Page 140 - GIS for Science, Volume 3 Preview

FLOODING AND DROUGHT
Water is an essential requirement for life. It is in the atmosphere above us; the oceans, lakes, and rivers around us; and the soil and rocks beneath us. It is also locked in the snow, ice caps, and glaciers that cover a good part of the planet. NASA’s remote sensing data helps us understand the availability and distribution of Earth’s water and the impacts of climate change on the processes of the water cycle—evaporation, advection, convection, and precipitation. Using this data and other information, scientific studies have found changes in the spatial and temporal variability of precipitation: wet regions are becoming wetter, dry regions are becoming drier, and extreme events such as floods and droughts are becoming more frequent and intense. Researchers track the sensitivity of precipitation to climate change in terms of intensity, spatial patterns, and frequency of consecutive wet and dry days. Extreme precipitation events exert stresses on soil moisture and on stream and river flow, whereas the lack of rain stresses vegetation and water reservoirs, and when the drought frequency increases, water reservoirs are less likely to recover before the next dry spell.
NASA’s Earth Observing System (EOS) is a coordinated series of polar-orbiting and low-inclination satellites for long-term global observations of the land surface, biosphere, atmosphere, and oceans. NASA’s Goddard Earth Sciences Data and Information Services Center archives EOS data related to atmospheric composition, the carbon cycle and ecosystems, weather and climate variability, and the water and energy cycles. NASA will design a new set of Earth-focused missions called the Earth System Observatory (ESO) to provide key information to guide efforts related to climate change, disaster mitigation, fighting forest fires, and improving real-time agricultural processes. Each satellite in the ESO will be uniquely designed to complement the others, working in tandem to create a 3D, holistic view of Earth, from bedrock to atmosphere.
The Integrated Multi-satellitE Retrievals for Global Precipitation Measurement
The Global Precipitation Measurement (GPM) mission is an international project of NASA and JAXA—the Japan Aerospace Exploration Agency. The program estimates surface precipitation over most of the globe. Its key components are the Orbiting Core Observatory carrying the GPM Microwave Imager (GMI) and a special instrument called the Dual-frequency Precipitation Radar (DPR). The GMI and DPR also serve as precipitation and radiometric standards for a virtual constellation of partner satellites. Both capture precipitation intensities, horizontal patterns, and the vertical structure (profiles) of hydrometeors.
The complex algorithm called the Integrated Multi-satellitE Retrievals for GPM (IMERG, Huffman, et al. 2019) optimally fuses precipitation estimates from this partner constellation with the Core Observatory, geostationary infrared sensors, and rain gauges to produce half-hourly near-global estimates at 10 km resolution.
The early and late products are available approximately four hours (early) and 14 hours (late) after a satellite observation. The IMERG final satellite-gauge product combines the satellite observations with monthly gauge analyses data and is available approximately 3.5 months after the observations. Each successive IMERG run provides a better estimate by including more data in exchange for a longer latency.
IMERG precipitation and quality index of precipitation variables are valuable mainly for their fine spatial and temporal resolution. Researchers use them to study precipitation microphysics, storm structures, and large-scale atmospheric
0 500 kilometers
Accumulated rainfall from August 30 to September 5, 2019, during Hurricane Dorian, a Category 5 hurricane on the Saffir–Simpson scale, battered the Commonwealth of The Bahamas and the East Coast of the United States. The accumulated rainfall map is derived from a GPM IMERG final run.
processes. The long temporal span of GPM IMERG, dating to the year 2000, allows scientists to study Earth’s water cycle, climate variability, climate sensitivity, and feedback processes.
This information allows scientists to issue expedited estimates of accumulated precipitation during an extreme event such as a hurricane, including its spatial extent. It also allows for timely updates regarding landslide potential and early warnings for potential flooding downstream. The use of rainfall data can help forecast crop yields, monitor freshwater resources, and assess hazards related to glacial lakes.
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