“1998年二度梅”暴雨与非线性亚临界对称不稳定的初步研究  

Primary Study on Nonlinear Subcritical Symmetric Instability and the Second Meiyu Rainstorm in 1998

作　　者：夏瑛[1] 陆维松[1] 

机构地区：[1]南京信息工程大学大气科学系,江苏南京210044

出　　处：《南京气象学院学报》2004年第5期595-605,共11页Journal of Nanjing Institute of Meteorology

基　　金：国家自然科学基金资助项目(40275061);国家重点基础研究发展规划项目(G1998040907)

摘　　要：对1998年7月20日00时—8月1日12时这段梅雨暴雨过程进行诊断分析,并利用MM5V3中尺度模式作梅雨暴雨的数值试验,结果表明:(1)本次梅雨暴雨分为3大段过程,非线性亚临界对称不稳定可能是3段梅雨暴雨形成的重要机制;(2)扰动风场增长与降水增长关系密切,扰动风场的增长会超前于降水的增长,非线性亚临界对称不稳定的增强可能使降水增强;(3)非线性亚临界对称不稳定主要发生在高层200hPa,中层500hPa也有发生。非线性亚临界对称不稳定使线性对称稳定的大气变为不稳定。降水区和暴雨中心主要位于高层200hPa和中层500hPa扰动风场极大值南侧与低层850hPa扰动风场极大值北侧之间。(4)非线性亚临界对称不稳定扰动的e折时间和空间尺度,分别为5～8h和200～300km。Diagnostic analyses are carried out for the Meiyu rainstorm in the Meiyu period from 0000UTC 20th July to 1200UTC 1st August in 1998 and the MM5V3 meso-scale model is used to simulate the Meiyu rainstorm.The results show that (1)this precipitation process can be divided into three periods and the nonlinear subcritical symmetric instability is the main mechanism;(2)the increase of rainfall has a close relation with the increase of the disturbance wind which can often be found before the increase of rainfall,so the increase of the nonlinear subcritical symmetric instability can make the rainfall increase;(3) the nonlinear subcritical symmetric instability mainly occurs at 200hPa and 500hPa which can make the atmosphere from linear symmetric stability to instability.Heavy precipitation mainly occurs at the place between the south side of the maximum disturbance wind field at high or middle levels(200hPa or 500hPa)and the north side of the maximum disturbance wind field at the low level(850hPa);(4) The e-folding temporal and spatial scales of the nonlinear subcritical symmetric instability disturbance are respectively 5～8h and 200～300km.

关 键 词：亚临界对称不稳定 非线性 梅雨暴雨 

分 类 号：P458.121.1[天文地球—大气科学及气象学]