2005年河南省秋季持续阴雨天气成因分析

Cause Analysis of an Continuous Rain Weather in Autumn 2005 in Henan

利用NCEP/NCAR 2.5°×2.5°日平均再分析资料和1°×1°资料及常规气象观测资料,分析了河南省2005年9月14日-10月3日长达18天(18日、22日间歇)的连阴雨天气成因。结果表明:200 hPa出现并且维持的高空急流,异常强大的南亚高压,偏西偏北的副热带高压,以及边界层的偏东风,是造成此次连阴雨天气的主要影响系统;高层辐散、低层辐合是阴雨天气持续的动力机制;充足的水汽供给,配合强的水汽辐合以及底层偏东风长时间的维持,是这次连阴雨天气降水量较大的主要原因。强冷空气南下、边界层东北急流出现、副高明显东退,使得持续十几天的连阴雨天气彻底结束。

Based on the NCEP/NCAR 2.5°×2.5° daily average reanalysis data,1°×1° data and the conventional meteorological observation data,a diagnostic analysis was conducted for 18-days long continuous rain from 14th September to 3rd October except 18th and 22nd September.The result shows the main influence system including the appearance and maintenance of 200 hPa upper-level jet,the exceptional strong South Asian high,subtropical anticyclone lying in the north by west than normal and the northeast wind in boundary layer.The divergence at upper and the convergence at low level were the dynamic mechanism causing the continuous rain weather.The ample vapor supply cooperated with the strong vapor convergence and long-time maintenance of the rock-bottom easterlies were the main reasons that caused a biggish precipitation in the continuous rain weather.The 18-days long continuous rain weather was terminated by the strong cold air going down to the south,the appearance of northeaster jet stream in boundary layer and the subtropical anticyclone retracting to the east.