安徽汛期淮北区域性暴雨大尺度环流特征及成因分析

Anhui Huaibei Regional Rainstorm Circulation Features and Causes of Large Scale Analysis

本研究利用合成分析、EOF分解、显著性差异检验、相关分析等方法对1960—2010年安徽淮北地区5—9月25个区域性暴雨个例进行分析来研究安徽地区淮河以北区域性暴雨时空分布、大尺度环流分型及物理量场分布特征,从气候背景角度出发了解其成因分析,为预报提供有益参考。研究表明:安徽淮北区域性暴雨大尺度环流特征主要表现为两脊两槽型。暴雨区多位于高空西风急流入口区南侧和低层低涡辐合中心东南侧、闭合经向垂直环流上升支下方。冷空气分别从高低层同时入侵,高层冷空气以高值位涡柱的形式向下入侵。暴雨区多位于垂直上升速度中心和湿位涡负值中心略偏北,垂直方向上呈现湿位涡正负区叠置的形势,且低层的对流不稳定和中高层的斜压不稳定相结合,使得大气不稳定性增强是造成淮北区域性暴雨的主要原因。

Analysis of 25 regional rainstorm in Anhui Huaibei area from May to September during 1960- 2010 showed that： Huaibei regional rainstorm flood time evolution had＇ early July to late August＇ feature. The EOF analysis found that features the regional rainstorm in Huaibei large scale circulation were two ridges and two grooves. The rainstorm area is located in the south side of the entrance of the upper westerly jet and low-level vortex convergence center southeast side, closed the meridional vertical circulation ascending branch. The cold air from high layer and the upper cold air intrusion, with high value of potential vorticity column form downward intrusion. The rainstorm area is located in the center of the vertical velocity and moist potential vorticity negative center north, vertical direction is moist potential vorticity positive and negative overlapping situation, and the low layer baroclinie convective instability and the high-level unstably combined, enhanced the atmospheric instability is proved to be a major cause of regional rainstorm in Huaibei.