TEMPO: Next-generation pollution tracking instrument offers new solutions to old problems

Written by Ben Houser

            When launched in 2022, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument will revolutionize the way scientists observe air pollution and atmospheric chemistry. Hovering 22,000 miles above the equator in geostationary orbit, TEMPO will measure air pollutants over North America every daylight hour; these hourly measurements set TEMPO apart from current air pollution satellites, which are limited in both observation frequency and spatial resolution. TEMPO’s high-resolution hourly measurements will support an array of potential applications, some of which were impossible before TEMPO. For example, public health studies examining the impact of air pollution on health will be possible on shorter timescales than ever before and short-term emissions tracking will give scientists new insight into air pollution.

            The TEMPO instrument is a grating spectrometer, which sweeps a mirror over North America and collects both ultraviolet and visible light that has been scattered by particles in the atmosphere. Based on these measurements, the TEMPO Science Team, led by Principal Investigator Dr. Kelly Chance at the Smithsonian Astrophysical Observatory, are developing science algorithms to extract key information on trace gases, aerosols, and clouds present in the atmosphere. At the center of the field of regard, TEMPO’s spatial resolution of 2.1 kilometers per pixel in the north-south direction and 4.5 kilometers per pixel in the east-west direction. Such high resolution allows TEMPO to monitor pollution at sub-urban scales, tracking air quality within the borders of urban areas and surrounding suburbs.

SPoRT scientist Dr. Aaron Naeger is the TEMPO mission Deputy Program Applications Lead, who is responsible for engaging potential TEMPO end-users, coordinating the pre-launch activities of TEMPO end-users, and leading the TEMPO Early Adopter team. Dr. Naeger does extensive research on air pollution and aerosols, and anticipates the impact that TEMPO will have on his work. “Currently I use low-earth orbit satellite data from the NASA Ozone Monitoring Instrument (OMI) and European Space Agency’s (ESA) Tropospheric Monitoring Instrument (TROPOMI) to track and study air pollution across the globe, which are limited to one or two observations per day over the same area,” Dr. Naeger said. “TEMPO will significantly expand the breadth of my research activities by providing hourly observations of air pollutants from morning to evening across Greater North America.” TEMPO’s capabilities will offer new opportunities to scientists like Dr. Naeger, who are currently unable to track air pollution with such high observation frequency. “These new research activities can include studying the complex chemical evolution of pollutant events throughout the day, source contributions from natural and anthropogenic emissions, and impact of different air pollutants on human health,” said Dr. Naeger.

            As TEMPO end-users await the instrument’s launch in 2022, the TEMPO early adopter program is helping to ensure that their operations and systems are ready for the new data. The program began in 2019 to provide a means of communication between the TEMPO Science Team and end-users, and to ensure end-users are ready to go when the satellite hosting TEMPO reaches orbit (Figures 1 and 2). To accomplish this, NASA SPoRT is distributing several synthetic TEMPO products, including ozone, nitrogen dioxide, sulfur dioxide, formaldehyde, water vapor, and aerosols. These synthetic products mimic future TEMPO data, allowing end-users to configure and troubleshoot their systems pre-launch. On 18-19 May 2020, a joint virtual Early Adopter workshop was held for TEMPO and MAIA, a second air quality instrument launching in 2022. Dr. Naeger led the TEMPO workshop, which included several presentations on TEMPO’s status, applications, and synthetic data.

Fig 1. Synthetic TEMPO data, representing Tropospheric NO2 over the Northwestern United States on 9 August 2013, during the 2013 wildfire season. Active fires and smoke led to the large NO2 amounts in the region.

            Due to TEMPO’s frequent and detailed observations of several air pollutants, there is a wide range of potential applications. One such application is the study of thunderstorms; Dr. Naeger said, “there are a lot of interesting applications but perhaps the most interesting application is focused on the use of nitrogen dioxide observations from TEMPO to monitor and track lightning-produced nitrous oxide in the upper troposphere which can lead to substantial ozone production.” TEMPO may also help researchers understand the relationship between aerosols and tropical cyclones; combining data from TEMPO and other weather tracking satellites will enable researchers to understand how different trace gas and aerosol environments influence the intensity and behavior of tropical cyclones. Researchers plan to use TEMPO for numerous other applications, such as understanding the complex chemistry of smoke plumes from fires, tracking variations in nitrogen oxide emissions from soils in agricultural areas, and monitoring the daily evolution of pollution in areas of complex terrain. 

Fig 2. Synthetic TEMPO data, representing Tropospheric NO2 over California on 13 August 2013. Urban emissions led to enhanced NO2 levels along the Southern coast.

TEMPO’s capability for detailed air quality measurements makes it especially interesting to public health researchers, who study the impact of air quality on human health. “Air quality and epidemiology research studies will be significantly improved through incorporation of TEMPO data,” said Dr. Naeger. “We will be able to understand how different air pollutants impact health by analyzing the hourly TEMPO trace gas products along with health data and records.” Using TEMPO data in air quality models will also lead to more realistic forecasts, and there is a plan to combine TEMPO data with models to improve Environmental Protection Agency’s air quality indices.

