ESTAR- and model-derived multiscaling characteristics of soil moisture during SGP'97, Washita '92 and Washita '94

Abstract

Using a spatially distributed water and energy balance model, we investigate the spatial structure of surface fluxes and states for the Washita '92 field experiment and the August campaign of the Washita '94 field experiments. For Washita '92, the model is validated against gravimetric and remotely-sensed soil moisture, and for Washita '94, the model is validated against gravimetric soil moisture and measured energy fluxes. The model is shown to reasonably represent land-atmosphere interactions during the experimental periods. Scaling analysis of soil moisture and latent heat flux is indicative of multiscaling behavior. The multiscaling behavior of soil moisture and latent heat flux is hypothesized as a relationship that is a function of average soil moisture, and this relationship seems to fit the data quite well. Similar scaling analysis of important land surface properties indicates simple scaling for porosity, field capacity and leaf area index, and multiscaling for residual soil moisture and the soils-topographic index. This is consistent with model results, which indicate a transition from simple scaling to multiscaling with dry-down. It is hypothesized that this transition is governed by the scaling properties that in wet conditions control infiltration (porosity, field capacity, leaf area index) to properties that in dry conditions control drainage (residual moisture content and soils-topographic index).