辽宁初夏降水大尺度环流影响因子及2012年初夏异常多雨成因分析

Large-Scale Circulation Factors of Early Summer Precipitation in Liaoning Province and Causes Analysis of Heavy Precipitation in 2012

利用辽宁省50站1961—2012年夏季逐日降水资料及NCEP/NCAR逐日再分析资料,对辽宁初夏降水异常的大尺度环流特征进行了诊断分析。在此基础上对引起2012年辽宁初夏降水异常偏多的大尺度环流进行了研究。研究发现:东亚地区对流层不同高度上大尺度环流系统相互配合是造成辽宁初夏降水异常的主要原因。2012年辽宁初夏的4次主要降水过程对应的环流形势基本相同,200 hPa高空急流在东北以西上空出现气旋式分支现象;500 hPa上亚洲中纬地区受两槽两脊控制,东北地区上空是槽区,对应明显的位势高度负距平;850 hPa风场和整层水汽通量场上,东北地区上空均为气旋式环流;多雨年200 hPa高空急流出现分支现象,副热带西风急流强度偏强;500 hPa亚洲中纬地区受两脊一槽控制,东北地区上空是槽区,对应位势高度负距平;850 hPa风场在东北地区上空表现为气旋式环流。这表明东北地区上空对流层从低到高,都受一个深厚的低值系统控制;各层环流情况均表明:东北冷涡这一深厚的冷性涡旋系统是2012年辽宁初夏降水异常偏多的主要影响因子。

Based on the daily rainfall data of 50 observational stations in Liaoning Province during 1961-2012,and NCEP/NCAR daily reanalysis data,the large-scale circulation characteristics of Liaoning rainfall and the causes of heavy precipitation during early summer in 2012 were analyzed.The results show that the cooperation of large-scale circulation system in different heights of troposphere in East Asia is the main cause for precipitation anomaly in Liaoning in early summer.The circulation features of the four main precipitation processes in Liaoning in early summer are almost the same.Upper-level jet stream shows the phenomenon of branch at 200 hPa over the west of Northeast.Two ridges and two troughs control Asia mid-latitude regions at 500 hPa,and one trough controls the Northeast,corresponding to negative geopotential height anomaly.850 hPa wind field and the 1000--300 hPa moisture field show the cyclonic circulation feature over the Northeast.In rainy years,upper-level jet stream presents the phenomenon of branch at 200 hPa,and the strength of subtropical westerly jet is stronger than normal years.Two ridges and one trough control Asian mid-latitude regions at 500 hPa,and the Northeast is controlled by trough,corresponding to negative geopotential height anomaly.850 hPa wind field has the cyclonic circulation feature over the Northeast,which indicates that a deep low-pressure system controls the Northeast,from low to high levels in troposphere.Circulation features of every layer show that the deep Northeast cold vortex is the leading impact factor of anomalous rainfall over Liaoning Province in early summer in 2012.