A soil-vegetation-atmosphere transfer scheme for modeling spatially variable water and energy balance processes

In support of the eventual goal to integrate remotely sensed observations with coupled land-atmosphere models, a soil-vegetation-atmosphere transfer scheme is presented which can represent spatially variable water and energy balance processes on timescales of minutes to months. This scheme differs from previous schemes developed to address similar objectives in that it: (1) represents horizontal heterogeneity and transport in a TOPMODEL framework, and (2) maintains computational efficiency while representing the processes most important for our applications. The model is based on the original TOPMODEL-based land surface-atmosphere transfer scheme [Famiglietti and Wood, 1994a] with modifications to correct for deficiencies in the representation of ground heat flux, soil column geometry, soil evaporation, transpiration, and the effect of atmospheric stability on energy fluxes. These deficiencies were found to cause errors in the model predictions in quantities such as the sensible heat flux, to which the development of the atmospheric boundary layer is particularly sensitive. Application of the model to the entire First International Satellite Land Surface Climatology Project Field Experiment 1987 experimental period, focusing on Intensive Field Campaigns 3 and 4, shows that it successfully represents the essential processes of interest.