A Statistical–Dynamical Parameterization of Interception and Land Surface–Atmosphere Interactions

Abstract

At a local scale, the interception capacity of the canopy depends on a variety of climatic and canopy factors. Of particular importance is the intensity of rainfall?interception capacity varies inversely with rainfall intensity. At a field or regional scale, like the scale of global climate models, the spatially averaged interception also depends significantly on the spatial variability of rainfall intensity and total precipitation depth. A new parameterization of canopy interception is developed. In the new parameterization, the spatial average of actual interception is obtained as a function of rainfall intensity and total precipitation depth, and of an interception capacity, which depends on the characteristics of the leaf surface and of the vegetation cover. In a statistical?dynamical framework, the new parameterization also accounts for the subgrid-scale spatial variability of rainfall intensity and total precipitation depth. The implications of accounting for the dependence of interception capacity on rainfall characteristics are examined by assessing the consequent responses of the energy and the water fluxes at the land surface. This is accomplished by incorporating the new parameterization into a soil?plant?atmosphere column model that is fundamentally based on the physical parameterizations of NCAR?s Community Climate Model.