西北干旱区夏季强干、湿事件降水环流及水汽输送的再分析

Reanalyses of Precipitation Circulation and Vapor Transportation of Severe Dry and Wet Events in Summer in Arid Region of Northwest China

为深入分析西北内陆干旱区夏季降水的主要水汽源地及其输送通道,首先,梳理和评述了过去50年西北干旱区水汽输送的研究进展和问题;接着,利用国家气象局信息中心近50年的实测降水及NCEP/NCAR再分析资料等,挑选更多有代表性的强干、湿日(月)事件,再进行环流和水汽输送的对比分析。主要结论如下:(1)过去西北干旱区各地的干、湿环流研究共识多,进展快;而水汽输送分析依旧众说纷纭。(2)过去的水汽输送分析联系降水环流不够;针对西北干旱区降水特点不够;还应加进数值模拟等分析手段。(3)在本文诊断分析和先前数值模拟基础上,指出西北内陆旱区夏季降水的主要水汽源地在东南沿海一带,它借助西行台风、西伸了的西太平洋副热带高压及柴达木低压等多个天气系统和西太平洋副热带高压西南侧东南风急流、西侧南风低空急流及河西偏东风等三支气流的次第密切配合,首先,水汽被输送到四川盆地;接着,被北输到西北区东部;继而,再被接力西输到河西走廊及南疆盆地东部。谓之"三支气流+两个中转站的三棒接力"式水汽输送模型。它是夏季输向西北内陆旱区的主要水汽输送通道。

In order to further analyze main water vapor origin area and its transportation path for precipitation in summer in inland arid region of Northwest China( NWC),first,the advancements and problems of the water vapor transportation in inland arid region of NWC in past 5 decades were summed up and reviewed,then the many strong,dry and wet month( or day) events in summer in NWC were again selected and the further comparison analyses of their circulation and water vapor transportation were in detail done by using the observed precipitation data etc in past 50 years from National Information Center of China M eteorological Administration and the US NCEP / NCAR reanalysis ones. The main results are shown as follows.( 1) There are many common views and progresses about the dry and wet circulation patterns in the arid regions of NWC summer,but it not trure about their water vapor sources and transportation paths.( 2) The water vapor transportation analyses done in the past decades did not link closely with the dominate precipitation patterns,did not take fully the precipitation features of inland arid area into consideration,and also did not use the test stool of the model simulation.( 3) Based on the diagnostic analyses in the paper and our earlier numerical simulation of water vapor,we point out that the main water vapor origin in the inland arid areas,NWC summer is off the southeast China( SEC) coast,With the aid of both the weather systems: typhoon going westward,West Pacific Subtropical High( WPSH) moving westward and Qidam Basin lows and the flows: southeaster jet on the SW side of WPSH,souther one on the west side of WPSH and the easter in Gansu Corridor,first,the water vapor off the SE coast are transport by the SE jet to Sichuan Basin; then,by the souther jet,to the east part of NWC; again then,by the Easter in Gansu Corridor,to Gansu Corridor and the east part of south Xinjiang. So called as ‘three baton relay water vapor transport model with three flows plus two transfer stations'.