Oasis Effect Observed at Zhangye Oasis in the Hexi Corridor, China

Abstract

The surface energy balance at the Zhangye Oasis during June 1991 was calculated from the fundamental observation period (FOP) data of the Heihe 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 surface to 8m height in the afternoon when the wind speed was strong. The temperature difference between 1-8m heights was about 2°C. The specific humidity exhibited a steep vertical gradient over the oasis. The latent heat flux was the dominant term in the surface energy balance. The sensible heat flux was small and upward during the morning hours, but was directed downward in the afternoon due to large evaporative heat loss.
On the contrary, the sensible heat flux was the dominant term at the desert station. The net radiation in the daytime was small and only 63% of that at the oasis.
A model of the observed oasis effect is proposed in the present note.