关键词: 沙尘, 最大混合层厚度, 逆温层, 垂直风场, 民勤

Abstract: To better understand distribution and variation of atmospheric mixed layer (ML) thickness and the impact of the ML thickness on the sand-dust climate over Northwest China, the maximum ML thickness, inversion layer characteristics, vertical wind field and their impacts on sand-dust climate formation have been calculated and analyzed by utilizing the daily observed sounding data at 08:00 and 20:00, precipitation and maximum temperature data at Minqin from May to June during 2006—2008. The atmospheric boundary has an obvious diurnal variation, and the ML thickness is deeper, inversion layer is stronger and more in daytime than at night. The maximum ML thickness of sand-dust is about 2 600 m, which is between no rainfall and rainfall. The blowing sand events are mainly resulted from cold front, but sandstorm mainly resulted from strong wind disturbance in lower atmosphere and cold front above 500 m in upper atmosphere. There is an obvious wind disturbance near surface before sandstorm, and when sandstorm happen there is obvious cold air below 500 hPa, which is stronger in daytime. When the strong sandstorms with visibility less than 100 m happen there is strong wind and cold air at night.

Key words: sand-dust, maximum mixed layer thickness, inversion layer, vertical wind field, Minqin