针对2008年初发生在贵州地区的严重冻雨过程, 分别从环流背景、低空急流和水汽输送条件等方面分析了准静止锋维持的原因, 并选取本次灾害最严重的第3次过程为典型个例, 利用WRF模式针对准静止锋影响下的贵州冻雨进行数值模拟来研究冻雨的发生机制。模拟结果较好地反映出高低空环流形势场特征, 强雨雪降水带的走向、落区, 以及地面温度的分布, 均与观测基本吻合。通过分析高分辨率模式的模拟结果, 揭示了准静止锋上贵州地区冻雨的层结结构特征及云物质在冻雨区的分布特征。研究结果表明, 贵州中部的冻雨区除一般的三层结构(包含冰晶层、暖层和冷层)外, 还具有典型的两层结构特征, 即: 高空的固体降水粒子稀少, 900~600 hPa深厚的逆温层和0℃以上的暖层使中低空存在大量液态粒子, 下落的液滴经过近地面的浅薄冷层, 形成大量过冷却雨滴, 而后降落至地面迅速冻结。
Severe freezing rain disaster has happened in Guizhou Province early 2008. The meso-scale maintenance mechanism of the stationary front related to the event is analyzed from the aspects of circulation, lower jet and moisture transportation. And as typical case, the third process which is the most devastating one in the event has been simulated through WRF model. The results consist with observations in circulation pattern, precipitation distribution and intensity. High resolution simulation clearly reflects stratification structure of stationary front and distribution characteristics of cloud substances over freezing rain area in Guizhou. The research shows that except the general three-layer structure (includes ice layer, warm layer and cold layer), the typical two-layer structure of freezing rain also appeared in central region of Guizhou. This means freezing rain may develop merely when a deep warm moist layer that has temperature exceed 0℃ in middle altitude overruns a colder layer, while solid particles in upper air hardly exist. Abundant liquid drops contain in warm layer fall through shallow colder layer forming supercooling raindrops, and freeze on contact with surface.
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