In the future, TEMPO will be an important tool in advancing climate change research. “TEMPO can help researchers understand the impact of climate change on air pollution due to wildfires since the hourly observations will effectively monitor the evolution of smoke throughout the day,” said Dr. Naeger. “The longer the TEMPO mission lifetime, the more impact the unprecedented observations will have on climate change research.” A long lifespan means that TEMPO will be able to track changes in the atmosphere over long periods of time, which will reveal even more insight into the role of climate change on air pollution. TEMPO’s climate change research capabilities will be assisted by other satellites around the word: Geostationary Environment Monitoring Spectrometer (GEMS), a similar instrument to TEMPO, was launched over Asia in February 2020. By 2023, a similar air-pollution tracking satellite will also be operational in Europe. This geostationary trio will monitor air pollution and atmospheric chemistry on a global scale. “Utilizing this suite of geostationary observations will be key for global climate change research,” said Dr. Naeger.

SPoRT SST Composite Picks Up Unusual Summertime Tehuano Gap Wind Event

Written by Ben Houser

On 11 June 2020, the National Hurricane Center’s Tropical Analysis and Forecast Branch (TAFB) announced that they were monitoring a Tehuano gap wind event, and issued a Gale warning for the area. On 12 June, the gale force winds continued, and the TAFB forecasted that the strong gap winds would continue into the next week. Typically, Tehuano gap wind events are most common in the winter, with most events occurring between November and March; a gap wind event in June is unusual.

The Isthmus of Tehuantepec is in southern Mexico, bordered by the Gulf of Mexico to the north and the Pacific Ocean to the south. Due to the geography of the Sierra Madre mountain range and the Chivela Pass, a strong gap wind, known as the Tehuano or Tehuantepecer, is periodically forced southward over the Isthmus. The gap wind forms as cold air masses develop to the north in Canada and the U.S., travel southward through the western Gulf of Mexico and eastern Mexico, and meet an impasse at the Sierra Madre mountains. As the cool, dense air mass continue to travel south, the air is forced into the Chivela Pass, where it is compressed through the Pass’s 40-kilometer mountain gap. As the winds travel through the Pass, they accelerate, and often emerge into the Gulf of Tehuantepec with gale, storm, or even hurricane force winds.

Tehuano gap wind events have several meteorological and ecological impacts. The gap wind blows hundreds of miles into the Pacific Ocean, and generates waves that can be observed up to 1600 km away (Hong et al. 2018). The gap wind can cause high wave heights and turbulent water, causing a hazard to sailors and shipping interests. When the gap wind blows, sea surface temperatures (SST) in the Gulf of Tehuantepec cool due to the induced oceanic currents, as warmer surface water is replaced by cooler deep water that rises to the surface. This upwelling pushes cold water, rich with nutrients, to the surface, boosting the underwater ecosystem and making the Gulf of Tehuantepec a fertile fishing ground. As the Tehuano roars, local fishermen set fishing kites into the Gulf, catching hundreds of pounds of fish while avoiding the dangerous water (Vizcarra 2015).

In November 2013, the SPoRT / SERVIR Weather Research and Forecasting (WRF) model was able to generate forecasts that simulated numerous strong Tehuano gap wind events. SPoRT researcher Jonathan Case presented one of these forecasts at the 2013 Marshall Science and Technology Research Jamboree, and authored an accompanying SPoRT blog post.

The rare 11 June gap wind event is unique because it is well out of season. According to NASA’s Global Hydrology Resource Center’s Regional Air-Sea Interactions dataset, which logs Tehuano gap wind speeds and sea surface temperatures from 1998 to 2011, wind events in June are sparse. The dataset does not indicate any SST cooling events occurring in June between 1998 and 2011 (Li and Smith, 2014). In the warm spring and hot summer, it is rare that the cold air masses over Canada and the US will reach the Gulf of Mexico.

The 11-12 June Tehuano gap wind event caused significant sea surface cooling in the Gulf of Tehuantepec, which the SPoRT SST Composite product detected. The SPoRT SST Composite combines several SST satellite retrievals and data sources to compute reliable SST across the Northern Hemisphere. SPoRT SST imagery from June 12 (Fig. 1) shows typical, warm temperatures in the Gulf of Tehuantepec prior to the upwelling associated with the gap wind event. However, imagery from 13 and 14 June reveal SST cooling following the gap wind event. On 13 June, the Gulf begins to cool (Fig. 2), and imagery from 14 June (Fig. 3) reveals significant cooling of 3 to 4 degrees Celsius due to upwelling of colder water caused by the gap wind event and induced oceanic circulation.

Fig. 1. SPoRT SST Composite Imagery at 0600 UTC 12 June 2020, of the Isthmus of Tehuantepec.
Fig. 2. Same as in Fig. 1, except valid at 0600 UTC 13 June 2020.
Fig. 3.  Same as in Fig. 1, except valid at 0600 UTC 14 June 2020.

References

Hong, X., Peng, M., Wang, S., Wang, Q. 2018. Simulating and understanding the gap outflow and oceanic response over the Gulf of Tehuantepec during GOTEX. Dyn Atmos Ocean. 82:1–19. https://doi.org/10.1016/j.dynatmoce.2018.01.003.

