The Origin of Soil Moisture Evaporation "Regimes"

Abstract

Evaporation plays an extremely important role in determining summertime surface temperature and surface temperature variability over land. Observations show the relationship between evaporation and soil moisture generally conforms to the Budyko (1961) We have developed the Simple Land Atmosphere Model (SLAM) as a tool for studying land atmosphere interaction in general, and summertime temperature variability in particular. We use the SLAM to show that a negative feedback between evaporation and surface temperature gives rise to the two apparent evaporation ``regimes" without complex parameterizations. Stemming from vapor pressure deficit's temperature dependence, the feedback we identify has important implications for how transitions between wet and dry climates may impact temperature variability as the climate warms. We also elucidate the impacts of surface moisture and insolation perturbations on latent and sensible heat fluxes and on surface temperature variability.