2009年2月3日宁夏大雾天气过程分析

Analysis of heavy fog proces in Ningxia on February,3th,2009

利用自动气象站和T213数值预报产品资料,对2009年2月3日宁夏大部出现的大雾天气过程从高低空环流形势、物理量场及气象要素的变化等方面进行了分析.结果表明,亚欧大陆500 hPa中高纬度的环流形势为较平直的西风气流,中纬度无明显冷空气活动,南支气流较平直,天气形势比较稳定;地面宁夏位于华北高压后部,近地面层有弱的偏南风或偏东风是这次大雾天气生成的背景场.表征大气稳定度的K指数、θse等不仅是强对流等灾害性天气的预报指标,对大雾天气也有一定的指示意义.

Using the information of automatic weather stations and T213 numerical forecast products,a weather precoss of heavy fog occurrenced in most areas of Ningxia on on February,3th,2009 was analyzed from the high and low circulation,physical field and the changes of meteorological elements.Results shown： the circulation in the 500 hPa high of Eurasian continent was relatively flat westerlies,no obvious cold-air was in mid-latitude,the south branch was flat and the weather conditions was stable;on the ground,Ningxia is located behind the North China high-pressure,the background field of this fog weather process is the weak south wind and east wind near the ground.K index and pseudo-equivalent potential temperature which can characterize the atmospheric stability,are not only the forecast indicator of strong convectively severe weather,but also the instruction meaning of fog weather process.