“8.25”曲靖突发局地大暴雨的中尺度系统特征分析和数值模拟

“8.25”曲靖突发性局地大暴雨,在近30年来8月强降雨中是罕见的。采用Barnes带通滤波方法分离出中尺度天气系统表明,500hPa上的中尺度低压扰动系统和700hPa上的中尺度低涡是产生这次暴雨天气过程的直接的天气系统。在潜在不稳定条件下,由于中尺度系统的扰动,局地水汽强烈辐合,造成了此次强降水。同时中尺度数值模式MM5结果很好地模拟了这次局地暴雨过程的落区、雨强以及发生和发展。强降水发生时有强的上升运动与深厚饱和气柱互耦结构是富源、马龙大暴雨产生的重要动力机制。师宗站上升运动主要出现在对流层中高层,降雨量与上述两站相比要小得多。深对流气柱内云团发展的微物理结构显示,造成富源大暴雨的强对流云不是只含有云水和雨水的暖云云体,在对流层高层有含有雪和冰的混合相云体。马龙暴雨的强对流云团的微物理结构上在对流层中低层与富源云团性质一样,同属暖云云体,但云水合比和雨水混合比均比富源云团小,在对流层高层马龙云团为仅含有雪的单一云体。师宗云团与上述两站均不同,雨水混合比在3者之中最小,产生强降水的主要是对流层高层含有雪和冰的混合相云体。

AN ANALYSIS OF MESOSCALE SYSTEM AND NUMERICAL SIMULATION ON THE OCURRENCE CAUSE OF A LOCALLY SUDDEN TORRENTIAL RAIN IN QUJING AREA ON 25 AUGUST

The locally sudden torrential rain in Qujing area on 25 August has been seldom in recent 30 years.The analysis of mesoscale system shows that disturbi ng mesoscale low pressure system at 500 hPa and mesoscale vortex at 700 hPa are directly influential systems which caused the heavy rain process.Meantime,the M M5 mesoscale numerical model successfully stimulated the droppoint,intensity,g eneration and development of the locally sudden torrential rain.The most importa nt motivated mechanism which caused the heavy rain in Fuyuan and Malong is the c oupling of stronger ascending motion and profound saturation air column.In Shizh ong,the ascending motion mainly occurred in middle and high troposphere and it 's precipitation is smallest among three stations.The micro physical structure of deep convection of developing air column shows that the heavy convective clo ud in Fuyuan includes not only warm cloud which is composed of cloud water and r ain water,but also mixted phase cloud which is composed of snow and ice in high troposphere. The micro physical structure of Shizhong's cloud in low and middl e troposphere is similar to Fuyuan's,but the mixing ratio of cloud water and ra in water is smaller than Fuyuan's and in high troposphere Malong cloud is only composed of snow.However,Shizhong cloud is different from Fuyuan and Malong clo ud,it's mixing ratio of rain and water is the least.It is the mixed phase cloud in high troposphere which brings the heavy rain.