Suchergebnisse

ch. 1. Introduction -- ch. 2. What is drought? -- ch. 3. The science of drought -- ch. 4. Quantifying drought -- ch. 5. Palaeo-drought : the occurrence of drought over past millennia -- ch. 6. Drought in the 20th century -- ch. 7. Major drought events of the 20th century -- ch. 8. Drought in the 21st century -- ch. 9. Summary and recommendations.

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) was launched to the International Space Station on 29 June 2018 by the National Aeronautics and Space Administration (NASA). The primary science focus of ECOSTRESS is centered on evapotranspiration (ET), which is produced as Level-3 (L3) latent heat flux (LE) data products. These data are generated from the Level-2 land surface temperature and emissivity product (L2_LSTE), in conjunction with ancillary surface and atmospheric data. Here, we provide the first validation (Stage 1, preliminary) of the global ECOSTRESS clear-sky ET product (L3_ET_PT-JPL, Version 6.0) against LE measurements at 82 eddy covariance sites around the world. Overall, the ECOSTRESS ET product performs well against the site measurements (clear-sky instantaneous/time of overpass: r2 = 0.88; overall bias = 8%; normalized root-mean-square error, RMSE = 6%). ET uncertainty was generally consistent across climate zones, biome types, and times of day (ECOSTRESS samples the diurnal cycle), though temperate sites are overrepresented. The 70-m-high spatial resolution of ECOSTRESS improved correlations by 85%, and RMSE by 62%, relative to 1-km pixels. This paper serves as a reference for the ECOSTRESS L3 ET accuracy and Stage 1 validation status for subsequent science that follows using these data. ; We thank B. Freepartner, M. Sikka, F. Galvan, and R. Littles for software assistance. We thank Peter Blanken, James Cleverly, Higo Jose Dalmagro, Ken Davis, Eric Dufrene, Beverly Law, Marcy Litvak, Kim Novick, Matti Rasanen, Russell Scott, and Dan Yakir for contributing data. The journal editors and anonymous reviewers provided useful suggestions to improve the paper. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. California Institute of Technology. Government sponsorship acknowledged. Support was provided by NASA's ECOSTRESS mission.