Li, X. and D. Smith. 2014. Regional Air-Sea Interaction (RASI) Gap Wind and Coastal Upwelling Events Climatology Gulf of Tehuantepec, Mexico. Data sets available online [http://ghrc.nsstc.nasa.gov/] from the NASA EOSDIS Global Hydrology Resource Center Distributed Active Archive Center, Huntsville, Alabama, U.S.A.

Vizcarra, N. 2015. Tracing the Tehuano. NASA Earth Science Data and Information System, Sensing Our Planet. https://earthdata.nasa.gov/learn/sensing-our-planet/tracing-the-tehuano.

Lightning Safety Awareness Week June 21-27, 2020

Written by Chris Schultz, Kelley Murphy, and Ben Houser

Lightning Safety Awareness week is in its 20th year within the United States. Each year this week is held in June to remind people of the dangers that lightning can pose to people and infrastructure.  Over the last 20 years, there has been a steady downward progression in the average number of lightning fatalities within the US from around 55 per year in 2001 to under 30 in present day. Much of this decline is the direct result of awareness generated by NOAA slogans like “When Thunder Roars, Go Indoors” or “See a Flash, Dash Inside” for the deaf and hard of hearing community.

Despite these efforts, North Alabama has seen three lightning fatalities in the last four years. In each case, the victim was near the edges of the precipitation and thunder was audible.  Research indicates that approximately 47% of lightning victims are struck after the storm passed their location (Holle et al. 1993).  An additional 35% of victims are struck as the storm approached their location. Thus, many of the lightning deaths occur when it is not raining at the victim’s location. Thus, lightning deaths can and have occurred when it is not raining at the victim’s location.

Figure 1 – Lightning casualties as a function of lightning risk (number of flashes overhead; orange) versus the exposure of people to the risk (people located outside with a nearby storm; yellow). Original Image, John Jensenius, NWS Retired, annotation from NASA SPoRT.

Lightning is one of the fundamental focus areas of the Short-term Prediction and Research Transition (SPoRT) Center. The SPoRT team is constantly working to develop new products to improve situational awareness and assessment of lightning risk for operational forecasters and the public.  The team works directly with emergency management, forecasters at the National Weather Service, and other partners at Marshall Space Flight Center to work toward improving lightning safety, while mitigating lost time due to lightning protocols. 

There are two specific areas in which SPoRT is actively working to improve lightning situational awareness. The first is the development of the Stoplight product, launched in 2018 to help a stakeholder understand when the last lightning to impact their location occurred (Figure 1).  The motivation for this product is that the National Weather Service and the National Lightning Safety Council advise a 30-minute rule for when an individual hears the last thunder at their location. It can be difficult to remember exactly when that last lightning flash occurred, so Stoplight provides the user with an easy to read interface that allows them to make the best decision possible based on lightning data. This product has been used at Marshall Space Flight Center’s Emergency Operations Center since 2018. Stoplight is currently being modified and extended into the National Weather Service through a new product named Time Since Last Flash, which merges all available NOAA lightning datasets to produce a unified field across the areas of responsibility of the National Weather Service.

Figure 2 – Example of the GLM stoplight product developed to help end users understand the time of the last lightning flash at their location, so they can return to outdoor activities safely as a storm moves away.  Adapted from Stano et al. (2019).

The second area of growth is the development of a real-time risk assessment that can provide an end user with a depiction of risk due to lightning exposure at any given time. This would allow the end user to make informed decisions, such as when it may be necessary for people to seek shelter before seeing lightning or hearing thunder. The application of different risk tolerability frameworks also provides an opportunity to assess how people may perceive lightning risk in different scenarios. Examples of the lightning risk assessment are included in Figure 3, applied to two of the fatality cases from North Alabama.  At the time that both persons were struck, their risk was in the unacceptable category. With more research and development, the hope is that this tool will help continue to reduce the exposure of people to the lightning threat and can be applied to lightning safety scenarios globally.

Figure 3 – Lightning risk assessment for the two fatalities in North Alabama during July 2016. The colored backdrop corresponds to risk levels due to lightning: red indicates an unacceptable risk, yellow is a tolerable risk, and green is an acceptable risk. The dashed line indicates an alternate tolerability/decision threshold over which to assess the level of risk. Adapted from Murphy et al. (2020), Weather Climate and Society, conditionally accepted, pending revision.

So, as we move into the heat of summer in the United States, when lightning fatalities are greatest within the United States, be aware of your surroundings, and when Thunder Roars, Go Indoors!

References

National Lightning Safety Council, 2020: http://lightningsafetycouncil.org/

Holle, R. L., R. E. Lopez, R. Ortiz, C. H. Paxton, D. M. Decker, and D. L. Smith, 1993: The local meteorological environment of lightning casualties in central Florida. Preprints, Conference on Atmospheric Electricity, October 1993, St. Louis, MO, Amer. Met. Soc.

