重庆雾气候特征及天气成因分析

利用1980-2011年的重庆全市36个区县气象站的能见度及相对湿度资料，分析了重庆全区域雾的气候特征。选取全市的典型浓雾个例，利用NCEP 1°×1°的再分析资料和L波段雷达资料，合成分析了辐射雾和雨雾的环流形势、温、湿、风的垂直结构。结果表明：重庆全区域雾呈现西多东少的分布形势，出现的时间主要集中在10月至次年2月，年平均雾日数在21世纪初呈现显著下降趋势，雾日减少的突变发生在2002年。辐射雾发生时500 hPa中亚及青藏高原地区为高压脊，地面上重庆位于高气压内部的均压场中，冷锋已到达华南地区；而雨雾发生时500 hPa青藏高原地区为低压槽区，地面冷高压中心位于我国北方地区，有弱冷空气经大巴山从东北向渗入重庆。两种雾的温、湿、风垂直结构特征表现为辐射雾近地层逆温明显强于雨雾；上干下湿和湿层深厚分别是辐射雾和雨雾形成时，湿度垂直结构的主要特征；两种雾形成时近地层风速都很小，总体来看雨雾发生时各层的风速都大于辐射雾。

Climatic characteristics of fog and its forming reason in Chongqing

Based on the visibility and relative humidity data at 36 weather stations from 1980 to 2011 in Chongqing, the climatic characteristics of fog were analyzed. Typical heavy fog events were selected, and the circu- lation situation of radiation fog and rainy fog, vertical structure of temperature, humidity and wind were discussed using the NCEP reanalysis data with the resolution of 1°×1° and the L band radar data. The results indicate that the number of fog events is larger in the west than in the east of Chongqing, and the fog weather usually appears from October to February of next year. Annual mean number of fog days is in a significant decreasing trend in the early of this century, and an abrupt change occurs in 2002. There is high pressure ridge at 500 hPa in areas of Central A- sia and Qinghai-Tibet plateau when radiation fog takes place, and Chongqing is located in the pressure equalization field inside the high atmosphere pressure and cold front reaches the South China. However, there is low pressure trough at 500 hPa in Qinghai-Tibet plateau when rainy fog takes place, and the center of surface cold high pressure is located in the north of China, which makes the weak cold air penetrating through Daba Mountain into Chongqing from the northeast. The vertical structures of temperature, humidity and wind speed for fogs of two types differ each other. Inversion temperature of radiation fog near the ground layer is obviously stronger than that of rainy fog. The vertical structure of humidity for radiation fog is dry in the upper layer and wet in the lower layer, while that of rainy fog is deep wet layer. At the same time, wind speed near the ground is slow, while the wind speed in each layer is faster during rainy fog than during radiation fog.