一次梅雨锋暴雨过程中的重力波特征

Characteristics of Gravity Wave of a Meiyu Front Heavy Rainfall from 7 to 9 July 2007

利用中尺度数值模式WRF模拟了2007年7月7～9日江淮地区发生的一次梅雨锋暴雨过程,通过动力分析和Morlet小波分析方法研究了此次梅雨锋的重力波特征。结果表明：2种非平衡流诊断指标（Ro和ΔNBE）简易有效,梅雨锋暴雨过程中的中尺度重力波系统垂直结构十分清晰;强波动发生时段集中在7日20时至8日06时,30～80 min短周期重力波能量远高于长周期;重力波在低层表现强烈,中高层的短周期能密度中心出现更早;最强波动时段与强对流相对应,波动与对流形成耦合,动力与统计分析相互补充,效果较好。

Based on the hourly precipitation and NCEP reanalysis with 1° × 1° spatial resolution,a Meiyu front heavy rainfall process from 7 to 9 July 2007 was simulated by WRF model. On this basis the characteristics of meso- scale gravity wave（ MGW） were analyzed by using the dynamic analysis and Morlet wavelet method. The results showed that two indicators including Ro and Δ NBE were easy and effective to diagnose unbalanced flow. The vertical structure of mesoscale gravity wave was clear during the rainstorm. The strong fluctuation of gravity wave was concentrated from 20： 00 UTC 7 July to 06： 00 UTC 8 July,and the gravity waves were dominated by the short- period with 30- 80 min. Meanwhile the fluctuation in the middle and low layers was stronger than that in the upper layers,and the short- period gravity waves was stronger than that of the long- period ones at all vertical layers. The severe convection was related with the strong fluctuation of short- period gravity waves and both of them were coupled together,which was consistent with the CISK theory. Morlet wavelet analysis of atmospheric gravity waves can effectively make up for the disadvantages of dynamic analysis,and their coupled effect was better to provide meteorological service for flying and air safety.