Diurnal Change of Soil Temperature and Evaporation through Dry Layer in Tsukuba Kanto Loam

Relationship between Diurnal Change of Soil Temperature and Soil Water Content in a Bare Field (I)

Abstract

Diurnal soil temperature fluctuation, water content and soil water potential profiles, evaporation rate, and radiation were measured in a bare field in Tsukuba, to investigate the wet and dry effects of surface soil on soil temperature. When a dry soil layer appeared at surface, the surface temperature amplitude increased significantly, but the amplitude in the wet layer beneath the dry layer was similar to that without the dry layer. The reasons were found that the dry layer has high resistance to heat flow, and the location of heat sink due to latent heat of evaporation shifts down to the bottom of the dry layer, while evaporation rate is reduced by the dry layer. Measured relative humidity profile in the soil showed that evaporation rate is restricted by vapor diffusion in the dry layer.