不同环境风场条件下两次暴雨过程对比分析

Comparative Analysis of Two Heavy Rainfall Processes under Different Environmental Wind Field Conditions

利用NCE再分析资料从动力条件,水汽条件和不稳定能量三个方面对比分析了分别处于强和弱环境风场条件下,均为受高空华北槽、低空切变线影响的两次广西暴雨过程,结果表明:(1)两次暴雨过程发生发展均表现出低层辐合、高层辐散,伴随上升运动的特征,低层有水汽辐合,且大气处于不稳定状态,说明在华南西部无论关有无急流建立,只要满足一定的条件,强降水就可发生。(2)强环境风场条件下的暴雨过程大气较湿,水汽较充沛,动力条件较好,弱环境风场条件下的暴雨过程低层水汽辐合较强,两次过程的降水强度相当,可能表明了强环境风场的作用在于提高了动力条件和水汽含量,而华南暴雨过程的形成,水汽辐合条件影响权重更大。

Based on NECP/NCAR reanalysis data, two heavy rainfall events with different environmental wind field condition, which were triggered by upper-level North China Trough and low-level shear were comparative analyzed. The results show that 1 ） Two storm events both had the same characteristics of unstable atmosphere state of low-level convergence and high-level divergence. It indicates the heavy rain can occur without Low - level Jet as long as certain conditions are met.2） the rainstorm process is under strong （weak） environmental wind field with abundant vapor and suitable dynamic conditions （strong Low-level moisture convergence）. The considerable rainfall intensity of this two rain processes indicate that the formation of the South China rainstorm process mainly depends on the moisture convergence conditions.