Murphy, K. M., E. C. Bruning, C. J. Schultz, and J. Vanos, 2020: Assessing lightning risk in outdoor vulnerable environments, Wea. Clim. and Society, conditionally accepted, pending revision.

Stano, G. T., M. R. Smith, and C. J. Schultz, 2019: Development and evaluation of the GLM stoplight product for lightning safety. J. Operational Meteor., 7 (7), 92-104, doi: https://doi.org/10.15191/nwajom.2019.0707

SPoRT’s Role in the SWOT Early Adopter Program

By Ben Houser

Between May 26 and June 1, 2020, a virtual hackathon was hosted by the University of Washington for SWOT early adopters. SWOT, or Surface Water and Ocean Topography, is a joint mission between NASA’s Jet Propulsion Laboratory (JPL) and the French space agency, The National Centre for Space Studies (CNES), with contributions from the Canadian Space Agency (CSA) and the UK Space Agency. The SWOT satellite observatory will survey surface and ocean water around the globe, collecting data with groundbreaking resolution. SWOT is the first satellite mission to ever survey water level on a global scale, and its data will have a major impact on a number of applications.

Along with fifteen other groups, NASA SPoRT is a member of the SWOT Early Adopter Program; these early adopters are preparing to integrate SWOT data into their projects. When the SWOT satellite observatory is launched by a SpaceX Falcon 9 rocket in 2022 and begins collecting data, SWOT early adopters will be prepared to use this data in a variety of applications. The SWOT Hackathon was designed to engage early adopters and help them overcome technical issues they may have experienced. SPoRT scientist Dr. Nicholas Elmer participated in the hackathon as a presenter and “hacker helper,” assisting early adopters in the use of the CNES SWOT hydrology data simulator.

The SWOT satellite observatory will carry a number of instruments to facilitate data collection. A JPL-developed Ka-Band Radar Interferometer, or KaRIn, will be the primary instrument used to collect water level data. KaRIn, which utilizes two antennas, will work by transmitting a signal from one antenna, and then receiving the same signal back with both antennas after it bounces off of the earth’s surface. The phase difference between these two signals will be used to calculate water level with extreme precision; over the ocean, SWOT’s data will be accurate down to about a centimeter, over an area of 125 km at any given time. SWOT will collect data in 21-day cycles, during which the entirety of the globe, excluding the poles, will be observed. The satellite observatory will also carry an altimeter, a DORIS antenna to receive signals from Earth, a radiometer to measure water vapor between SWOT and the surface, an X-band antenna for data downlink, and a GPS receiver.

As a SWOT early adopter, SPoRT is preparing to integrate SWOT data into the NOAA National Water Model and the SPoRT Land Information System (or LIS) product. For his PhD dissertation, Dr. Nicholas Elmer developed a method to assimilate SWOT data into the WRF-Hydro modeling system, which is the backbone of the NOAA National Water Model. As a SPoRT scientist, Dr. Elmer is taking the next step to include SWOT data in the SPoRT LIS product. Dr. Elmer plays a key role in the SWOT early adopter process, as he contributed to the CNES-developed SWOT data simulator, which early adopters use to ensure their applications will function correctly with SWOT data. Dr. Elmer was one of the first early adopters to make use of the simulator, and wrote the tutorial used by early-adopters at the hackathon. During the hackathon, Dr. Elmer assisted international researchers who were working on integrating SWOT data into local hydrological models. Dr. Elmer also contributed code to the simulator that allowed it to create a time series of simulated SWOT data with varying water surface elevations, which CNES adopted into the official simulator distribution.

Example of CNES SWOT simulator pixel cloud (point-based water surface elevations; small circles, no outline) and spatially-averaged water surface elevations (large circles with black outline) along the Nenana River in Alaska. Figure adapted from Elmer et al. (2020).

Throughout the early adopter process, SPoRT has been providing valuable feedback to NASA and CNES. Due to its focus on research to operations and research to applications, SPoRT has provided a unique perspective, communicating the need for low-latency SWOT products for use in operational and near-real-time systems. When SWOT launches, it will bring major improvements to a wide array of applications: SWOT will vastly improve our understanding of Earth’s bodies of water, and will benefit forecasters, scientists, oceanographers, hydrologists, and many others. SWOT will also improve understanding of changing lake, reservoir, and river volumes, which will allow scientists to understand fresh water availability. SWOT’s observations of the ocean will improve scientists’ understanding of global climate change, pollution, and environment stability. SWOT is a major breakthrough in water observation, and SPoRT is playing a small but important role in its development.

References:

Elmer, N. J., C. R. Hain, F. Hossain, D. Desroches, C. Pottier (2020), Generating proxy SWOT water surface elevations using WRF-Hydro and the CNES SWOT Hydrology Simulator, Water Resources Research, American Geophysical Union, Early Online Release, https://doi.org/10.1002/essoar.10502399.1.

