On vegetated landscapes, Evapotranspiration (ET) can be simplified as the combination of evaporation from the soil and transpiration from vegetation.
Actual ET (ETa) is produced using the Operational Simplified Surface Energy Balance (SSEBop) model Version 6 (Senay et al., 2013, 2020, 2023) from 2012 to Present using a data stream from the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the NASA/NOAA Suomi National Polar-Orbiting Partnership (Suomi NPP) and NOAA-20 satellites.
The SSEBop model is a thermal-based simplified surface energy model for estimating ETa based on the principles of satellite psychrometry (Senay, 2018). SSEBop Version 6 implementation uses land surface temperature (Ts) from VIIRS with key model parameters (cold/wet-bulb reference, Tc, and surface psychrometric constant, 1/dT) derived from a combination of observed surface temperature, normalized difference vegetation index (NDVI), climatological average daily maximum air temperature (Ta, 1-km) from Daymet and CHELSA, and net radiation data from ERA-5. SSEBop Version 6 also uses the Forcing And Normalizing Operation (FANO), a novel parameterization to better estimate ET in all landscapes and all seasons regardless of vegetation cover density, thereby improving model accuracy by avoiding extrapolation of Tc to non-calibration regions (Senay et al., 2023).
Final ETa is generated as a product of ET fractions generated from remotely sensed VIIRS thermal imagery, summarized every dekad (~10 days) with reference ET generated from weather data fields using the Penman-Monteith Equation (TerraClimate and CSIRO-based datasets).
ETa data and anomaly products (current vs. 2013 – 2022 median), produced at 1 km resolution, are available at: https://earlywarning.usgs.gov/fews.
|Title||SSEBop Evapotranspiration Data from 2012 to Present: Dekadal (10-day), Monthly, Seasonal, and Annual Time Scales|
|Authors||Gabriel Senay, Stefanie Kagone, Gabriel E Parrish, Michael E Budde, James Rowland|
|Product Type||Data Release|
|Record Source||USGS Digital Object Identifier Catalog|
|USGS Organization||Earth Resources Observation and Science (EROS) Center|