四川省两次区域性寒潮天气过程对比分析

Comparative Analysis of Two Regional Cold Wave Synoptic Process in Sichuan

本文利用NCEP 1°×1°逐6小时再分析资料和实况观测资料,运用天气分析和物理量诊断的方法,对四川省两次冬季区域性寒潮天气过程进行了对比分析,结果表明:(1)两次过程均属于中亚横槽型寒潮(N型),前期欧亚中高纬度地区环流径向度加大,乌拉尔山阻高强烈发展,后期横槽转竖东移引导冷空气南下,南下冷空气与南支槽前西南气流交汇入侵四川盆地,造成寒潮过程;(2)过程发生前,盆地大部地区基础温度较历史同期偏高,利于气温进一步下降;(3)西南急流能够将水汽不断向盆地内输送,连续的降水对气温下降起到了加强作用,是造成强降温的原因之一;(4)850hPa强冷平流是寒潮过程的关键因素,冷平流的移动路径和强度中心与过程降温地区有很好的对应。

Using the NCEP 1°×1°6 h reanalysis data and observation data,this paper research the synoptic characteristics of the two regional cold wave events by synoptic principle and dynamic diagnosis in Sichuan.The results showed that:(1)the two process are the type of Central Asia transversal trough cold wave(N-type),In the early stage,meridional circulation strengthens at the middle and high latitudes,explosively development of Ural blocking high,the cold air behind trough and the warm air before Southern Branch Trough meet over Sichuan Basin,causing the cold wave synoptic process.(2)Two cold wave synoptic process occurred with higher-than-normal temperature before the process,help the falling of temperature.(3)The southwest lower-level jet,which transports moisture to the Sichuan Basin,continuous precipitation is one of the causes of strong cooling.(4)The cold advection from 850 hPa is the key factor of the cold wave,there is a good correspondence between the mobile path and intensity center of cold advection and the process cooling area.