Undergraduate Student Highlight: Nicholas Johnson

Written by Ben Houser

Nicholas Johnson has just graduated from the University of Alabama in Huntsville, earning a bachelor’s degree in Earth System Science with a concentration in Atmospheric Science. To earn this degree, Nicholas was required to complete an undergraduate capstone project in his field of study, which he accomplished with the help of SPoRT. Nicholas’s project was the creation of a wind speed adjustment factor that would allow scientists to estimate the surface wind speed in tropical cyclones based on wind speed at higher altitudes. Once its accuracy is tested, this adjustment factor may prove useful to hurricane researchers and forecasters, as it will allow scientists who fly aircraft through storms to predict wind speeds near the surface.

Since he was young, Nicholas has been interested in studying the weather. He chose UAH due to his interest in atmospheric science; the UAH Atmospheric and Earth Science Department provides students with a wide array of unique opportunities. While at UAH, Nicholas took advantage of these opportunities, working on research projects concerning severe weather, meteorology and aviation, and remote sensing technology. Through the UAH Honors College, Nicholas collaborated with the National Weather Service in Memphis, TN, in 2018 to investigate abrupt changes in wind speed at the Memphis International Airport. During the summer of 2019, Nicholas interned at NOAA’s Atlantic Oceanographic and Meteorological Laboratory, where he worked with Hurricane Research Division scientists. The project consisted of finding new ways of organizing data collected by NOAA Hurricane Hunter aircraft and developing new visualizations of aircraft data from tropical cyclones. Nicholas spent his time coding for the project and meeting with scientists to discuss the project, while also attending regular science meetings which included scientists from NOAA and the University of Miami. During the internship, Nicholas had the opportunity to fly with NOAA scientists on a Hurricane Hunter aircraft; Nicholas said watching the sunrise while flying above the storm was one of the most breathtaking experiences of his life. Nicholas’s work with NOAA resulted in a consolidated dataset that combined measurements from various instruments, making it significantly easier for researchers to work with data gathered from Hurricane Hunter aircraft. The project also involved exploring the relationship between aircraft-measured wind speeds and surface wind speeds; this aspect of the NOAA project evolved into Nicholas’s undergraduate capstone project.

Nicholas standing beside one of the NOAA Hurricane Hunter aircraft after a flight into Tropical Storm Barry in July 2019.

In his work with SPoRT, Nicholas relied on NOAA Hurricane Research Division data that included the temperature, pressure, storm structure, high-altitude wind speed, and surface wind speed of tropical cyclones. Nicholas’s goal was to produce an adjustment factor that would allow researchers to convert aircraft-measured wind speed to surface wind speed. Through the analysis of hurricane data, Nicholas produced multiple tables of this adjustment factor based on elements such as storm intensity and the research aircraft’s altitude. Once they are tested for their accuracy, these tables would be used by forecasters, such as those at the National Hurricane Center, to assist in forecasting hurricanes. These tables would allow the National Hurricane Center to make more detailed forecasts, and allow them to more accurately determine a hurricane’s category. More detailed hurricane forecasts result in more thorough emergency-preparedness, and Nicholas’s work could allow authorities more time and information to ensure public safety.

Vertical profile of Nicholas’s wind speed adjustment factor from 0-18 km in altitude. This is from one center pass during a flight in Hurricane Irma on September 5, 2017. The empty space in the middle of the figure at 0 km radial distance is the eye of the storm. The warmer colors indicate surface wind speed is greater than flight level wind speed while the cooler colors indicate surface wind speed is less than the flight level wind speed.

SPoRT has been helpful in Nicholas’s project, as it has provided a community in which Nicholas was able to receive valuable feedback on ideas and interact with scientists who are working on similar projects. At SPoRT, Nicholas spent his time working on code to analyze data, drawing conclusions from analysis, and generating visualizations of his conclusions. Nicholas frequently met with other SPoRT scientists to discuss projects and compare research.

            In the fall, Nicholas will continue to research tropical cyclones as a graduate student at the University of Albany in Albany, New York.

The Rumble Heard ‘Round the Valley

Written by Chris Schultz and Brian Carcione

Hear a long rumble and several loud bangs around 06:22 pm CT last night?  You weren’t alone if you were in the Tennessee Valley.  While severe storms were ongoing in Southern Mississippi and Alabama, a large shield of moderate stratiform rain was parked over Northern Alabama. Most of the time things were quiet, but at 06:22 pm CT, thunder shook the entire Tennessee Valley.

Looking at the lightning data available from the Geostationary Lightning Mapper (GLM), National Lightning Detection Network (NLDN), and NASA Marshall’s Lightning Mapping Array (NALMA), we can pinpoint the extent, the origin, and the number of contributing lightning flashes to this loud rumble that lasted 7-10 seconds.

From the GLM perspective, a large swath of lightning was observed extending northward from South Central Alabama at 06:22 pm CT (Figure 1a). Using information from a real-time long flash detection algorithm from Peterson (2019), there was a series of 2 flashes that occurred within 1 second of each other. One was approximately 267 km long and propagated along the AL/MS border, while the second occupied much of Central Alabama and was approximately 253 km long.  The NALMA also indicates this dual propagation path structure over West Central and Central Alabama (Figure 1b).

Figure 1 – (top, a.) GLM Flash Extent Density between 2320 and 2325 UTC on 19 April 2020.  Underlaid is GOES-16 10.35 µm brightness temperature.  (bottom, b.) NASA Marshall’s North Alabama Lightning Mapping Array data from 2320-2330 UTC. Blue dots indicate the path of lightning flashes during this period, with two paths going northward from the strong storms in South Alabama.

