影响重庆夏季暴雨的中尺度低涡的气候学特征

The Summery Heavy Rainfall Climatic Characteristics Associated with the Mesocale Low Vortex over Chongqing

为揭示对流层中低层中尺度低涡影响重庆夏季暴雨的可能原因,使用1979~2011年1°×1°的ECMWF再分析资料和重庆市逐日降水资料,采用天气学诊断、合成分析等方法,在对重庆低涡暴雨定义的基础上,从天气、气候学角度,对重庆低涡导致的重庆暴雨进行分析。结果表明,30余年来,重庆低涡导致的重庆暴雨共有26例,重庆低涡导致的暴雨降水量和暴雨次数在空间分布上并不相同,重庆低涡导致的暴雨降水量最大值主要位于重庆中南部,而重庆低涡暴雨次数最大值区域则主要位于重庆的西南。导致重庆夏季暴雨的重庆低涡在700 h Pa上空主要为一个闭合的低压,重庆暴雨发生次数最多的地区主要位于从重庆垫江到南川槽线的西北部;700 h Pa上重庆西部的θse的＂槽＂和＂脊＂,使冷暖空气在重庆地区交汇,非常有利于重庆暴雨的发生。在对流层中层,和重庆低涡相对应的是一高空槽;重庆暴雨主要位于高空急流出口区的右侧。重庆低涡垂直结构表明,其在对流层低层主要表现为气旋性辐合环流,在对流层中高层则为反气旋性辐散环流,这样的垂直空间配置,使重庆上空从对流层低层到对流层顶层附近,都为明显的上升运动;强烈的上升运动和来自孟加拉湾、南海以及重庆西北部的水汽,使得重庆西边界、北边界以及南边界呈现为水汽输入边界,水汽在重庆地区辐合盈余,导致重庆夏季暴雨的发生。

In order to reveal the possible reason that the mesoscale low vortex in the lower troposphere affect the summer heavy rainfall in the Chongqing area,ECMWF reanalysis data and Chongqing daily precipitation data us the weather diagnosis and analysis synthesis methods ased on the definition of the Chongqing vortex heavy rainfall,then from the weather and climate perspective,the heavy rainfall caused by the Chongqing Vortex. The results show that,more than30 years,the Chongqing Vortex have cased Chongqing heavy rainfall in a total of 26 cases. The precipitation and frequency of heavy rainfall caused by Chongqing vortex are not the same in the space distribution. The maximum of heavy rainfall precipitation is mainly located in the central and southern Chongqing,but the frequency maximum area is mainly located in the southwest Chongqing. On 700 h Pa the Chongqing vortex which caused Chongqing summer heavy rainfall is a closed low pressure. The region that Chongqing heavy rainfall occurrs most frequently is mainly located in the north-west of trough-line from Chongqing Dianjiang to Nanchuan. On 700 h Pa the θse ＂ trough＂ in west Chongqing and its ＂ridge＂ over Chongqing make the intersection of cold and warm air in the Chongqing region,which is very conducive to Chongqing heavy rainfall occur. In the middle troposphere,corresponding to the Chongqing vortex is an upper trough.Chongqing heavy rainfall is mainly located in the right side of upper-level jet stream outlet zone. The Chongqing vortex vertical structure show that it is convergence cyclonic circulation in the lower troposphere and is divergent anticyclonic circulation in the upper troposphere,an obvious upward movement from the lower troposphere to top over Chongqing.The strong upward movement and the water moisture from the Bay of Bengal,South China Sea and the northwestern Chongqing moisture make the Chongqing west boundary,northern boundary and southern boundary appear as input border of water vapor,which lead to the moisture convergence and surplus and final result the summer heavy rainfall occur in Chongqing.