HR: 11:20h
AN: H12A-05    [Abstracts]
TI: On the Selection of Soil Hydraulic Properties in Land Surface Models Based on Soil Texture
AU: * Gutmann, E D
EM: gutmann@colorado.edu
AF: University of Colorado, Boulder, Department of Geology Campus Box 399 2200 Colorado Ave., Boulder, CO 80309-0399 United States
AU: Small, E E
EM: Eric.Small@colorado.edu
AF: University of Colorado, Boulder, Department of Geology Campus Box 399 2200 Colorado Ave., Boulder, CO 80309-0399 United States
AB: One of the largest problems facing land surface modelers today is the lack of adequate parameter estimates. In particular, there is a lack of solid information on the spatial distribution of Soil Hydraulic Properties (SHPs). This study focuses on the effect of SHP selection on model outputs. We focus on modeled surface fluxes following a typical rain storm in a semi-arid environment. SHPs are often defined based on a soil texture classification, but soil texture class alone does not adequately specify SHPs. We show that a land surface model run with the range of SHPs from a large soils database produces more variability within a soil texture class than between classes. We take 1306 soils from the SHP database of Schaap and Leij (1998) and run the Noah land surface model with each soil. The only soil texture class which appears distinct is the sand class, and even for sands there is significant overlap with all other classes. Within most soil texture classes, the outputs have a range of 400$\frac{W}{m^2}$ for latent and sensible heat fluxes, 60$\frac{W}{m^2}$ for ground heat flux, and a range of almost 10K in surface temperature, in contrast the average difference between mean values of different soil texture classes is only 50$\frac{W}{m^2}$ for latent and sensible heat. With the exception of extremely sandy soils, the use of soil texture class as a predictor variable explains only 5% of the variance in model outputs, thus soil texture class should not be used to determine SHPs for land surface modeling.
DE: 1818 Evapotranspiration
DE: 1833 Hydroclimatology
DE: 1875 Unsaturated zone
DE: 1878 Water/energy interactions
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting