 a.m. on February 13, the evacuation order remained in effect.

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Figure 89: VIIRS on Suomi NPP captured this natural-color image of sediment-filled waterways in the Sacramento Valley on February 11, 2017 (image credit: NASA Earth Observatory, image by Jesse Allen, caption by Adam Voiland)

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Figure 90: For comparison, VIIRS on Suomi NPP captured this natural-color image on Nov. 9, 2016, before the wet weather arrived (image credit: NASA Earth Observatory, image by Jesse Allen, caption by Adam Voiland)