华南暖区暴雨的一种低层重力波触发机制  

A Low-Level Gravity Wave Triggering Mechanism For Rainstorm of Warm Zone in South China

作　　者：徐燚 闫敬华[2] 王谦谦[3] 董加斌[1] 

机构地区：[1]浙江省气象台,浙江杭州310021 [2]中国气象局广州热带海洋研究所,广东广州510080 [3]南京信息工程大学,江苏南京210044

出　　处：《高原气象》2013年第4期1050-1061,共12页Plateau Meteorology

基　　金：科技部基础条件平台项目(2003DIB4J145);浙江省气象局一般项目(2011YB01)

摘　　要：利用观测资料和高时空分辨率区域数值模式,对华南一次锋前暖区暴雨进行了分析和数值模拟。结果表明,锋区和暖区逐时降水呈波列状分布,锋区和暖区850hPa散度在各区降水开始之前1～2h出现剧烈振动,暖区振动比锋区约晚1h;降水时锋区和暖区间各点850hPa逐时散度增量也呈明显的波状分布。小波分析证实锋区和暖区存在周期相同且差半个位相的波动,波动的特性属于重力波。进一步分析发现,在暖区暴雨发生之前3h左右,锋区到暖区之间存在一非常浅薄的低层稳定层,位于950～850hPa之间。这一浅薄稳定层的存在满足重力波传播的条件,使锋区对流激发的低层重力波沿稳定层从锋区向暖区传播,激发了暖区低层的上升运动,并触发暖区中、低层不稳定能量的释放,导致暖区暴雨的发生。A warm zone rainstorm before front in South China was analysed and high-resolution numerical simulation was done using the high resolution observational data and regional model.The results show that the distribution of hourly rainfall at frontal and warm zones is a wave train,and 850 hPa divergence at frontal and warm zones appear acute oscillation at 1~2 h before the rain beginning,and the oscillation is later about 1 h at warm sector than that of frontal zone.Hourly divergence increments on 850 hPa for grids along the line linking frontal and warm zones distribute distinctly as a wave train too.Wavelet analysis approve that there are two waves with same period and different half phase at frontal and warm zones,and the waves belong to gravity wave.Further analysis indicate that about 3 h before warm zone rainstorm beginning,there is a very superficial low-level stable layer locate at 950~850 hPa approximately between frontal and warm zones,and the stable layer＇s presence satisfy the propagating situation of gravity wave,and when a low-level gravity wave is excitated by front convection,it would propagated from frontal to warm zones along the stable layer,then excitated low-level ascending motion at warm zone.Updraft touches off the release of middle and low level unstable energy and then generated a warm zone rainstorm.

关 键 词：华南暖区暴雨 低层浅薄稳定层 低层重力波 数值模拟 

分 类 号：P435.1[天文地球—大气科学及气象学]