Abstract:

Diagnostic analysis and numeric simulation were made on a heavy rain process in the southeast part of Gansu during 1 － 2 July
2005 using NCEP data of 1° × 1° with 6 h intervals and WRFV3． 1 meso － scale model． Based on the data of model output，the relation
between the helicity of this process and the rainfall intensity was analyzed． The results show that the short － wave trough from Plateau
and the moisture from South China Sea and Bengal were important causes of the heavy rain process． WRF model had the ability of
simulating this heavy rain’s precipitation; The spatial distribution of the helicity had certain indication about prediction of heavy rain in
eastern part of northwest China． The shape of maximum value center of positive helicity correlated with the shapes of short － wave trough
from Plateau and shear line on 700 hPa; The maximum value center of positive helicity which occurred under 400 hPa may be a great
cause for heavy rain in northwest part of China．

Key words: heavy rain, diagnostic analysis, numeric simulation, helicity

摘要：

: 利用NCEP 每6 h 一次的1° × 1°格点资料和中尺度模式WRF( V3． 1) ，对2005 年7 月1 ～ 2 日发生在甘肃东南部的一次暴雨天气进行了诊断分析和数值模拟，运用模式输出资料对本次天气过程的螺旋度与降水的关系进行了分析讨论。结果表明: 高原短波槽的生成，以及来自南海和孟加拉湾的水汽输送是造成此次暴雨天气过程的主要原因; WRF 模式对西北暴雨具有一定的模拟能力; 螺旋度的空间分布对西北地区东部暴雨的预报具有一定的指示意义; 700 hPa 正值螺旋度的分布形状与高原短波槽和700 hPa 切变线的形状存在对应关系; 而400 hPa 以下大值正螺旋度的产生可能是西北暴雨发生发展的重要原因之一。

关键词: 暴雨, 诊断分析, 数值模拟, 螺旋度