105 lightning flashes were observed in the state of Alabama between 06:22:35 pm and 06:22:39 pm CT (Figure 2a).  Zooming in on the Tennessee Valley (Figure 2b), 11 NLDN points were observed in the National Weather Service County Warning area. Nine of these were positive cloud-to-ground strokes, or strokes typically characterized by strong electric fields, with peak amplitudes between 46 and 202 kA. Positive strokes make up less than 5% of all lightning strikes (NWS), but are well known to occur in vast stratiform regions (e.g., Makowski et al. 2013 and references therein).

Figure 2 – NLDN data between 23:22:35 UTC and 23:22:39 UTC on 19 April 2020.  Left shows flashes in all of Alabama during this time, right shows a zoomed in version of the Tennessee Valley. 

Indicators of electrification visible in the radar data for nearly the previous hour across West Central Alabama. In Figure 3, horizontal reflectivity is mostly uniform; however, examination of differential reflectivity (ZDR) at 1.3 degrees suggests the formation of depolarization streaks. The orientation of snow crystals in thunderstorm clouds is often altered in the presence of strong electric fields and this can produce noticeable cross-coupling between radar signals at the horizontal and vertical polarizations, when both signals are present (Ryzhkov and Zrnić 2007, Kumjian 2013). This leads to the presence of “streaks” in the ice crystals, which are visible in ZDR. Such streaks were present to the southwest and southeast of the KHTX radar at Hytop, AL, and are located above the melting layer (Fig 3b).

Figure 3 – Radar data at 2319 UTC from the NWS radar at Hytop, Alabama (KHTX).  Left is horizontal reflectivity, and right is differential reflectivity at 1.3 degrees elevation.  Depolarization streaks are denoted in red ovals, and the melting layer is identified by orange arrows.

At this point, it’s unclear what percentage of depolarization streaks are followed by lightning occurrence, but the depolarization streak does indicate the potential for lightning. With additional work and operational testing, the depolarization streak could be a useful for Integrated Decision Support Services such as airport weather warnings. Thus, there are potentially additional fusion techniques to develop between the radar and lightning data to anticipate and confirm lightning presence in these low flash rate situations.

References

Kumjian, M. R., 2013: Principles and applications of dual-polarization weather radar. Part III: Artifacts. J. Operational Meteor., 1 (21), 265-274, doi: http://dx.doi.org/10.15191/nwajom.2013.0121.

Makowski, J. A., D. R. MacGorman, M. I. Biggerstaff, and W. H. Beasley, 2013: Total lightning characteristics relative to radar and satellite observations in Oklahoma Mesoscale Convective Systems. Mon. Wea. Rev., 141, DOI: 10.1175/MWR-D-11-00268.1

Peterson, M., (2019), Research applications for the Geostationary Lightning Mapper Operational Lightning Flash Product, J. Geophs. Res., 17-18, https://doi.org/10.1029/2019JD031054

Ryzhkov, A.V. and D.S. Zrnić, 2007: Depolarization in Ice Crystals and Its Effect on Radar Polarimetric Measurements. J. Atmos. Oceanic Technol., 24, 1256–1267, https://doi.org/10.1175/JTECH2034.1

New-generation satellite observations monitor air pollution during COVID-19 lockdown measures in California

Written by Dr. Aaron Naeger

Preventative measures recently adopted to prevent further spread of COVID-19 in the U.S. have prompted an overall slowdown in economic activity and fewer vehicles on the roadways.  Since combustion engine powered vehicles can represent a major source of nitrogen dioxide (NO2) emissions, less traffic on the roadways may lead to a significant reduction in NO2 concentrations and, as a result, fine particulate matter (Particulate Matter less than 2.5 microns in diameter or PM2.5) as NO2 emissions are a known precursor to PM formation.

The Tropospheric Monitoring Instrument (TROPOMI), launched in 2017 as part of the polar-orbiting European Space Agency’s (ESA) Sentinel-5 precursor (Sentinel-5P) satellite, has advanced our capability to monitor fine-scale emission sources, including vehicular emissions along traffic corridors, with unprecedented spatial resolution of 5.6 x 3.5 km2.  Daily midday scans of TROPOMI over the densely populated cities and heavily trafficked corridors in California during March 2020 show how the adoption of stricter COVID-19 measures have impacted air quality in the state.  To effectively examine the changes in air quality in California, we constructed weekday averaged NO2 maps for March at 0.05° grid spacing from high-quality, cloud-free retrievals provided by TROPOMI level 2 data.  It is also important to note the role of natural weather variability on air pollutants during this seasonal transitional period, as warmer temperatures and higher mid-day solar angles lead to shorter NO2 lifetimes and generally lower NO2 column concentrations.

tropomi_march2020_4up_v2

Figure 1. a) Gridded 0.05 x 0.05° NO2 map from TROPOMI Offline (OFFL) L2 retrievals during 2-6 March 2020 (pre-shutdown) over California.  b-d) Same as a), except valid for b) 9-13 March during soft shutdown measures, c) 16-20 March when “shelter in place” orders were announced, d) full period of “shelter in place” orders during 23-27 March. Panel d) generated using near real-time (NRT) product due to 7-10 day lag of OFFL product.

