强降水云物理过程的三维数值模拟研究  

A Three-Dimensional Numerical Simulation on Microphysical Processes of Torrential Rainstorms

作　　者：肖辉[1] 王孝波[1] 周非非[1] 洪延超[1] 黄美元[1] 

机构地区：[1]中国科学院大气物理研究所,北京100029

出　　处：《大气科学》2004年第3期385-404,共20页Chinese Journal of Atmospheric Sciences

基　　金：国家重点基础研究规划项目G1 9980 40 90 7 0 2 0 3;国家"十五"科技攻关计划2 0 0 1BA61 0A 0 6 0 5专题;国家自然科学基金资助项目 40 1 75 0 0 1;中国科学院大气物理研究所创新基金领域前沿项目 8 460 5资助

摘　　要：利用改进的三维完全弹性强对流云模式 ,模拟了 1 998年 7月 2 1日晨发生在武汉附近的特大暴雨个例 ,结果显示 ,该模式模拟得到的降雨量与实测接近 ,计算得到的雷达回波强度最大值也与实际观测相一致 ,说明该模式对实际对流性强降水具有较好的模拟能力。在此基础上 ,通过冷云和暖云两种不同情况的比较分析 ,研究了云微物理过程在强降水形成过程中的作用。模拟结果表明 ,详细云物理过程的考虑对深入理解武汉这次强降水的形成过程是有意义的。该个例雨水的形成主要是暖雨过程 ,冰相微物理过程对该对流性强降水过程的发展和演变有重要的促进作用。在形成雨水的冷相过程中 ,霰的融化及其在 0℃层下碰并云水形成雨水的过程是主要的。模式云在 0℃层附近存在明显的雷达回波亮带 ,亮带中间含有强回波核和及地下挂回波。分析表明 ,这种强回波核和下挂回波的产生主要是由于冰相粒子在 0℃层融化形成的 ,融化的冰相粒子与云滴碰并又加速雨水的产生。在这些融化的冰相粒子中 ,贡献最大的是霰粒。文中还分析了该强降水暴雨云维持长时间强降水的云物理机制。在低层大气温暖高湿和环境风切变有利条件下 ,倾斜上升气流和下沉气流之间的准稳态结构可能是暴雨强降水得以长时间维持的重要原因。A three dimensional numerical model of severe convective rainstorms is developed and used to evaluate its stability and validity on the case study of the torrential rainstorm occurring in Wuhan, Hubei Province, on the morning of 21 July 1998. The modeling results show that the model successfully simulates maximum 10 minutely rainfall and maximum hourly rainfall, which are very close to the observed maximum 10 minutely rainfall of 22 mm and maximum hourly rainfall of 107 6 mm at Hankou Weather Station of Wuhan on this morning. The domain maximum radar reflectivity derived from the simulated total rainwater mixing ratio fields is also in good agreement with observations. The comparisons indicate that the model has an ability to well simulate the extremely and successive heavy rain. The model results also indicate that the consideration of detailed cloud physical processes is significant for further understanding the formation of this heavy rainfall event. The warm cloud process was the main developing process in the rain formation of this event, but the ice phase microphysical processes can greatly speed the rain formation. The vertical distributions of simulated radar reflectivity show that the stronger radar echoes appear mainly in the zones from the 0 ℃ level to the ground. A bright band echo exists inhomogeneously in the zone from the 0 ℃ level to 2 km range low to the level. Some strong cores with echo intensity of >50 dB Z are involved in the bright band. The overhang echoes from the strong cores come into existence and reach the ground following with time. The further analysis shows that the strong echo cores and their hang echoes are resulted from melting of ice phase particles in the 0 ℃ level. The melting particles collecting with cloud drops further increase the production of raindrops. In this simulation the graupel particles contribute the highest to the melting ice phase particles. In the last part of this paper an analysis from cloud physics shows that this kind of severe convective

关 键 词：强降水 云物理过程 三维数值模拟 对流云 雷达回波亮带 

分 类 号：P426.51[天文地球—大气科学及气象学]