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:

• September 26, 2019: People in coastal towns along the west coast of southern Africa watched skies turn red on September 25, 2019. Fierce wind picked up and carried huge plumes of sand and dust westward toward the Atlantic Ocean. 26)

- The South African Weather Service reported that the winds lofted enough particles into the air to produce moderate to poor visibility. Indeed, photographs from people in Alexander Bay show dark, hazy skies and streets that are barely visible. According to news reports, aircraft were unable to land at nearby airports.

- The amount of dust lofted from land in the Southern Hemisphere is negligible compared to that of the Northern Hemisphere. Africa’s Sahara Desert, for example, is one of the world’s major dust sources. Still, when winds blow over dry areas of the Southern Hemisphere, dust storms can be fierce. A similar scene unfolded in October 2018, when a thick, narrow plume streamed from the same area.

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Figure 10: The plumes were observed on 25 September 2019 at 2:25 p.m. South Africa Standard Time (12:25 Universal Time) with VIIRS on the NOAA/NASA Suomi- NPP satellite. The event covered a wide area north and south of the Orange River, which forms part of the border between Namibia and South Africa (image credit: NASA Earth Observatory image by Lauren Dauphin, using VIIRS data from NASA EOSDIS/LANCE and GIBS/Worldview, and Suomi-NPP. Story by Kathryn Hansen)

• September 13, 2019: Wherever fires are burning around the world NASA-NOAA’s Suomi-NPP satellite’s OMPS (Ozone Mapping and Profiler Suite) can track the smoke and aerosols. On Sept. 13, 2019, data from OMPS revealed aerosols and smoke from fires over both South America and North America. 27)

- Suomi-NPP’s OMPS tracks the health of the ozone layer and measures the concentration of ozone in the Earth's atmosphere and can detect aerosols. Ozone is an important molecule in the atmosphere because it partially blocks harmful ultra-violet radiation from the sun. OMPS data help scientists monitor the health of this vital protective layer.

- OMPS also can be used to measure concentrations of atmospheric aerosols from dust storms and similar events as well as sulfur dioxide (SO2) from volcanic eruptions. One aerosol-related OMPS product is a value known as the “AI (Aerosol Index). The AI value is related to both the thickness and height of the atmospheric aerosol layer. For most atmospheric events involving aerosols, the AI ranges from 0.0 to 5.0, with 5.0 indicating heavy concentrations of aerosols that could reduce visibilities and/or impact health.

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Figure 11: Fires in South America generated smoke that continues to create a long plume east into the Atlantic Ocean. Fires over western Brazil were generating aerosols at a level 2.0 on the index. Higher aerosol concentrations, as high as 4.0 were seen off the southeastern coast of Brazil as a result of the fires in the region (image credit: NASA/NOAA, Colin Seftor)

- An aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. Aerosols can be natural or anthropogenic (manmade). Examples of natural aerosols are fog, dust and geyser steam. Examples of manmade aerosols include haze (suspended particles in the lower atmosphere), particulate air pollutants and smoke.

- High aerosol concentrations not only can affect climate and reduce visibility, they also can impact breathing, reproduction, the cardiovascular system, and the central nervous system, according to the U.S. Environmental Protection Agency. Since aerosols are able to remain suspended in the atmosphere and be carried along prevailing high-altitude wind streams, they can travel great distances away from their source and their effects can linger.

- Fires in South America generated smoke that continues to create a long plume east into the Atlantic Ocean. Fires over western Brazil were generating aerosols at a level 2.0 on the index. Higher aerosol concentrations, as high as 4.0 were seen off the southeastern coast of Brazil as a result of the fires in the region.

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Figure 12: In North America, Suomi-NPP’s OMPS detected smoke and aerosols from fires over Canada’s Yukon Territories. Aerosol concentrations were very high over the Yukon fires due to a pyrocumulus event that occurred on 11 September. In the image, there is also light brown area of smoke that looks like a letter “C” on its side. The image also shows a low pressure system (the area of spiraled clouds) off the coast of western Canada (image credit: NASA/NOAA, Colin Seftor)

- In North America, Suomi-NPP’s OMPS detected smoke and aerosols from fires over Canada’s Yukon Territories. Aerosol concentrations were very high over the Yukon fires due to a pyrocumulus event that occurred on September 11.

- Pyrocumulus clouds—sometimes called “fire clouds”—are tall, cauliflower-shaped, and appear as opaque white patches hovering over darker smoke in satellite imagery. Pyrocumulus clouds are similar to cumulus clouds, but the heat that forces the air to rise (which leads to cooling and condensation of water vapor) comes from fire instead of sun-warmed ground. Under certain circumstances, pyrocumulus clouds can produce full-fledged thunderstorms, making them pyrocumulonimbus clouds.

