1999年梅雨锋系结构特征的模拟诊断  

A diagnostic analysis of the simulated structure of the meiyu front system in 1999.

作　　者：崔晓鹏[1] 高守亭[1] 张海霞[2] 郝世峰 

机构地区：[1]中国科学院大气物理研究所云降水物理与强风暴实验室,北京100029 [2]河北省邯郸市气象局,邯郸056001 [3]浙江省气象科学研究所,杭州310017

出　　处：《气象学报》2008年第1期26-34,共9页Acta Meteorologica Sinica

基　　金：国家自然科学基金项目(40505012,40433007);中国科学院知识创新工程领域前沿项目(IAP07214)

摘　　要：通过中尺度模式MM5对1999年江淮流域一次梅雨锋暴雨过程的数值模拟,利用高分辨率模拟资料,诊断了江淮地区梅雨锋系的双锋结构特征及相应的大气相当位温、位温和湿度(比湿)分布特征。结果表明,大气位温梯度和湿度梯度均对江淮梅雨锋系双锋结构中相应的两个相当位温梯度大值带的存在有着重要贡献,而湿度梯度的贡献更大。进而从理论上推导了大气湿度梯度倾向方程,指出大气湿度梯度的变化与平流效应、散度效应、水平或垂直涡管(次级环流)效应以及水汽源汇的梯度有关;利用中尺度模拟资料对湿度梯度倾向方程的经向分量进行了简单的方程诊断,模拟时段平均的诊断分析表明,大气经向湿度梯度绝对值的变化主要同散度效应、与水平涡管相关的次级环流效应以及水汽源汇效应相关。由于水汽源汇是由与水汽相关的相变过程造成,与云物理过程的发展和演变直接相关,因此,大气湿度梯度的演变与云物理过程,并进而与云或降水系统的分布、发展和演变相关。梅雨锋系的存在为其附近暴雨中尺度系统的发展提供了有利的环境条件,起到一定的组织或控制作用;反过来,暴雨系统的发展、降水云系的发展和演变,又通过改变大气温、湿状况,对梅雨锋系产生影响。A numerical simulation of a torrential rain event occurring in the Jiang-Huai valley of China from June 22 to 24, 1999 by using the PSU/NCAR MM5 mesoscale non-hydrostatic model is analyzed, and the high-resolution model output data are utilized to diagnose the double front structure, and the relevant potential temperature, equivalent potential temperature and specific humidity distributions in the vicinity of the meiyu front system （MYFS） in the Jiang-Huai valley. The results show that both the potential temperature gradient and specific humidity gradient have important impact on the two strong equivalent potential temperature gradient zones associated with the double front structures of the MYFS, but the latter is more important to the structure. Then the tendency equation of specific humidity gradient is theoretically derived, and it shows that the variation of specific humidity gradient is related to the advection, divergence/convergence, horizontal and vertical vortex tube （secondary circulation） effects and the gradient of water vapor source/sink. As an example, the budget of the meridional component of the trend equation is selected and diagnosed by using the above mentioned mesoscale simulation data of the torrential rain in the Jiang-Huai valley, and the diagnostic results show that the temporal variation of the averaged specific humidity gradient over the duration of the simulation is mainly related with convergence/divergence effect, secondary circulation effect associated with horizontal vortex tube, and water vapor source/sink effect. Since the water vapor source/sink is often resulted from the phase change processes associated with the water vapor in air and thus directly related with the development and evolution of cloud and precipitation microphysical processes. Therefore, the variation of specific humidity gradient is close related to the distribution, development and evolution of cloud and precipitation systems. The double front structure of the MYFS provides advantageous environmental c

关 键 词：梅雨锋系 双锋结构 湿度梯度 倾向方程 

分 类 号：P441[天文地球—大气科学及气象学]