Water Vapor Exchange between Soil and Atmosphere over a Gobi Surface near an Oasis in the Summer

Abstract

Abstract Using data observed at Dunhuang, in the Gansu, in the arid region of northwest China in the summer, the characteristics of the soil water content, temperature, and atmospheric humidity were analyzed. It was found that the depth of the active soil temperature layer is about 5 cm, which is much thinner than that of typical soils. In addition, not only is the atmospheric humidity gradient in the surface layer often inverted, but so too is the soil water content gradient in the shallow layer. The diurnal variation of soil water content can be divided into four stages, including wet, water loss, dry, and water gain. It is shown that in soil water content profiles the depth of the active soil layer is about 10 cm, and soil water content inversion is the primary feature in the shallow layer during the “wet” stage. The presence of soil water content inversion indicates that soil in the shallow layer can absorb water from the air through condensation in the nighttime and emit water vapor to the air through evaporation in the daytime. The formation of a soil water content inversion is mainly related to the state of the soil surface temperature.