Characteristics of Hydrologic Transfer between Soil and Atmosphere over Gobi near Oasis at the End of Summer

By utilizing the data observed at Dunhuang during August and September 2000 in the "Field Experi-ment on Interaction between Land and Atmosphere in the Arid Region of Northwest China (FEILARNC)",the characteristics of the soil moisture, temperature, and atmospheric humidity are analyzed. It is foundthat the thickness of the soil temperature active layer is about 5 cm and much thinner than is typical,that not only the atmospheric humidity gradient is often inverted but also the soil moisture gradient inthe shallow layer in the Gobi near oasis, that the diurnal variation of soil moisture can be divided into thefour stages that are called the wet stage, the losing-water stage, the dry stage, and the attaining-waterstage. It is shown that in soil moisture profiles, the depth of the soil moisture active layer is about 10 cmand soil moisture inversion is the main feature in the shallow layer during the wet stage. Such a featureas soil moisture inversion indicates that soil in the shallow layer can inhale moisture from the air throughcondensation in the nighttime and exhale moisture to the air through evaporation in the daytime. Thecondensation and evaporation constitute together the full respiration process of moisture on the ground.The formation of soil moisture inversion is related with the state of soil temperature and moisture, theintensity of atmospheric humidity inversion, and the atmospheric thermodynamic stability.