【作者】 于翡；

【导师】 姚展予；

【作者基本信息】 中国气象科学研究院 ， 大气物理学与大气环境， 2009， 硕士

【摘要】 积层混合云降水是环北京地区降水的一种主要类型。观测显示,积层混合云有自己独特的动力热力结构,降水过程也有自己的特点。深入探讨环北京地区积层混合云降水发展的动力和微物理机制不仅有利于提高对该类型降水的预报预测水平,也能为人工影响天气工作提供理论支持。本文主要分四部分内容:第一部分系统地回顾了近些年来对积层混合云降水的研究,指出目前存在及待解决的问题;第二部分简要介绍WRF-ARW模式主体及其采用的积云参数化方案和云微物理参数化方案;第三部分结合实测资料对2007年9月28日发生在环北京地区的一次切变线天气系统造成的积层混合云降水过程进行了WRF-ARW实例模拟结果的分析和冰相微物理过程敏感性试验结果的分析,重点讨论了切变线积层混合云系发展的动力、热力条件和微物理结构特征;第四部分结合实测资料对2008年10月4日发生在环北京地区的一次低涡天气系统造成的积层混合云降水过程进行了WRF-ARW实例模拟结果的分析和冰相微物理过程敏感性试验结果的分析,重点讨论了低涡积层混合云系发展的动力、热力条件和微物理结构特征。通过对两个个例的分析发现,切变线和低涡形成积层混合云降水云系均在高空西风气流的引导下向东移动并减弱层化直至消散;WRF-ARW中尺度模式较好地模拟出来两个个例的降水过程;实例模拟结果说明,积层混合云降水分布不均匀,雨区中存在多个强降水中心,云系中微物理量在水平和垂直方向上分布都不均匀,层状云内的冰晶、雪、霰、云水含量相对较少;而对流云团中高层十公里左右存在冰晶大值区,云水含量也非常丰富,降水物理过程中,此次积层混合云不仅具有对流云和层状云形态混合的特征,还具有冷雨过程和暖雨过程共存的相态混合的特征;与暴雨过程中的积层混合云系不同,这两个个例研究的降水过程中,对流不稳定能量并不大,中层的大范围辐合和相应的较均匀上升气流场支撑着层状云,而在均匀上升气流场中的波动导致了对流云镶嵌其中,浮力与惯性力共同作用的中尺度条件对称不稳定可能是积层混合云系形成和维持的主要机制。通过比较分析采用暖雨过程微物理方案和冷雨微物理方案的模拟结果发现,当忽略冰相微物理过程时,虽然也能模拟出较接近实际的积层混合云的热力、动力特征及形态特点,但均匀上升气流场中的波动较小,对流云部分较弱,层状云部分云厚较大而水平范围较大。可能的原因是冰相微物理过程通过释放的冻结潜热以及播撒-供应机制使更多的过冷水凝结释放凝结潜热来为对流云的发展提供更多的能量,使对流云发展更旺盛,维持时间更长,产生更多降水,减缓层化过程,延长积层混合云的生命史。更多还原

【Abstract】 The complex system of the stratiform and embedded convective percipitation is a main rainfall source over Beijing and adjacent regions one of the main weather systems over northeastern China. Observation shows that the complex system of stratiform and embedded convective percipitation has its own unique thermal and dynamic structure, the precipitation process has its own characteristics The studies of this type of cloud and precipitation are very useful to enhance the forecasting level, and also helpful to support the research and operation of weather modification.This paper conclude four parts: first part gives the review of The complex system of the stratiform clouds and embedded convective clouds, and point out the urgent issues to be solved. Then, the second part gives an introduce of the WRF-ARW model, especially the cumulus parameterization scheme and microphysics parameterization scheme. Basing on the issues mentioned in the first part, the third part shows a thermo-dynamic structure and microphysical characteristics study on one case of a complex system of the stratiform and embedded convective percipitation on September, 28, 2007, and forth part shows the other study on the case on October,4,2008. Both the two cases are analyzed by using encrypt ground-observing data, radar data, satellite data, and real simulation results from WRF-ARW, and sensitivity experiments about ice-phase microphysical processes are also applied to the two cases.The main results shows that, the clouds are weakened by the shear line, the formation of stratiform cloud development. It is also reveals that the complex of stratiform clouds and embedded convective clouds is not only the complex of clouds with different shapes, but also the complex of different microphysical processes. And the large-scale convergence on the middle level and the corresponding uniform updraft develop the stratiform clouds, while the dramatic fluctuations of updraft lead to embedded convective clouds, which may be conducted by conditional symmetric instability. The ice phase microphysical processes make the complex system of the stratiform and embedded convective precipitation a long life.更多还原