大连地区一次春季暴雪个例分析

摘要

A snow-storm synoptic process happened during March 3th to 4th in 2012 in Dalian City was analyzed using NCEP reanalyzed data. The results showed the snow-storm synoptic processes were caused by large scale circulation background of tow troughs and one upper ridge.The main influence systems of this precipitation process were long-wave trough and surface inverted trough.In the early of stage of precipitation process,the Hetao inverted trough developed northward,warm wet air and cold air met in northeast,the updraft extended to upper troposphere.The vertical velocity was small with value about 0.05~0.10 Pa/s,the precipitation was mixed rain and snow,and temperature rose slightly.In the middle stage,northern branch cold air masses moved southwards.The jet at the middle-lower level provided vapors,coupling of two jets at the upper and lower levels led to increasing of vertical velocity,the max vertical velocity was 0.6 Pa/s,the snow-storm was triggered and the temperature decreased slightly.In the last stage,all levels were northwest air current,the stratification became stable and the snow-storm end gradually.%利用NCEP资料分析了2012年3月4-6日大连市一次暴雪过程。结果表明：这次暴雪发生在两槽一脊的大尺度环流背景下，高空长波槽和地面倒槽是这次降水的影响系统。降水前期，河套倒槽北上发展旺盛，暖湿气流与冷空气在东北交汇，气流上升区延伸至对流层高层，垂直上升速度较小，值为0.05~0.10 Pa/s，前期降水多表现为雨夹雪，气温略微上升。降水中期，北支冷空气南压，中低空西南急流不断提供水汽，高低空耦合的加强导致垂直上升速度加强，最大值0.6 Pa/s，触发暴雪，温度略有下降。降水末期，整个气层以西北气流为主，层结变得稳定，降雪趋于结束。