Estimation of instantaneous, diurnal, and daily evaporative fraction using readily available inputs in the wetlands of South Florida, United States

Abstract

Evaporative fraction (EF) is the ratio of latent heat (LE in W m(-2)) to available energy at the land surface. It can aid in partitioning the Sun's energy available at the Earth's surface into surface energy fluxes to understand land-atmosphere interactions as well as monitoring Evapotranspiration and terrestrial drought conditions. In this study, the feasibility of estimating instantaneous, diurnal, and daily EF with minimal satellite and meteorological inputs based on the temperature difference-vegetation index framework is explored in South Florida, United States (US). The model performance is assessed against the ground observations collected at three flux stations between 2008 and 2011. It was found that the energy balance closure was improved by 9% at the long hydroperiod marsh site (i.e. US-Elm) and 6% at the short hydroperiod marsh site (i.e. US-Esm) after water heat storage (W) correction was applied on energy fluxes since W is more important than soil heat flux (G) for wetland ecosystems. The results further indicated that the model produced accurate EF estimates and performed the best on diurnal, then instantaneous, and lastly daily periods. Overall, the model can be used to produce spatially continuous EF and ET maps since the flux towers are no longer active.