A simple method for estimating the rate of evaporation from a dry sand surface.

Abstract

The authors' model of a dry surface layer of sand predicts that the upward vapor flux in the dry surface layer, or the rate of evaporation from the dry sand surface is not affected by the temperature gradient developed in the surface layer if the gradient is not too steep (Kobayashi et al., 1987).To verify this prediction, a simple laboratory experiment was conducted. Although the temperature gradient in a sandy field grows to be more than 5Kcm-1 on a clear day in high summer, we could make it develop only up to about 3Kcm-1 in this experiment. However, at least under the present experimental conditions, the above prediction could be corroborated.Thus, the present model gives us a simple method for estimating the rate of evaporation from a dry sand surface, which demands only a knowledge of the surface temperature and water content, and the thickness of the dry surface layer. In a sand dune field, there always the dry surface layer exists except during a short period immediately following a rainfall or irrigation; thus this method may be effective in investigating the water budget in a sandy field.