夏初850hPa西太副高异常对江淮流域降水影响

Influence of the 850 hPa WPSH Abnormality on Rainfall in Jiang-Huai Basin in Early Summer

[目的]研究夏初850 hPa西太平洋副高的异常对江淮流域降水的影响。[方法]利用NCEP/NCAR 2.5°×2.5°的分析资料,采用合成分析、相关分析等方法,对位势高度场、纬向风场、降水率、垂直速度场等与副高指数相关联的环流和降水异常进行了分析,探讨夏初850 hPa西太平洋副高的异常对江淮流域降水的影响。[结果]夏初西太平洋850 hPa副热带高压的异常对江淮流域降水有重要影响。夏初西太平洋副高面积偏小、脊点偏东、偏北时,500 hPa高度场上鄂霍次克海地区无阻塞型控制,高纬冷空气路径偏北,梅雨锋区低压扰动减弱,东亚夏季风环流加强,江淮流域冷空气偏弱,使得江淮流域降水偏少;夏初西太平洋副高面积偏大、脊点偏西、偏南时,500 hPa高度场上鄂霍次克海地区为阻塞高压控制,梅雨锋区低压扰动加强,东亚夏季风环流减弱,江淮流域冷空气偏强,使得江淮流域降水偏多。[结论]该研究为江淮流域的降水异常提供指示作用。

[Objective] The research aimed to study influence of the 850 hPa WPSH abnormality on rainfall in Jiang-huai basin in early summer.[Method] Based on NCEP/NCAR 2.5°×2.5° analysis data,by using composite analysis,correlation analysis and so on,circulation and rainfall abnormalities were analyzed.Subtropical index related to geopotential height field,zonal wind field,precipitation rate,vertical velocity field and so on.Influence of the 850 hPa WPSH abnormality on rainfall in Jiang-huai basin in early summer was discussed.[Result] 850 hPa WPSH abnormality had important influence on rainfall in Jiang-huai basin in early summer.When WPSH area was small in early summer,and ridge point was by east and north,there was no blocking control in Okhotsk area at 500 hPa height field,and pathway of the cold air at high latitude was by north.Low-pressure disturbance in plum rain frontal zone weakened,and East Asian summer monsoon circulation strengthened.Cold air in Jiang-huai basin was weak,which caused less precipitation in Jiang-huai basin.When WPSH area was big in early summer,and ridge point was by west and south,it was blocking high control in Okhotsk area at 500 hPa height field.Low-pressure disturbance in plum rain frontal zone strengthened,and East Asian summer monsoon circulation weakened.Cold air in Jiang-huai basin was strong,which caused more precipitation in Jiang-huai basin.[Conclusion] The research played indicative role in precipitation abnormality in Jiang-huai basin.