摘要
采用合成平均分析方法，对2011年7月中旬江淮流域持续降水过程和11～13日大暴雨的大尺度环流和物理量进行了诊断，分析表明：（1）持续降水过程大尺度环流是不典型的双阻型，西脊在乌拉尔山以西地区，东脊在雅库茨克。副热带高压位置偏东脊线偏北。贝加尔湖东南方的低槽从蒙古经河套伸向华南，江淮流域处于槽前稳定的西南气流中。巴尔喀什湖低槽的加深东移及其底部不断分裂的短波槽，造成了持续降水期间的大暴雨过程。（2）江淮流域位于高空西南急流入口区右侧，低空风速大值带左侧。水汽主要来自孟加拉湾、南海和西太平洋地区，高低空的强烈辐散辐合所造成的深厚上升运动为暴雨提供了动力条件，对称不稳定为暴雨提供了不稳定机制。
Using upper and ground based observations data, by means of Cressman＇ s objective analysis and com- posite analysis method, the large scale features of persistent rainfall which occurred from 10 to 20 July, 2011 over the whole Yangtze-Huaihe region （26-34ο^N, 110-122ο^N, including the Yangtze River and the Huaihe River val- leys） are studied, and the rainstorm occurred in this period from 11 to 13 is dynamically diagnosed. The results are as follows ： （ 1 ） There are double ridge of high pressure and one trough around 50-70ο^N in the large scale circulation field, the western one is over the Ural Mountains （at 40ο^E）, the eastern one is over Yakusk （at 130ο^E）, and it is the trough over the Lake Balkhash between them, as well as nontypical double-blocking high type. As the trough is mov- ing eastwardly and deepening, the short-waves trough which split from the bottom of it brings about the heavy rain. The Western Pacific Subtropical Anticyclone is by eastern and its ridge is by northern. A deep trough over the south- east of Lake Baikal extends to the Southern China from Mongolia, the southwestward airflow of the ahead of the trough impacts the Jianghuai Basin steadily. （2） The Yangtze-Huaihe region is located on the right side of the high level southwest jet＇ s entrance area and the nearside of the low level south jet. The dry cold air comes from the mid- high latitudes and the mid-high level, the dry cold air intrusion contributes to the formation and maintenance of the dry level. The dry cold air intrusion is one of the important dynamical and thermal causes for the formation and maintenance of moist front during the Meiyu period. （3） The water humidity comes largely from two sources, one is at the Bay of Bengal whose humidity is transferred by westerly flow on the south side of the monsoon depression via the Indo-China peninsula into the Sea and advancing northward into the Yangtze-Huaihe region, and the other is over the South-China Sea which offers water vapor for the rainband mainly through SW monsoon. （4） The cyclonic vorticity and convergence at the low level, the anticyclonic vorticity and divergence at the upper level, deep upward motion plays a main role in the maintenance of sever precipitation occurred in 11-13 July, 2011. Based on the moist potential vorticity （MPV） theory, the vertical and horizontal components of MPV, MPV1 and MPV2 are analyzed; symmetric instability is related with convective instability, inertial instability, moist baroclinicity and vertical wind shear. It is favourable to develop symmetric instability when MPV1 〈0, MPV2 〈 0, the symmetric instability intensi- fied the torrential rain. The conditional symmetric instability （MPV〈O） provided favorable instability mechanism for the occurrence of rainstorm.
出处
《干旱区地理》
CSCD
北大核心
2014年第4期684-695,共12页
Arid Land Geography
基金
公益性行业(气象)科研专项<多时间尺度干旱监测预警
评估技术研究>(GYHY201006023)资助
关键词
江淮流域
持续降水
大尺度
环流特征
Yangtze-Huaihe region
persistence rainfall
large scale
circ,,lation character
