“7·12”特异沙尘暴成因研究

Study on the Formation Causes of the Peculiar Dust Storm Occurred on July 12, 2004

2004年7月12日在我国内蒙古西部和河西走廊西端出现了一次特异沙尘暴天气过程,根据造成这次沙尘暴的天气形势确定了触发机制,用能量天气学方法和温度对数压力图对大气层结稳定度进行了描述,从层结与地形因素影响沙尘暴的机理及下垫面性质等角度进行分析研究。结果表明,高空切变线和大气层结不稳定的共同作用是导致这次沙尘暴的主要因素;该地区特殊的地形条件所形成的“狭管效应”,对沙尘暴天气现象起到了加强作用。

The study area, the Jiuquan region, is located in the west of the Hexi Corridor, Gansu Province, the Taklimakan Desert （the largest sand desert in China） and the Kumtag Desert are located on its western side, the Mazong Mountain, Badanjilin Desert and Qilian Mountain are located on its northern, eastern and southern sides respectively, and some large Gobi deserts are distributed in the Jiuquan region. It belongs to the typical temperate arid continental climate, the precipitation is less but the evaporation is very high. Except some oasis pieces are distributed along the continental rivers, Gobi deserts are dominant in the Jiuquan region, and the sand deserts are dominant in the Andun Basin. These Gobi and sand deserts are the main sand-dust sources for the occurrence of dust storms in the Jiuquan region. Moreover, the farmlands with loose soil are also the sand-dust sources. In this paper, a peculiar dust storm occurred in west Inner Mongolia and the Jiuquan region in the Hexi Corridor of Gansu Province on July 12, 2004, is analyzed, the synoptic situation is used to determine the trigger mechanism of the dust storm, the energy synoptic meteorology and the emagrams are used to analyze the atmospheric stability, and the local conditions, special geographical location and features of the underlying surface affecting the occurrence of dust storms are analyzed. The results are as follows： （1） The Jiuquan region is one of the areas where dust storms occur frequently, however, such serious dust storm occurred on July 12, 2004, was seldom in history; （2） Most dust storms in the Jiuquan region are caused by the severe invasion of cold air current along northwest or west route, the dust storm occurred on July 12, 2004, however, was driven by east wind; （3） The unstable atmospheric layer affected jointly by the upper-air shear line and thermal action of underlying surface played an important role in the occurrence of the dust storm occurred on July 12, 2004; （4） The change of meteorological factors was advantageous for the occurrence of the dust storm occurred on July 12, 2004; （5） The “narrow-corridor effect” composed of the peculiar terrain and geographical location of Jiuquan also played an important role in occurring the dust storm on July 12, 2004.