西北地区一次大范围沙尘天气环流动力特征分析

The Circulation Dynamical Structure of a Severe Dust Storm Process in Northwest China

根据常规观测资料和美国NCEP/NCAR提供的1°×1°6 h再分析资料,对2006年4月9—11日我国西北地区大范围沙尘天气过程环流动力特征等进行了分析。结果表明,高空急流、相对涡度和垂直速度在沙尘暴发生发展的不同时期有着较好的配置,沙尘暴发展的强盛期,相对涡度和垂直速度的不对称结构亦较强,在高空急流中心下方存在一个北部上升南部下沉的反环流,沙尘暴主要发生在高空急流中心南侧37°—44°N范围内,即在反环流区域的下沉气流区和热低压北部上升气流区。

The observed data and the NCEP/NCAR I°× 1°6-hour reanalysis data were used to analyze the circulation dynamical structure of dust storm processes during April 9--11, 2006 in Northwest China. The results show that upper jet flow, relative vorticity, pressure vertical velocity differently matched in various periods of dust storm development, and their values and spatial distributions were well-corresponding to the forming, developing and decaying of dust event. In strong stage of dust storm, the asymmetric structure of relative vorticity was enhanced. There was a couter-circulation at the lower side of the centre of the upper jet flow, and dust storms mainly occurred in the area of 37° N to 44° N, just the downdraught region of the couter-circulation.