廊坊市回流型强降雪天气及预报指标分析

统计了1990-2009年间降雪资料的基础上，运用历史天气图、micaps资料以及NCEP再分析资料，对回流型强降雪个例进行了详细分析，总结了华北回流型强降雪天气的普遍特征，通过对回流形势和廊坊及上游沿线测站高低空物理量特征的诊断分析，归纳出一些适合廊坊本地的预报指标，并通过初级模型的建立进一步提高当地强降雪预报的准确率。结果表明：回流降雪过程500 hPa高空形势可分为两类：两槽一脊型和多波动型；地面图上亚欧东部基本呈“北高南低”或“东北高西南低”的形势，高压中心的平均强度可达1045.5 hPa。廊坊地面风的上游即渤海西岸为显著的北到东风，当风速达到5 m·s^-1以上时要注意强降雪的发生。

Analysis of backflow heavy snowfall weather and its prediction index in Langfang

On the basis of snowfall data from 1990 to 2009 ,the weather chart,the MICAPS data and the NCEP re- analysis data,backflow heavy snowfall cases in the North China were analyzed and its basic characteristics were summarized. The situation of backflow heavy snowfall and physical features in upper and lower levels at Langfang station and its upstream stations were diagnosed, and some forecast indexes were selected. The results show that the 500 hPa circulation and ground patterns can be respectively divided into two types, i. e. the two troughs and one ridge type and the multi-wave type. It appears ＂high north and low south＂ or ＂northeast high and southwest low＂ in the east of Asia-Europe on the ground map. The mean intensity at the center of high pressure reaches 1045.5 hPa. The upstream wind direction of ground wind along Langfang is north to East, namely in the west coast of the Bohai sea. The heavy snowfall will happen when the wind speed exceeds 5.0 m·s^-1.