- Scientists monitor pyrocumulus clouds closely because they can inject smoke and pollutants high into the atmosphere. As pollutants are dispersed by wind, they can affect air quality over a broad area.

- The image also contains a light brown area of smoke that looks like a letter “C” on its side and a low pressure system (the area of spiraled clouds) off the coast of western Canada.

- Both images were created at the NASA Goddard Space Flight Center in Greenbelt, Md.

• September 9, 2019: A team of engineers, scientists, and satellite operators recently restored a damaged satellite instrument that is used to measure temperature and water vapor in the Earth’s atmosphere. After the CrIS (Cross-track Infrared Sounder) instrument was damaged by radiation as it flew on the Suomi-NPP satellite, the team made a successful switch to the sensor’s electronic B-side, returning the instrument to full capability. 28)

- Meanwhile, to fill the data gap created by the event, scientists from the JPSS (Joint Polar Satellite System) fast-tracked similar data from Suomi-NPP’s cousin, the NOAA-20 satellite, to the National Weather Service (NWS).

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Figure 13: The CrIS instrument, which was damaged and then restored to full capability while on orbit, flies on the Suomi NPP (National Polar-orbiting Partnership) satellite (image credit: NASA)

- The CrIS instrument probes the sky vertically for details on temperature and water vapor — using a process is known as sounding. These observations provide important information on our planet’s atmospheric chemistry and composition, which inform weather forecast centers, environmental data records and field campaign experiments. CrIS can also quantify the distributions of trace gases in the atmosphere, such as carbon dioxide and methane.

- CrIS observes in three spectral bands within the infrared part of the spectrum: shortwave, midwave and longwave. Analysts first detected the anomaly in the midwave data on Saturday, March 23. By Monday, things weren’t looking good, said Flavio Iturbide-Sanchez, the CrIS instrument’s calibration validation lead.

- The midwave band, which includes channels sensitive to water vapor, had stopped reading properly. The next day, measurements from that band had disappeared completely.

- “Midwave is particularly focused on moisture,” said Clayton Buttles, the CrIS chief engineer for L3Harris Technologies, the instrument’s contractor. “Losing that creates a hole in the data products used to generate weather forecast predictions. Ideally, you want to combine all three bands into a comprehensive unit that allows for better forecast and prediction.”

- An algorithm called the NUCAPS (NOAA Unique Combined Atmospheric Processing System), provides the only satellite soundings available to National Weather Service’s weather forecast offices, said Bill Sjoberg, a senior systems engineer with NOAA and JPSS. NUCAPS combines infrared and microwave observations to produce atmospheric profiles of temperature and water vapor, and it relies on CrIS data. Without the CrIS soundings, forecasters would have risked losing the ability to derive an important set of measurements during afternoon hours when severe convection is most common.

- But NOAA-20, which flies 50 minutes ahead, has its own identical CrIS instrument.

- Accelerating access to NOAA-20 satellite soundings for the National Weather Service “helped reestablish the ability to track changes in severe weather conditions,” Sjoberg said.

- Meanwhile, after months of analyzing what went wrong in March, the team determined that the problem with the instrument was likely caused by radiation damage to its midwave infrared signal processor, said David Johnson, NASA’s CrIS instrument scientist. Raw data from the detectors goes through the signal processor, where the data rate gets greatly reduced in size so that it can be efficiently delivered to the ground stations.

- Fortunately, like all of the JPSS instruments and much of the spacecraft, CrIS has redundant parts. It was designed with this threat in mind. It contains a “Side 2,” a fully functional backup set of electronics, which the team hoped had not been damaged. “But we wouldn’t know without making the switch,” Iturbide-Sanchez said.

- For three months, the team studied the instrument. They ran a “reliability analysis.” They weighed the risks. They “located and verified all configuration files for Side 2,” Johnson said.

- On June 21, the team made the official decision to switch to Side 2, and three days later, they executed the switch. The turn-on process involved tuning the instrument and checking settings. But Iturbide-Sanchez knew almost immediately that the three bands were working.

- The plan was to complete the turn-on in two weeks. They did it in five days, a result of working long hours and frequent communication with ground station command. And by early July, satellite soundings had been recovered and the product was good enough to be used in weather models.

- It was very much a team effort, Iturbide-Sanchez and Johnson both said: The Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin and the Joint Center for Earth System’s Technology at the University of Maryland, Baltimore County, worked with the team during both phases, contributing to the preparation of a configuration file before the side switch, and evaluating data quality after.

