Evaluation of actual evapotranspiration rates from the Operational Simplified Surface Energy Balance (SSEBop) model in Florida and parts of Alabama and Georgia, 2000–17

First posted August 24, 2021 For additional information, contact: Director, Caribbean-Florida Water Science CenterU.S. Geological Survey4446 Pet Lane, Suite 108Lutz, FL 33559 Evapotranspiration (ET) is the water-vapor flux transported from surface of Earth into atmosphere and sum water directly evaporated subsurface transpired by plants. ET rates are commonly estimated using potential or reference ET, which might differ actual rates. Actual evapotranspiration (ETa) can be Operational Simplified Surface Energy Balance (SSEBop) model. This report evaluates SSEBop ETa at point basin scales in Florida parts Alabama Georgia for 2000–17. computed data 24 micrometeorological stations referred to as mETa were used quantify biases rates, stratified generalized land-use type. Bias was minus given types, bias-correction equations least-squares regressions. In addition station locations, annual average calculated application a water-balance method 55 basins assess accuracy scale. Another independent model simulate based on monthly statewide daily (ETo) gridded dataset Geostationary Environmental Satellite estimates solar radiation (GOES ETo). grid points GOES ETo multiplied ratios ETo, each type.The coefficient determination (R2) between all combined improved 0.37 before bias correction 0.79 after individual land-uses R2 varied 0.59 type forest 0.82 shallow-water-table pasture. Root-mean-square error (RMSE) function difference RMSE 1.27 inches per month corrections 0.73 inch corrections. bias-corrected with complete years records ranged 2.01 year (in/yr) agriculture 5.73 in/yr deep water-table pasture, 4.96 21.21 percent errors relative respectively. Bias-corrected also compared (wbETa) Florida. Differences wbETa ?3.67 5.29 (?9.24 17.36 percent). when differences decreased, average, 4.13 uncorrected 1.95 The basins, 36.46 3.41 lower than rate 37.79 inches.Bias varies time step (monthly versus annual), scale (point, basin, statewide), Applications hydrologic models should consider inherent models. could calibration targets processes, such groundwater Annual introduced typically below margin associated typical residuals simulations, depending Surface-water groundwater-flow RMSEs order few feet benefit values ETa.