南亚高压和高低空急流对2010年浙江梅汛期暴雨的影响

利用常规气象站资料和美国NCEP/NCAR再分析资料,分析了2010年浙江梅汛期降水特征及南亚高压和高低空急流对梅汛期暴雨的影响。结果表明:(1)2010年浙江入、出梅偏晚,梅期明显偏长;降水偏多,强降水集中在浙江西南部,并逐渐向南北阶梯递减;暴雨过程频繁,降水集中,阶段性明显;(2)梅汛期间南亚高压主体偏强,加强中南北振荡和东西进退明显。高压脊线的南北振荡与强雨带南北摆动有一定的相关性。南亚高压在稳定状态或变化时都可能产生暴雨,暴雨多发生于变化时,且高压的西退与南撤同步,东进与北抬同步;(3)梅汛期高低空急流的演变具有较好的一致性,且与暴雨时空对应较好。暴雨带多处于高空急流的右侧和低空急流轴的左侧,暴雨带随高低空急流的位置变化而南北摆动,同时,低空急流轴到急流北缘与暴雨带有不同程度重叠。高低空急流强度与降雨强度有较密切的关系,高低空急流的水平距离对高低空急流耦合作用有重要影响,进而影响垂直运动发展和降水强度。因此,高低空急流的配置对梅汛期暴雨落区和强度预报有很好的指示意义。

The effect of south Asia high and upper and lower-level jets on Meiyu rainstorm in Zhejiang province during 2010

Using the conventional data and NCEP/NCAR reanalysis data,this paper analyses the rainfall characters in Meiyu period of Zhejiang province during 2010 and the effects of South Asia high and upper and lower-level jets on Meiyu rainstorm.The results show that(1) The beginning and the ending of Meiyu in Zhejiang province during 2010 were later,and the Meiyu period was obviously longer; the precipitation was more,and heavy precipitation concentrated on southwest of Zhejiang province,moreover it showed gradual decrease step by step towards south and north; rainstorm processes were frequent and concentrated. (2) In Meiyu period,the body of South Asia high was stronger,south-north oscillation and east-west sway were obvious in the process of the gradual strengthening,and south-north oscillation synchronized with westward and eastward shift. There was corresponding between south-north oscillation of South Asia high ridge line and south-north shift of rainstorm. Rainstorm was possible whether South Asia high was stable or changed. Rainstorm mostly occurred when South Asia high changed,and southward movement was synchronous with westward,northward was synchronous with eastward.(3) In Meiyu period,the evolution of upper and lower-level jets was consistent,and there was space-time corresponding between upper and lower-level jets and rainstorm.Rainstorm belt was mostly located in the right side of upper-level jet and the left side of lower-level jet axis,and it swayed south-north with the location of upper and lower-level jets.Moreover,to a certain degrees, the movement of lower-level jet from axis to north edge was coincident with rainstorm belt.The intensity of upper and lower-level jets was closely related to rainfall.The horizontal distance had important influence on the coupling between upper and lower-level jets,and then it effected the development of vertical velocity and precipitation intensity.Therefore,the configuration of upper and lower-level jets has good indication to area and intensity of rainstorm in Meiyu period.