江苏地区两次强飑线天气过程的特征分析

Characteristic analysis of two severe squall line processes in Jiangsu area

摘要:

利用常规观测资料、NCEP/NCAR再分析资料、自动气象站加密观测及多普勒雷达资料,对2006年4月28日和2009年6月14日发生在江苏及周边地区的两次典型飑线过程进行了对比分析。结果表明,两次过程发生前期,对流层低层伴有明显的暖平流,中高层出现冷平流,促进了该地区大气层结不稳定的形成和发展;在飑线移动发展过程中,地面风场中对应一条清晰的辐合线,对飑线的触发和维持起着重要的作用。两次过程中环境场的热动力结构存在明显差异:就热力条件而言,前者发生在春季,冷空气势力依然较强,对流层低层的暖平流是大气层结不稳定发展的主要原因之一,后者发生在暖湿气流相对活跃的夏季,中高层冷空气的侵袭更值得关注;动力条件分析表明,前者低层辐合抬升条件明显好于后者,而后者的热力条件占优势,一旦对流启动,更容易发展。

Abstract:

Based on the conventional observations,NECP/NCAR reanalysis data,automatic weather station intensive observations and Doppler radar data,this paper contrasts the two typical squall line processes in Jiangsu and its surrounding areas on 28 Apirl 2006 and 14 June 2009.Results show that,prior to the two squall line processes,the warm advection obviously occurs in the lower troposphere and the cold advection appears in the middle-upper troposphere,which is helpful for the formation and development of stratification instability.During the movement and development of squall lines,a clear convergence line occurs in the surface wind field,which plays an important role in the triggering and maintenance of the squall lines.There are obvious differences of thermal and dynamic structures between the environment fields of the two processes.For the thermal structures,the former happens in spring when cold air is still strong and warm advection in the lower troposphere is one of main reasons of stratification instability,and the latter happens in summer when warm moist air is active and cold air invasion in middle-upper troposphere deserves attention greatly.The dynamic analysis shows that low level convergence and lifting conditions of the former are better than those of the latter.However,the thermal conditions of the latter are predominant,and it is easier to develop once the convection starts.