一次夏季强沙尘暴形成机理的综合分析

Comprehensive Researches on a Special Dust Storm in Summer

利用沙尘暴发生前夕酒泉基准站的探空资料、沙尘暴发生前后地面自动站观测资料和有关台站的常规观测资料对2004年7月12日出现在我国内蒙古西部和河西走廊西端的一次沙尘暴天气过程,从大气层结稳定度、地形因素对沙尘暴影响的机理以及下垫面性质等方面进行了分析,并对天气现象发生时地面气象要素和地温的变化进行了研究。结果表明:①大气层结的不稳定起了激发作用;②该地区特殊的地形条件所造成的“狭管效应”起到了加强作用;③沙尘暴爆发前风速迅速增大,为起沙提供了动力条件;④气压和相对湿度在沙尘暴发生前夕和沙尘暴过程的中后期有明显扰动,沙尘暴结束后温度、气压、相对湿度和地面等气象要素有显著性突变。

According to the upper-air sounding radar data before sandstorm breaking out, the automatic meteorological observing data during sandstorm process in Jiuquan base station and the conventional observing data in other stations, we analyzed a case of weather events occurred in the west Mongolia and Jiuquan area of Gansu Province on July 12th, 2004. The stability of atmosphere, the mechanism of local terrain influencing sandstorm, and the characters of underlying Earth surface, as well as the variations of ground meteorological elements and ground temperature in event process have been studied, The result showed that （1） the instable atmospheric stratification played triggering role, （2） the ＂canalization＂ resulted from the special local terrain made intensifying action, （3） the rapidly increasing wind provided favorable dynamical condition. The atmospheric pressure and relative humidity obviously fluctuated in the prophase, the midterm and the later stages of sandstorm, further more, the ground surface metrological elements such as atmospheric temperature and pressure, relative humidity and underlying surface characters had abruptly changed after the event.