AN APPROACH FOR THE REPRESENTATION OF SURFACE HETEROGENEITY IN LAND-SURFACE MODELS .2. VALIDATION AND SENSITIVITY EXPERIMENTS

This paper discusses a series of sensitivity experiments aimed at test ing the surface heterogeneity representation proposed in the companion paper by Giorgi. When driven by observed climatic forcings at three l ocations and run in point mode, the model shows good performance in re producing observed surface fluxes; The temperature heterogeneity repre sentation mostly affects the process of snow formation and, therefore, the winter and spring energy and water budgets. The soil water hetero geneity primarily influences the processes of soil water movement and runoff generation, thereby modifying the surface hydrologic budget. In addition, the heterogeneous model results compare reasonably well wit h aggregated results from point-mode experiments. Model sensitivity to the presence of impermeable surface fractional cover, fractional prec ipitation area, and a crude delayed runoff formulation is also discuss ed. As a next phase of model evaluation, it is planned to include this heterogeneity representation within a regional climate model and asse ss its effect on atmospheric circulations.