SSEBop Evapotranspiration Data

On vegetated landscapes, Evapotranspiration (ET) can be simplified as the combination of evaporation from soil and transpiration from vegetation. Actual ET (ETa) is produced using the Operational Simplified Surface Energy Balance (SSEBop) model (Senay et al., 2013) for 2003 to present using data stream from the Aqua satellite. The SSEBop setup is based on the original Simplified Surface Energy Balance (SSEB) approach (Senay et al., 2007, 2011) with unique and improved parameterizations for operational applications. It combines ET fractions generated from remotely sensed MODIS thermal imagery, summarized every 10 days (dekadal), with reference ET, generated from weather data fields using the Penman-Monteith Equation. The unique feature of the SSEBop parameterization is that it uses a pre-defined, seasonally dynamic surface psychrometer constant parameter that helps define the hot/dry and cold/wet reference limits, unique to each pixel. Furthermore, the "cold/wet limit is determined using the daily maximum air temperature (Ta) using the c factor parameter which relates Ta to land surface temperature at well-vegetated/well-watered surfaces. The original SSEB model was formulated based on an adaptation of the hot and cold pixel principles of SEBAL (Bastiaanssen et al., 1998) and METRIC (Allen et al., 2007) models. NoData pixels are indicated as NoDATA in ArcGIS. However, other software (e.g., ERDAS imagine) show nodata as -32768.00. ETa data and anomaly products (current vs. 2003 2015 median), produced at 1 km resolution, are available at: https://earlywarning.usgs.gov/fews.