一次山东半岛强冷流暴雪过程的数值模拟和诊断分析

Numerical Simulation and Diagnostic Analysis of a Cold Airflow Snowstorm Process in Shandong Peninsula

利用NCEP/NCAR再分析资料,应用WRF中尺度数值模式对山东半岛2008年12月4—6日的冷流暴雪天气过程进行了数值模拟,利用模式输出的时空分辨率较高的资料,对此次冷流暴雪的特征及其产生的物理机制进行了分析。结果表明,这次暴雪产生在西北气流、较大海气温差的背景条件下,一定的海气温差是冷流暴雪的重要指标;冷流暴雪产生在较强垂直上升运动区的相当位温高值区附近;水汽输送方向为西北—东南向,水汽辐合层比较浅薄且范围狭窄;降雪分布具有明显的南少北多的特征;850 hPa湿Q矢量散度场辐合区的存在、位置及强度与暴雪的产生、落区及强度具有较好的对应关系;湿Q矢量分量的垂直分布揭示了次级环流的方向和强弱,暴雪位于次级环流的上升支附近。

Based on the NCEP/NCAR reanalysis data,the mesoscale model-WRF（Weather Research Forecast） is used to simulate the process of a cold-air snowstorm which occurred in Shandong Peninsula from December 4th to December 6th 2008.High spatio-temporal resolution data from model output are used to analyze the cold-air snowstorm process.Main conclusions are as follows：this snowstorm occurred under the background of the northwest airflow and significant sea-air temperature differences,which were an important symbol of cold airflow snowstorm.Snowstorm occurs in the high energy belt with strong ascending motion.The direction of vapor is NW-SE oriented and the convergence of vapor only occurs in middle-low layer and in a narrow region.Snowstorm is mainly distributed in the northern area of Shandong Peninsula.The existence,location and intensity of the convergence of wet-Q-vector at 850 hPa have a significant relationship with the emergence,distribution and strength of the snowstorm.Results also show that snowstorm occurs near the ascending branch of a secondary circulation,whose intensity and direction can be indicated by vertical distribution of wet-Q-vector.The above conclusions are beneficial for the snowstorm forecast in Shandong Peninsula.