广东2005年“3·22”强飑线天气过程分析

利用地面常规及自动气象站观测、NCEP/NCAR 1°×1°再分析资料和多普勒雷达探测等资料, 对2005年3月22日广东一次近年罕见的强飑线过程进行了天气动力学和中尺度的诊断分析, 对伴随飑线的强风暴区天气系统配置、空间结构特征及其演变特征等作了深入的探讨, 同时计算了强对流天气发生区域的有关物理量, 从中发现了一些有意义的事实, 以求为以后广东春季强对流天气的监测和预警提供一些有益的帮助。

Dynamic Diagnosis of an Infrequent Squall Line in Guangdong on March 22, 2005

A dynamic diagnosis and meso-scale analysis of an infrequent squall line on March 22,2005 in Guangdong is made using the routine observations,automatic weather station data,NCEP/NCAR reanalysis data and Doppler radar images.It's found that the squall line occurs under unstable stratification of environmental conditions and unstable physical mechanism,such as the trough at 500 hPa affecting the region where Guangdong borders Guangxi ahead of the trough at 700 hPa,so the acclivitous trough may be the dynamical trigger mechanism of the squall line's occurrence;the intrusion of the dry and cold air down from the upper troposphere affords the thermal instability field;the westerly jet is overlapped with the low southwest jet over the Guangdong and Guangxi,which brings the strong vertical wind shear,and the squall line develops strongly along the exit area of the low level jet after it is formed at the entrance of the upper jet above the low level jet;in the north and south of the squall line there are many new convection cells which keep building and tend to be combined towards the middle of the bow-shaped echo when the squall line grows;the squall line tends to have a dissymmetrical structure rather than a symmetrical structure when it weakens,and the comma head and tail of the squall line,which cause disasters,are still growing respectively;the echo's channel of weak reflectivity factor at the rear end of the bow-shaped echo,namely the mesosphere-influx mouth of trough,comes forth,which is a sign to the change when the squall line has turned to dissymmetrical structure from symmetrical structure,and the squall line develops to the most powerful stage;in this process it shows some features such as the bowshaped echo,the V-shaped mouth of trough,MARC and "long convection line" in front of the squall line.The strong inflow center,velocity convergence zone and small vortex velocity feature from the meridional velocity are also found.It is a good sign to identify the change of multi-cell storms that the long convection line of images occurs and develops all along the squall line;diagnostic analysis shows that the physical measures such as the vertical speed,wet static energy and CAPE can reflect effectively where the squall line has been born and where it has moved to.