Linear models for estimating annual and growing season reference evapotranspirationLinear regression equations to estimate location-specific average annual reference evapotranspiration (ETo) were developed using one or more of annual averages of: incoming solar radiation (Rs), air temperature (T), relative humidity (RH), and wind speed (U). We additionally provide two sets of equations to estimate growing season ETo.
Spatial patterns of annual ETo and growing season ETo across the contiguous United States were estimated using existing spatial datasets of annual averages of Rs, T , RH, and U. Other applications of the models provided may include rapid assessments of historical annual and growing season ETo, evaluation of past ETo trends, or evaluation of ETo projected trends based on output from global climate models. More... |
Revised coefficients for radiation-based equations for estimating daily reference evapotranspirationMany applications require estimation of reference evapotranspiration (ETo) in areas where meteorological measurements are limited. Previous studies have shown that simple evapotranspiration models based on radiation and temperature perform relatively well in humid climates but underpredict ETo in drier and windier climates.
Equations for adjusting the model coefficients were developed based on annual averages of relative humidity RH [or vapor pressure deficit (VPD)] and wind speed U to improve the performance of these models for drier and windier sites. Publicly available data sets of spatial distributions of annual RH and U were used to estimate local coefficients for the contiguous United States. The revised coefficients can be used to improve estimation of reference ETo in data-limited applications such as remote sensing and distributed hydrologic modeling. More... |