INFLUENCE OF SOIL-MOISTURE ON SIMULATIONS OF KATABATIC FLOW

Simulations of katabatic flow with a two-dimensional dynamic numerical model with a soil parameterization indicate that downslope flow developed over a moist slope is weaker than that over a dry slope. This agrees with earlier findings that daytime anabatic (upslope) flow is weaker over a moister slope. But, whereas the weaker anabatic flow is produced because surface evaporation prevents the moist slope from heating as much as a dry slope, the weaker katabatic flow is produced over moist slopes because (1) the soil thermal conductivity is greater in moist soil, and (2) downward longwave radiation flux From the atmosphere to the surface is greater because of higher humidity in the air near the surface from evaporation. The higher thermal conductivity allows warmer soil temperatures (heat) to diffuse upward to the soil surface and prevents the surface temperature from becoming as cold in the moist run as in the dry run.