Studies with the Biosphere-Atmosphere Transfer Scheme 10-layer soil model

Offline simulations using the new Biosphere Atmosphere Transfer Scheme (BATS) 10-layer soil model are compared with those of standard 3-layer model on a global and local scale. The purpose of the new 10-layer soil model is to improve the ability to simulate soil water and soil temperature as a function of depth, as well as the movement of water and energy into and out of the system, in order to improve the modeling of surface-atmosphere processes (and ultimately the simulation of the global climate in general circulation models). Preliminary results show that the 10-layer soil model tends to have much drier soils in the driest regions (mean annual precipitation < 1.0 mm/day) and wetter soils in the wettest regions (mean annual precipitation > 4.0 mm/day) than does the 3-layer soil model; soil moisture in areas of moderate precipitation is similar in both models. Increases in runoff and bare soil evaporation and changes in sensible and latent heat fluxes can be attributed to specific precipitation regimes and combinations of vegetation and soil parameters. However, decreased transpiration and increase soil heat flux occurs globally for almost all points. Further sensitivity experiments with the 10-layer soil model will be discussed, as well as validation of the model results against observational data for specific regions.