利用JTWC、NCEP/NCAR再分析资料、TRMM变分同化资料，对2000-2010年初夏孟加拉湾风暴过程中，有、无冷空气配合时对云南强降水的不同作用进行了合成对比分析。结果表明，初夏影响云南强降水的孟加拉湾风暴，均在孟加拉国东南部、缅甸中北部沿海一带登陆，其中约78%强降水都是在风暴登陆以后产生的。除东部边缘外，云南大部分地区都易受孟加拉湾风暴影响，当有冷空气作用时，云南大到暴雨的范围更广、强度更强，环流的演变与风暴强降水区密切相关。进一步对比分析表明，当无冷空气配合时，强降水当天南风明显增强，且最大风速中心随高度向北倾斜，垂直风切变小，湿层深厚，风暴暖湿气流带来的对流不稳定是滇西产生强降水的重要原因，此外地形强迫抬升也起着重要作用。当有冷空气配合时，强降水开始时刻，沿着云南地形有一向北倾斜的θ_se密集带，倾斜等熵面南侧有暖湿风暴云团向北倾斜上滑，而北端对流层中低层为干冷气流，它们在倾斜的等熵面上交汇，偏向暖湿气流区存在向北倾斜的上升运动区，强降水过程中，北端锲入气流更为干冷，与开始时刻相比，上升运动更为陡立；湿位涡方面，滇南北侧高层有高值湿正压项MPV1沿着倾斜的等熵面向降水区下传，下滑冷空气的强迫加强了南侧暖湿气流的上滑，同时，强降水以北的高层有MPV2负值中心沿θ_se等值线密集带从对流层高层倾斜侵入对流层低层，冷暖空气在对流层中低层相遇，产生条件性对称不稳定，导致滇中以南地区出现强降水。

Based on JTWC, NCEP/NCAR reanalysis data and variational assimilation of TRMM, the activity of cold air and its impacts on Bengal Bay storm heavy rainfall in Yunnan in early summer from 2000 to 2010 were diagnosed. It was showed that Bengal Bay storm initiating heavy rainfall over Yunnan in early summer both landed at the southeast of Bangladesh, north centre coast of Burma, among them about 78 percents of heavy rainfall appeared after Bengal Bay storm landing. Except for eastern edge, the subtotal areas of Yunnan were easy to be affected by Bengal Bay storm. While there was cold air acting, the intensity of heavy-hard rain was stronger and range was wider. The evolution of circulation was closely related to storm heavy rainfall areas. Further discussion showed without cold air, southerly enhanced significantly, and the wind speed maximum sloped northward with height, vertical wind shear was small, moist layer was deep, convective instability occurred by storm warm-wet air was the important reason for heavy rainfall over western Yunnan, moreover topographic forcing also played an important role. Otherwise, while cold air acting, there was an intensive belt of θ_se sloping northward at the beginning of heavy rainfall, warm-wet storm clusters tilt upward-slided along southern isentropic surface, whereas there was dry-cold air in the middle-low troposphere at the side of north, they met at tilt isentropic surface, ascending motion areas sloping northward was bias to warm-wet region, during heavy rainfall periods, cold air changed more dry-cold, compared with the beginning, ascending motion was more stiff. In the aspect of moist potential vorticity, there was high MPV1 downloading to precipitation area along tilt isentropic surface at upper layer of the north side of southern Yunnan, the forcing of down-sliding cold air strengthened the upward-sliding of warm-wet air, meantime, negative center of MPV2 downloaded along intensive belt of θ_se from high troposphere and invaded low troposphere at the north side of heavy rainfall areas, warm-wet air met with dry-cold air at middle-low troposphere, then conditional symmetric instability generated, which resulted in heavy rainfall over central Yunnan and the south areas.