利用逐时卫星云图、 雷达回波、 自动雨量站等加密观测资料和NCEP/NCAR 1°×1° 再分析资料, 分析了云南4次特大暴雨的成因。结果表明, 这4次突发性特大暴雨过程主要是中低层低涡切变线、 西南气流的辐合造成水汽、 能量的聚积， 低层增暖增湿， 500 hPa干冷空气入侵， 形成强对流不稳定区； 当低层水汽充足、 局地大气具有潜在不稳定能量和适当的触发条件时， 在500 hPa槽后易产生特大暴雨天气\.卫星云图显示， 特大暴雨过程由对流单体合并、 加强为中尺度对流云团引起的。在雷达回波发展、 移动过程中， 始终存在回波合并效应， 前部回波移动缓慢， 后部中小尺度回波活动频繁， 小单体快速生成合并， 使得整块回波稳定少动， 在强降雨阶段存在较强的风向、 风速辐合。

The satellite cloud image, radar, automatic rainfall station observing cryptographic data and NCEP/NCAR 1°×1° reanalysis data are used to analyze the forming reason of four extraordinary heavy rainstorm events happened in Yunnan Province. The result indicated that, the sudden rainstorm process main is the convergence of low vortex shear line on mid-lower layers  and  southwest airflow to cause the accumulation of vapor, energy, warming and humidifying on lower layer, and 500 hPa dry and cold air intrusion on the layer that form convective instability area, which made sudden torrential rainstrom. When the vapor is rich on lower layer and the local atmosphere is potentially unstable or has proper toggle conditions, heavy torrential rainstrom event happen easily in the area under the control of northwest current.  The satellite cloud image revealed that the convective clouds' merging and strengthening to mesoscale convective cloud lead to the torrential rainstrom event.  In the moving  and development processes of radar echo, the merging effect always happened with the moving of echoes. The echo forward move slowly but the its backward develope frequently, so little monomers generate and merge fast, which make the whole block echo steady. And the stronger convergence of wind direction and wind speed appeared at the stage of severe precipitation.