For the first weekday period of March (2-6 March) when COVID-19 measures were yet to be implemented, the largest tropospheric NO2 concentrations were observed in Los Angeles and bordering counties with a less prominent peak in NO2 around San Francisco (Fig. 1a).  The TROPOMI scans also resolved areas of enhanced NO2 along the heavily trafficked corridor of State Route 99 (SR-99) in the Central Valley, particularly around the cities of Bakersfield and Fresno.  As initial, soft COVID-19 measures were adopted by businesses in California during the second weekday period in March (9-13 March), TROPOMI observed strong reductions in tropospheric column NO2 around the large cities of Los Angeles and San Francisco along with noticeable decreases along SR-99 (Fig. 1b).  As California announced statewide “shelter in place” orders during the third weekday period of March (16-20 March), further decreases in NO2 were apparent throughout all populated areas in the state and along SR-99 (Fig. 1c).  Noticeable decreases in NO2 continued throughout much of the state during the fourth weekday period of March (23-27 March), especially around San Francisco (Fig. 1d).  Overall, these observed reductions in TROPOMI NO2 throughout March are the result of decreased emissions on top of the seasonal changes in meteorological conditions.

SPoRT Graduate Student Spotlight: Holley Kenward

Written by Ben Houser

SPoRT is home to several graduate researchers, who are each working on completing the research required to earn their master’s degrees. Previously, we have featured the work of Sebastian Harkema, Angela Burke, and Abby Whiteside. Now, we are featuring Holley Kenward and her research into tropical cyclones. Holley has completed her undergraduate degree in Earth System Science with a concentration in Atmospheric Science at the University of Alabama in Huntsville.

SPoRT_Holley

Holley presenting her research at the Marshall Space Flight Center Jamboree in February of 2020

Holley is researching the diurnal cycles of tropical cyclones, or the daily patterns of tropical cyclones’ intensity and structure. By studying these daily changes in tropical cyclones, Holley is discovering how they impact changes in tropical cyclones’ moisture content. Along with data from a numerically simulated cyclone, Holley uses observations of Hurricane Dorian, which struck the Bahamas with extreme intensity in 2019, to conduct her research. Using imagery from the GOES-16 satellite series and NUCAPS weather soundings, Holley has discovered a distinct diurnal cycle in Hurricane Dorian. In other words, the hurricane exhibited a daily pattern of increase in size and water vapor content that occurred on multiple days. The same diurnal cycle was found in Holley’s numerically simulated hurricane, indicating the great potential of her research. As NASA prepares to launch the TROPICS satellites series, which will provide groundbreaking observation of tropical storms, Holley is working with TROPICS proxy data in her research to determine the data’s potential for understanding hurricanes.

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GOES-16 Low-level Water Vapor in Hurricane Dorian at 3 and 16 Local Time on August 28, 2019. The black rings are every 100km from storm center. There is a very clear increase in overall storm size and water vapor content in the afternoon denoting the diurnal cycle change within Hurricane Dorian.

Holley learned about SPoRT as a freshman at UAH, when she played for the atmospheric science department softball team with a few SPoRT graduate students. As a senior about to graduate, Holley reached out to SPoRT to ask about graduate research positions. When she found about the TROPICS mission and the research associated with it, she was sold!

Holley’s favorite part of working for SPoRT has been the opportunities it has provided her. With the help of SPoRT, Holley has presented her research at the Marshall Space Flight Center Jamboree in February, and has attended the 2nd TROPICS Applications Workshop in Miami, FL. Holley appreciates SPoRT’s help with meeting and learning from other scientists, and the amount of learning she finds within the department itself. She also enjoys doing research that will go into a useful product for operational meteorologists.

In the future, Holley plans on finishing up her masters. When she graduates, Holley would love to continue working with SPoRT, but will be happy as long as she can keep studying tropical cyclones!

2nd NASA TROPICS Applications Workshop in Miami, FL

2nd NASA TROPICS Applications Workshop in Miami, FL

By Ben Houser

            On February 19 and 20, 2020, the second TROPICS (Time-Resolved Observations of Precipitation Structure and Storm Intensity with a Constellation of Smallsats) Applications Workshop occurred in Miami, FL. The workshop’s purpose was to both connect scientists with TROPICS early adopters, or scientists who are performing pre-launch research to determine the mission’s capabilities, and potential end-users, and to discuss the mission’s status and direction. The workshop was organized by SPoRT scientist and TROPICS Deputy Program Applications Lead Dr. Emily Berndt, and University of Miami and NOAA/Hurricane Research Division scientist Dr. Jason Dunion. Along with Dr. Berndt, SPoRT scientists Dr. Erika Duran, Dr. Patrick Duran, and graduate student Holley Kenward attended the conference to engage with early adopters. Attendees included algorithm developers, applied researchers, forecasters, and international representatives from Brazil’s National Institute for Space Research, Météo France, and the European Centre for Medium-Range Weather Forecasts.

