【摘要】 在对2004年5月底华南前汛期一次大暴雨过程中尺度数值模拟的基础上,研究了形成大暴雨的中小尺度系统演变的物理机制与环境场条件。结果表明:前汛期的锋面兼有温度和湿度梯度;东北至日本海有较深的冷槽,长江中游有低涡生成发展,并与暖切变相联,有利于中尺度系统不断生成;深厚的中低层辐合层和较高的无辐散层为飑线产生提供了有利的上升运动条件,与中空槽相伴的强风核处于槽底以西,槽前强辐合成为飑线产生的关键;除孟加拉湾主要提供暴雨产生的水汽外,西太平洋和南海也向华南至江南地区输送水汽;夏季风强盛和副高加强导致雨带位置偏北;暴雨前水汽场变化的信息要早于涡度、散度、垂直速度场。更多还原

【Abstract】 After diagnosing and analyzing the heavy rainstormoccurring on 30 May,2004,which is infrequent when the rain belt moves towards the north in the South China in the pre-flood season through the meteorological dynamics,the mesoscale numerical simulation method is applied to analyze the heavy rainstorm.By researching the macroscale circumfluence and the meso- and micro-scale system′s physical mechanisms and the environment conditions,the main results are obtained.The front of the pre-flood season has the gradients of temperature and humidity at the same time.There was the deeper and cold trough from the northwestern China to the Japan Sea.The low vortex develops in the middle reach of the Yangtze River and it is also related withthe warm shear-line,which is in favor of forming the mesoscale system.The thick non-divergence level and the convergence in the medium-level offers the advantageous conditions to the birth of squall line.The core of the strong wind locates to the west of the hollow trough which makes the convergence in front of the trough,which is the key to generate the squall line.The BangladeshGulf,the West Pacific andSouth China Sea are all the sources of the water vapor which make such the heavy rainstorm.The strong summer wind and the enhancement of the subtropical high pressure lead to the rain belt locating partial north.The occurrenceof the sensitivity of water vapor to the torrential rain is ahead of the vorticity,divergence and the vertical speed,et al.更多还原