The effect of soil hydraulic properties vs. soil texture in land surface models

Abstract

Proper selection of parameters for a land surface model is critical, but is difficult due to the lack of data and difficulties in scaling existing data. In particular, the spatial distribution of Soil Hydraulic Properties (SHPs) is not well known. This study focuses on the effect of SHP selection on modeled surface fluxes following a rain storm in a semi-arid environment. SHPs are often defined based on a Soil Texture Class (STC). To examine the effectiveness of this approach, we run the Noah land surface model with each of 1306 soils in a large SHP database. Within most STCs, the outputs have a range of 350 Wm-2 for latent and sensible heat fluxes, and 8K for surface temperature. The average difference between STC median values is only 100 Wm-2 for latent and sensible heat. STC explains 5-15% of the variance in model outputs and should not be used to determine SHPs. Copyright 2005 by the American Geophysical Union.