Abstract
Evapotranspiration (ET) is a major component of the global and regional water cycle. An operational Geostationary Operational Environmental Satellite (GOES) ET and Drought (GET-D) product system has been developed by the National Environmental Satellite, Data and Information Service (NESDIS) in the National Oceanic and Atmospheric Administration (NOAA) for numerical weather prediction model validation, data assimilation, and drought monitoring. GET-D system was generating ET and Evaporative Stress Index (ESI) maps at 8 km spatial resolution using thermal observations of the Imagers on GOES-13 and GOES-15 before the primary operational GOES satellites transitioned to GOES-16 and GOES-17 with the Advanced Baseline Imagers (ABI). In this study, the GET-D product system is upgraded to ingest the thermal observations of ABI with the best spatial resolution of 2 km. The core of the GET-D system is the Atmosphere-Land Exchange Inversion (ALEXI) model, which exploits the mid-morning rise in the land surface temperature to deduce the land surface fluxes including ET. Satellite-based land surface temperature and solar insolation retrievals from ABI and meteorological forcing from NOAA NCEP Climate Forecast System (CFS) are the major inputs to the GET-D system. Ancillary data required in GET-D include land cover map, leaf area index, albedo and cloud mask. This paper presents preliminary results of ET from the upgraded GET-D system after a brief introduction of the ALEXI model and the architecture of GET-D system. Comparisons with in situ ET measurements showed that the accuracy of the GOES-16 ABI based ET is similar to the results from the legacy GET-D ET based on GOES-13/15 Imager data. The agreement with the in situ measurements is satisfactory with a correlation of 0.914 averaged from three Mead sites. Further evaluation of the ABI-based ET product, upgrade efforts of the GET-D system for ESI products, and conclusions for the ABI-based GET-D products are discussed.
Highlights
The evaporation from the earth’s surface and the transpiration from the vegetation stomata is commonly referred to as evapotranspiration (ET)
ET maps from current operational GOES Imager-based ET and Drought (GET-D) system are at 8 km spatial resolution over the North America domain (Figure 4a) while the upgraded system focuses on the Continental United States (CONUS) at 2 km (Figure 4c)
ET estimates from the upgraded GET-D system were compared with ET ground observations collected from the University of Nebraska Agricultural Research and Development Center near Mead, NE
Summary
The evaporation from the earth’s surface and the transpiration from the vegetation stomata is commonly referred to as evapotranspiration (ET). Due to the relatively low expense and continuous spatial coverage, satellite remote sensing of evapotranspiration has been applied to monitoring regional and global droughts in the recent decades and is probably the most practical and efficient approach to providing the ET data needs for the numerical weather, climate and hydrological prediction models (e.g., [6,7,16,17,18,19,20]). Remotely sensed drought indices based on the land surface vegetation condition (e.g., VegDRI, [25]) are designed to detect poor vegetation health under drought conditions. Based on the aforementioned advantages, NOAA NESDIS scientists selected the ALEXI model to develop an operational GOES Imager-based ET and Drought (GET-D) product system to provide NOAA and other users with daily ET estimates and multi-weekly drought maps for North America [29,30]. Preliminary results of the GOES ABI-based ET are summarized in the last section, along with the discussion about further upgrade of the GET-D system
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