TROPICS is a series of small satellites launching no earlier than 2021 that will measure the temperature, humidity, and precipitation of tropical regions with state-of-the-art accuracy and unprecedented frequency. TROPICS’s primary mission objective is to provide a means for end-users to observe hurricanes, and the satellite series will be able to provide high-resolution data of both a hurricane’s eye and the surrounding environment. Using TROPICS, scientists will be able to understand the relationship between temperature, humidity, and precipitation as a hurricane evolves. In 2018, the SPoRT team began the TROPICS Early Adopter program in order to connect potential end-users with TROPICS researchers.

The workshop’s primary purpose was to connect early adopters and potential end-users to TROPICS’s Science Team. Early adopters shared their results and expressed successes, challenges, and future needs. Furthermore, early adopters helped identify technical and visualization enhancements which would make TROPICS data easy to use in a broad range of applications and enable users to quickly adopt the data after launch. During breakout sessions, attendees discussed mission latency, needs for tools and visualizations, and the strengths/limitations of using small satellites in applied research and operations (Fig. 1).

Fig 1: Attendees at the 2nd TROPICS Applications Workshop discuss the value of TROPICS products to support research and applications related to tropical cyclone analysis and forecasting during a breakout session on community needs for products, tools, and visualizations. Right to Left: Holley Kenward (Univ of Alabama in Huntsville-NASA SPoRT), Jason Dunion (Univ of Miami/CIMAS- NOAA/HRD), Derrick Herndon (Univ of Wisconsin-Madison/CIMSS), Stephanie Stevenson (CIRA/NHC), Erika Duran (Univ of Alabama in Huntsville-NASA SPoRT) and Patrick Duran (NASA MSFC SPoRT).

            During the workshop, presentations were given by SPoRT scientists Dr. Emily Berndt and Dr. Erika Duran. Dr. Berndt, who organized the event with Dr. Jason Dunion, presented on the workshop’s plan and expectations and introduced the objectives of each breakout session. Dr. Duran presented on her research analyzing hurricanes using TROPICS proxy data, which is data that mimics what TROPICS data will look like once launched (Fig. 2). Further presentations were given by other scientists on applied research, modeling, and applications relating to precipitation, disasters, and severe weather.

Fig 1. Comparison of temperature between a simulation of a hurricane (blue line) and TROPICS proxy data (green line). Snapshots of temperature are taken at midnight (0:00 local time) just outside the core region of the hurricane. The general similarity of the shape and sign of both temperature profiles suggest a good agreement between the two datasets.

New NUCAPS Training & Resources

SPoRT has been part of a multi-organizational collaboration within the JPSS Sounding Initiative to develop products from Hyperspectral Infrared Sounders and assess the utility of the new observations in the operational environment.  Many of the products and capabilities start out as a “proof of concept” and are then introduced to end users to incorporate end user feedback into the design and implementation process, one example of this is Gridded NUCAPS.   The team has focused on satellite soundings processed through the NOAA Unique Combined Atmospheric Processing System (NUCAPS) which is the NOAA operational satellite sounding retrieval algorithm for hyperspectral infrared sounders on S-NPP and NOAA-20.  Currently NOAA-20 NUCAPS Soundings and Gridded Products are available to all National Weather Forecast Offices.   A recent article “Adapting Satellite Soundings for Operational Forecasting within the Hazardous Weather Testbed” highlights the applied research, assessment of satellite soundings in a quasi-operational setting, and the role of end-user feedback in adapting products/capabilities to meet end users’ needs.  The team comprised of algorithm developers, product developers, and end users has found ways to interact, translate science to operations/operations back to science, leveraging the cross-benefit of science and applications to guide applied research to improve satellite sounding algorithms and products.

The success of NUCAPS for the Cold Air Aloft aviation hazard and diagnosing the pre-convective environment along with the accessibility of NUCAPS products to end users has led to applied research to assess the utility of products for additional applications (Berndt et al. 2020).  NASA’s 2017 Decadal Survey points out “The final missing piece of applications research in the agencies is the very initial phase of creating applications—supporting studies that have an idea about how an application might work, and then attempting to create a community for it, and demonstrate its utility”.  There are complex barriers that exist when identifying end users and transitioning relevant data to meet their needs.  As pointed out by NASA’s 2017 Decadal Survey  “… the applications field is becoming associated with a science of its own…”  Recently, SPoRT has investigated the utility of NUCAPS products for fire weather applications as a “proof of concept”.  As SPoRT engages with users on application of NUCAPS observations, a new interactive training  was developed to communicate the value and utility of these data.  SPoRT has found that creating short, focused, applications-based training can remove some barriers to end users integrating new data and capabilities in operations.   Last SPoRT has created a NUCAPS webpage where scientist and users can find information relevant to NUCAPS products, resources such as training, blogs, peer-reviewed literature, and data access.

Training

New Interactive training on application of NUCAPS products to assess fire weather conditions –> Go to training

Landing_page

NUCAPS resource webpage for scientists and end users –> Go to webpage