Upscaling of Coupled Land Surface Process Modeling for Heterogeneous Landscapes: Stochastic Approach

Abstract

Land surfaces are spatially inhomogeneous at the spatial scales of vegetation canopies to watersheds or even continents. The spatial heterogeneity strongly affects heat, momentum, and vapor exchange at the land surface. It is necessary to consider the spatial heterogeneity of land surface properties in the land surface process modeling that is required for regional hydroclimate models. The main objective of this study is to develop a stochastic upscaling methodology for land surface process modeling for heterogeneous landscapes. Fokker-Planck equation (FPE) as a probabilistic model for land surface processes is formulated in a one-dimensional probability domain for land surface temperature. The numerical solutions of the FPE are validated by Monte Carlo simulations. The validation results are quite encouraging and point toward potential use of this model as a land surface hydrologic model for the two-way nonlinear coupling with a regional atmospheric model to represent the subgrid variability of the land surface processes. Furthermore, in this study, a sensitivity analysis using the FPE was performed to investigate the sensitivity of the spatial variability of land surface temperature to the variance of land surface parameters.