2008年初江苏暴雪天气的诊断分析

用2008年1月25—29日NCEP/NCAR一日四次全球再分析资料对1月25—29日江苏省大范围强降雪过程的天气背景、散度场、水汽通量的流函数与势函数、视热源与视水汽汇以及Q矢量等物理量进行了分析,并进行了南北地区的对比。结果表明:(1)200 hPa与850 hPa的散度差值场,与降雪落区有较好的对应关系;(2)沿江和苏南地区明显的水汽辐合,配合北方冷空气的向南侵入,是造成江淮流域持续暴雪的重要原因之一;(3)强降雪期间,非绝热加热对降雪产生重要影响,其中淮河以南降雪以对流性降雪为主,淮河以北地区以非对流性降雪为主;(4)非地转风造成的Q矢量辐合区主要位于850 hPa切变线附近,为强降雪提供了有利条件。

Diagnostic analysis of heavy snow weather in Jiangsu province in winter of 2008

Using NCEP/NCAR reanalysis data during 25-29 Jan. 2008,we have analyzed the physical quantities including the circulations for weather background, divergence field, vertical velocity field, streamfunction along with the potential velocity of water vapor transport, and the Q vectors during the heavy snow process as observed in Jiangsu province. The comparison of features of those physical quantities in southern part of Jiangsu, where the snow center is located, with those in the northern part of Jiangsu has been made. Our results have demonstrated that the falling area of snow can be identified well by the positive value of differences of the divergence of wind at 200 hPa with that at 850 hPa, which is meaningful for us to predict the place where the snowstorm will occur. The significant moisture convergence, along with the anomalies of cold air that appear around Yangtze River and southern of Jiangsu, is one of the important factors determining the continuous heavy snowfall over the Yangtze-Huaihe Valley. The Q vector convergence area caused by ageostrophic wind which is located in shear line at 850 hPa possibly provide a favorable condition for this heavy snowfall process.