Comparison of three land-surface schemes with the Fourier amplitude sensitivity test (FAST)

Abstract

This paper explores which are the land-surface parameters playing a key role in three surface schemes, namely the land-atmosphere interactive dynamics (LAID), the interaction soil-biosphere-atmosphere (ISBA) and the biosphere-atmosphere transfer scheme (BATS). The Fourier amplitude sensitivity test (FAST) was used for that purpose. This test estimates the relative contribution of model input parameters to the variance of surface heat fluxes. This analysis demonstrates that, for the three considered schemes, four parameters can explain most of the variance of surface heat fluxes under a broad range of environmental conditions. Soil wetness plays a predominant roˆ le for the heat fluxes. Roughness length is the most important parameter for the momentum flux. Leaf area index, in vegetated land, and texture, mainly in bare land, also have a significant impact on the fluxes. Roughness length is usually more important for sensible heat flux than for latent heat flux, and is mostly important under stable atmospheric conditions. Soil wetness and vegetation parameters are the dominant parameters under buoyant conditions.