周口市2012年7月4日持续性强对流天气过程分析

Analysis of the Continu-ous Severe Convection Weather in Zhoukou City on July 4,2012

利用NCEP的1°×1°再分系资料和常规天气观测资料,分析2012年7月4—5日河南中东部的持续性强降水天气过程的影响系统,及其演变过程特征和物理量场变化。分析结果表明,①该次持续性强对流天气发生在典型的两槽一脊大尺度环流背景下,稳定维持的副热带高压和冷涡后的冷空气的南下入侵,促使西风槽缓慢东移加深,配合低空激流的频繁活动和西南涡的移出,致使该次强对流天气有一定的持续性,且为强对流的建立和发展提供了条件。②中分析表明,前一时段,"后倾槽"式的整层饱和探空结构对应的短时暴雨天气与实际相同;中间强降水时段,急流在河南中东部的辅合,配合充沛的水汽使热力不稳定加强,更易加强对流的低涡天气,配合急流的位置,使得低涡的移出路线就是强降水的落区;后一时段,急流的缓慢东移使得位于急流左侧的周口东部地区又产生一次降水集中时段后逐渐趋于减弱。③从物理量场分析可看出,较长时间的暖湿水汽供应和垂直上升运动提供了良好的水汽和动力条件。假相当位温剖面图指出,上干冷下暖湿的配置使大气处于层结不稳定状态,给该次降水提供了热力不稳定条件。

NCEP 1°×1°subdivision materials and conventional weather ob- servation data were used to analyze the influence system of continuous severe convection weather in central and eastern Henan during July 4 and 5, 2012, as well as its evolution features and changes of physical quantity field. The results showed that （a） this continuous severe convection weather occurred against the background of typical ＂two troughs and one ridge＂ large-scale circulation, the stably-maintained subtropical high pres- sure and cold air after cold vortex moved southwards to push westerly trough east- wards slowly. In addition, frequent low-altitude torrent and shifting south- west vortex contributed to the continuity of this severe convection weather, and laid a solid condition for the establish- ment and development of severe convec- tion weather. （b） According to the meso- analysis, in the previous stage, the short-term rainstorm corresponding to ＂tilting trough＂ saturated sounding struc- tures of the whole layer complied with the actual conditions; during the mid- die-period strong rainfall, torrents met in eastern and central Henan, the abundant moisture enhanced the instability of heat, especially low vortex of convection. The shifting-out route of the low vortex was the precipitation area. In the later period, torrents moved eastwards slowly, so east- ern Zhoukou in the left side of torrents witnessed another concentrated rainfall and then torrents declined gradually. （c） From the perspective of physical quantity field, long-term warm-humid moisture supply and vertical ascent guaranteed fa- vorable moisture and dynamic condi- tions. According to profile map of equiv- alent potential temperature, the dry and cold air in the upper layer and warm and humid air in the lower layer led in insta- ble atmospheric stratification, and pro- vided thermal instability for the rainfall.