California Statewide Regional and Field Scale Evapotranspiration Mapping Using MODIS & Landsat, and Surface Energy Balance System (SEBS).

We developed a comprehensive framework for spatially mapping daily Actual Evapotranspiration (ETa) using satellite earth observation data and algorithms.  The core of the framework includes satellite imagery, meteorological data, and the Surface Energy Balance System (SEBS).  The SEBS algorithm provides a robust, economical, and efficient tool to estimate ETa using remotely-sensed data. We improved the accuracy and reliability of SEBS for California by including an atmospheric correction algorithm; a daily-reference ET-based extrapolation algorithm (from spatial CIMIS); and a cloud-screening sub-model.  This included spatially interpolated inputs of air temperature, relative humidity, wind speed, solar radiation, and reference ET.  Using the SEBS framework, we produced an unprecedented, daily, 30-meter spatial resolution, statewide ETa dataset from 2010 through 2015.  The dataset was developed using all available imagery for the State of California for the Terra-MODIS and Landsat Sensors (Landsat 5, 7, and 8) from 2010 through 2015.  To put this into perspective, the SEBS framework is leveraging 900-1100 Landsat images per year to produce the ETa results at the statewide scale (26 Landsat scenes in California; 44-46 images per scene/year).  In addition, there are 365 Terra-MODIS images available on a yearly basis, with 230 to 250 cloud free images used in our SEBS framework to produce our ETa results.  We, successfully validated the SEBS dataset using on-the-ground measurements.