2013年四川盆地三次持续性暴雨过程的环流形势和物理成因分析

A Study of Circulation Situation and Environmental Condition of Three Continuous Rainstorm Cases in Sichuan Basin in 2013

利用常规探空和地面自动站观测资料、卫星红外云图TBB和NCEP再分析资料,对2013年6~7月发生在四川盆地的3次持续性暴雨过程进行了大尺度环流背景及物理成因分析。分析结果表明：500h Pa贝加尔湖、鄂霍次克海地区的高压脊起到阻塞作用,利于西伯利亚到巴尔喀什湖附近的深厚低槽稳定分裂短波东南移,槽前持续的正涡度平流向四川盆地输送孕育低层中小尺度系统发生发展,700h Pa西南涡是造成3次暴雨的直接影响系统,其活动对强降水落区有重要作用;850h Pa暖平流维持,在暖平流梯度大值区触发中尺度对流系统产生强降水,暖平流越强降水越强;孟加拉湾的西南暖湿季风气流持续向四川盆地输送水汽和热量,使能量在释放后快速重建,并有适宜的动力环境条件使水汽聚集、辐合和垂直上升,强降水得到持续;700h Pa持续的西南急流在向北加强的过程中南北风分量形成的辐合有利于低层切变线南侧、急流左侧区域的辐合加强,配合高层辐散的抽吸机制,是3次过程强降水持续的又一重要因素。

Using regular sounding data, automatic meteorological observing stations data, satellite images and the reanaly- sis data of NCEP, three continuous rainstorm cases that happened in Sichuan Basin from June to July in 2013 are analyzed re- garding the large - scale circulation backgrounds and physical environment conditions. The results show that the blocking of the high pressure ridge from Lake Baikal and Okhotsk sea at 500hPa help the deep trough near the Siberia and Balk hash Lake splitting shortwave and eastward - moving stably. The positive vorticity advection before the trough transport to the Sichuan Ba- sin continually and bred the genesis and development of the mesoscale and microscale system in the lower layer. The southwest vortex causing three heavy rains is directly influence system, and the activities of southwest vortex have an important effect on the area of strong precipitation. The warm advection at 850hPa maintains. The max region of the warm advection gradients trig- ger mesoscale convective system （MCS） to produce the strong rain, and the stronger the warm advection, the more precipitati- on. The southwest warm - wet monsoon airflow from the Bay of Bengal transport the moisture and heat continuously, which is helpful to rebuilt energy rapidly after release. The proper dynamic environment is beneficial to the vapor gathering, convergence and vertical uplift, which cause the heavy rainfall continued. The convergence caused by the northerly and southerly component of the wind, when the southwest jet at 700hPa strengthening northwards, is beneficial to the convergence become strong near the area of heavy rain, and cooperating with the suction mechanism of high - level divergence, the above mentioned is an important factor of the three heavy rainfall processes maintained.