OASIS-EFFECT OBSERVED AT ZHANGYE OASIS IN THE HEXI CORRIDOR, CHINA

The surface energy balance at the Zhangye Oasis during June 1991 was c alculated from the fundamental observation period (FOP) data of the He ihe River Basin Field Experiment (HEIFE). Typical phenomena induced by the oasis effect were observed during the afternoons on fair weather days in June. An inversion layer over the oasis developed from the sur face to 8 m height in the afternoon when the wind speed was strong. Th e temperature difference between 1-8 m heights was about 2 degrees C. The specific humidity exhibited a steep vertical gradient over the oas is. The latent heat flux was the dominant term in the surface energy b alance. The sensible heat flux was small and upward during the morning hours, but was directed downward in the afternoon due to large evapor ative heat loss. On the contrary, the sensible heat flux was the domin ant term at the desert station. The net radiation in the daytime was s mall and only 63% of that at the oasis. A model of the observed oasis effect is proposed in the present note.