- “NOAA invests in redundant systems to maximize the useful life of the instruments,” said Jim Gleason, NASA project scientist for JPSS. “This is a story of the system working as designed.”

- Making the successful switch from Side 1 to Side 2 also allows for National Weather Service products that provide early warnings for events like hurricanes, Buttles said: “We would all be worse off if we didn’t have that data.”

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Figure 14: An engineer works on the CrIS instrument for the JPSS-2 satellite, which is slated to launch in March 2022. The CrIS instrument also flies on the Suomi-NPP satellite, and was recently restored to full capability after getting damaged while on orbit (image credit: L3Harris Technologies)

• September 6, 2019: After devastating the Bahamas and grazing Florida and Georgia, Hurricane Dorian rebounded and raked the coast of South Carolina with strong winds, heavy rains, and a storm surge. Wind, falling trees, and flooding damaged power infrastructure in coastal areas of the southeast U.S. 29)

- The VIIRS sensor observed thick cloud bands circulating around Dorian’s large eye, the part of the storm with mostly calm weather and the lowest atmospheric pressure. Hurricane eyes average about 20 miles (32 kilometers); the National Hurricane Center reported Dorian’s eye had a diameter of 50 miles (80 kilometers) around the time this image was acquired. Thinner clouds—part of the storm’s higher-level outflow—extended well inland across Georgia, South Carolina, and North Carolina.

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Figure 15: VIIRS on on the Suomi NPP satellite captured this nighttime composite image as the storm approached the coast at 3:42 a.m. Eastern Time (07:42 UTC) on 5 September 2019. At the time, Dorian packed maximum sustained winds of 115 miles (185 kilometers) per hour and was moving north at 8 miles per hour (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS data from the Suomi NPP satellite. Story by Adam Voiland)

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Figure 16: The VIIRS image was captured by the sensor’s 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 gas flares, city lights, and reflected moonlight. Infrared observations from VIIRS were used to enhance the visibility of clouds. Optical MODIS satellite data was layered into the image to make it easier to distinguish between ocean and land surfaces (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS data from the Suomi NPP satellite, and power outage data courtesy of PowerOutage.us. Story by Adam Voiland)

• August 20, 2019: Beginning on August 10, 2019, NASA satellites have observed waves of fire sweeping through forests on Gran Canaria, the second most populous of the Canary Islands. Though the fire has not yet struck major residential and tourist areas, authorities have issued evacuation orders for 9,000 people living in 50 nearby towns and villages. 30)

- The fire is tearing through pine forests in mountainous terrain on the second most populous of the Canary Islands.

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Figure 17: VIIRS on the Suomi NPP satellite tracked the growth of the fire between 14-19 August 2019. The VIIRS “day-night band” is extremely sensitive to low light, making it possible to see the fire front from space at night. Nighttime lights from population centers along Gran Canaria’s coast are also visible, particularly along the eastern half of the island (image credit: NASA Earth Observatory, images by Joshua Stevens, using data from the VIIRS day-night band data from the Suomi NPP. Story by Adam Voiland)

- The fire initially flared up near Tejeda, in the mountainous central part of the island, and then spread rapidly toward the northwest into Tamadaba Natural Park in unusually warm, dry, and windy conditions.

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Figure 18: This map shows land surface temperatures on the afternoon of August 15, a day when temperatures exceeded 49°C (120°F) in some areas. The map is based on data collected by the MODIS instrument on NASA's Aqua satellite. Note that the map depicts land surface temperatures, not air temperatures. Land surface temperatures reflect how hot the surface of the Earth would feel to the touch in a particular location. They can sometimes be significantly hotter or cooler than air temperatures. (image credit: NASA Earth Observatory, image by Joshua Stevens, using data from the Level 1 and Atmospheres Active Distribution System (LAADS) and Land Atmosphere Near real-time Capability for EOS (LANCE), story by Adam Voiland)

- The fire is burning forests of Canary pine (Pinus canariensis), which is among the most fire-tolerant pine species in the world. The trees have several adaptations that allow them to survive and thrive after fires: thick bark that prevents heat damage, trunks that easily sprout new branches; and serotinous cones that depend on high heat to release seeds.

