中国北西部砂漠における降雨特性

Abstract

Rainfall characteristics over the HEIFE area in the Northwestern China are investigated as an example of rainfall it the midlatitude arid area. Especially, its relations to the synoptic weather conditions are focused on. Results show that the rainfall within HEIFE area is mainly caused by the wave disturbances over polar front. Rainfall amount observed at the surface is revealed to be related linearly to the elevations of each station and decreased to 100 mm/year at the bottom of Hexi Corridor, 70% of which is occupied by desert.The possibility of rainfall is considered to be determined by the upper air conditions.During the summer, rainfall is sufficiently expected from the standpoint of water content and stability. But because of high lifting condensation level and mean downward air motion over the desert, rainfall is only possible when the large scale external forces like wave disturbances over polar front exist on this region. Meanwhile in winter, water content is quite small and stability shows nearly neutral.