A comparative analysis of two land surface heterogeneity representations

Abstract Two contrasting representations of land surface variability used in general circulation models (GCMS) are compared through an analysis of their corresponding surface energy balance equations. In one representation (the “mixture” approach), different vegetation types are assumed to be homogeneously mixed over a grid square, so that the GCM atmosphere sees near-surface conditions pertaining to the mixture only. In the second representation (the “mosaic” approach), different vegetation types are viewed as separate “tiles” of a grid-square “mosaic,” and each tile interacts with the atmosphere independently. The mosaic approach is computationally simpler and in many ways more flexible than the mixture approach. Analytical solutions to the linearized energy balance equations and numerical solutions to the nonlinear equations both demonstrate that the mixture strategy, when applied to two coexisting vegetation types that differ only in canopy transpiration resistance, promotes both total turbulent flux ...