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Figure 19: MODIS acquired this false-color image on 19 August. It is composed from a combination of visible and infrared light (MODIS bands 7-2-1) that help distinguish charred vegetation (black) from unburned vegetation (green). Areas with minimal vegetation appear brown (image credit: NASA Earth Observatory, image by Joshua Stevens, using data from the Level 1 and Atmospheres Active Distribution System (LAADS) and Land Atmosphere Near real-time Capability for EOS (LANCE), story by Adam Voiland)

- Scientists who monitor fire activity in the Canary Islands have observed clear trends in the past half-century. Most notably, the number of fires has decreased even as the number of hectares burned by each fire has increased significantly. On net, fires burn roughly the same average area each year, but they do it in a much more dramatic fashion because they are larger and more intense.

- While increasing temperatures may have contributed to this trend, University of La Laguna scientist José Ramón Arévalo attributes much of the change to more active and effective firefighting efforts that now suppress most fires and lead to a build-up of flammable material in forests. Increased development and tourism also contribute by requiring that firefighters aggressively suppress fires over a wider area.

• August 19, 2019: Our atmosphere behaves like a fluid, changing its flow and direction when it runs into an obstacle. Sometimes we can see (and feel) these movements on a small scale, as winds blow trees and water. Satellites, however, can observe these twists and bends on a broad scale as they create interesting shapes in the sky. 31)

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Figure 20: This image shows spiraling cloud patterns off the coast of Morocco on 19 July 2019. Known as von Kármán vortices, these eddies can form nearly anywhere that fluid flow is disturbed by a solid object. In this case, the vortices formed when winds flowed around small islands in the North Atlantic (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS day-night band data from the Suomi NPP. Story by Kasha Patel, with image interpretation by George Young)

- “The basic idea is that flow over, and around, a mountainous island slows down,” said George Young, professor of meteorology at Penn State University. This creates a vertical wall of whirling air—with faster wind flowing past slower wind below. These sheets can wrap themselves into vortices and shed alternately off the two sides of the island. They can subsequently travel downwind from the island to create “vortex streets,” as seen in this image. The pattern of the spirals depends on the intensity of the wind.

- “This is a spectacular satellite image,” said Paul Beggs, an associate professor at Macquarie University. “I don’t recall having seen an image of von Kármán vortices at nighttime previously, so I would consider it rare.” Atmospheric vortices are commonly observed by satellites, and Earth Observatory has shown them many times. But we have rarely noted them in nighttime imagery.

- Young notes that nighttime von Kármán vortices are not necessarily infrequent occurrences; new sensor technology has just made it much easier to capture these scenes. Satellites now carry shortwave infrared channels and image filters that achieve the spatial resolution and faint light detection to allow researchers to see vortices at night.

- This image was acquired with the “day-night band” of the VIIRS instrument on the Suomi NPP satellite. VIIRS detects light in a range of wavelengths from green to near-infrared and uses filtering techniques to observe dim signals such as city lights, gas flares, auroras, wildfires, and reflected moonlight.

- “I’m not the least surprised to see them at night because the two factors they primarily depend on (wind speed in the boundary layer and a strong stable layer at the top of the boundary layer) vary little between day and night at sea,” said Young. These von Karman vortices also appeared in daylight.

• 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. 32)

- 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 21: 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. 33)

- 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 22: 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 23: 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. 34)

- 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 24: 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 25: 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. 35)

- 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 26: 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. 36)

- 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 27: 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. 37)

- 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 28: 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. 38)

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Figure 29: 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 30: 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.39)

- The nighttime images of Beira’s nighttime lights (Figure 31) 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 31: 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. 40)

- 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 32: 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. 41) 42)

- 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 33: 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 34: 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 35: 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. 43)

- 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 36: 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. 44)

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Figure 37: 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 38: 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. 45)

- 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 39: 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 40: 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. 46)

- “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 41: 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 42) 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. 47)

- 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 42: 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. 48)

- 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 43: 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 44: 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. 49)

- 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 45: This map as well as Figure 46 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 46: 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. 50)

- 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 47 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 47: 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 47: 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 48) 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 48: 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. 51)

- The warm water stretched far beyond La Jolla. The map of Figure 49 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 49: 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. 52)

- The image of Figure 50 show browning in north-central Europe on July 24, 2018. For comparison, the image of Figure 51 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 50: 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 51: 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 52 and 53 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 52: 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 53: 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. 53)

- “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 54: 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 55: 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. 54)

- 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 56) 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 56: 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 57: 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. 55)

- 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 59) 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 58: 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 59: 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. 56)

- 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 60: 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 61: 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. 57)

- 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 62: 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 63: 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. 58)

- In the image of Figure 64, 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 64: 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. 59)

- 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 65: 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. 60)

- 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 66) on March 18, 2018. In the image of Figure 67, 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 66: 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 67: 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)]