Daily Reference Evapotranspiration (RET) and Potential Evapotranspiration (PET) over Florida, 1985 to 1995, and 2015

Potential (PET) and reference (RET) evapotranspiration are computed at 2-kilometer, daily resolution throughout Florida as part of a long-term multiagency partnership between the U.S. Geological Survey and all 5 Water Managements Districts in Florida. In 2015, a pilot study was initiated to historically extend (1985 to 1995) this database and potentially improve calculations with (1) albedos measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) and (2) forecasts of air temperature, relative humidity and wind speed from climate models such as North American Regional Reanalysis (NARR) simulations. During the pilot study, experiments revealed that radial-basis functions created superior regional distributions of air temperature, relative humidity and wind speed data over Florida, in contrast with inverse-distance interpolation that was plagued with "bulls-eye" effects. Due to sparse historical weather station data, NARR simulation results were used with radial-basis interpolation to historically extend the database from 1985 to 1995, for better characterization of the long-term variability in PET and RET. In summary, the pilot study improved some data sources, while revealing previously unknown variability in PET and RET created by the "covered karst" terrain of central Florida, urbanization, and flooding events in regional wetlands such as the subtropical south Florida Everglades.