Estimation of Surface Soil Water Content of Sand Dune at Night

Abstract

It is well known that soil water content at the surface of sand increases at night, which is dry in the daytime. The mechanism of this phenomenon, however has not quantitatively clarified because continuous measurement of nighttime soil water content is very difficult. Thus, in this study, the method to estimate nighttime surface soil water content was examined by using the meteorological and soil physical data measured at Tottori sand dune in 1995. Albedo of the infrared radiation and thermal conductivity of the sand surface, which are readily calculable, were selected as the parameters of the estimation equation. Albedoes can calculate from the surface temperatures of sand measured by thermocouple and radiation thermometer, and sky temperature measured by radiation thermometer. Thermal conductivities can calculate from the radiation balance, heat balance, and temperature gradient at soil surface. The results show that thermal conductivities would give satisfying estimations of surface soil water content of sand surface.