太行山地形对华北暴雨影响的数值模拟试验

利用高分辨率区域气候模式RegCM3对华北地区1996年夏季降水进行了数值模拟,对照中国台站的实测资料,对模拟的夏季降水量日变化特征进行了比较,在此基础上,设计了太行山地形敏感性试验,模拟了太行山脉地形高度变化对1996年夏季发生在华北地区的3次典型暴雨过程的影响.研究结果认为,RegCM3模式能够较好地模拟1996年夏季华北地区雨带位置及主要降水过程,对3次典型暴雨过程中暴雨中心的落区及位置移动均有较好的表现,不足的是模拟的降水量偏大.地形敏感性试验结果发现,太行山地形对华北暴雨天气过程有着重要影响,但是对于不同型态的暴雨过程,地形的影响有不同表现.对于太行山区型暴雨,太行山地形的阻挡和抬升作用导致迎风坡和背风坡降水增加,而去掉地形后太行山两侧降水明显减少;对于回流型暴雨,降水系统从东北地区南部向西南方向移动,低层气流主要为偏东型气流,地形的存在对于降水系统的西移速度及降水落区均有重要影响,去掉地形后太行山东侧降水明显减少;对于东移型暴雨,降水从太行山南麓向东北方向移动,太行山脉对于环流形势的影响并不明显,因而仅影响降水强度,对降水位置影响不大.

Numerical simulation for terrain effects of Taihang Mountain on heavy rainfall over North China

Summer rainfalls over North China in 1996 are simulated using regional climate model (RegCM3), and the simulation results are compared with the observed precipitations to investigate the model''s capability to reproduce the daily variation of summer rainfall.Based on that, the terrain effects of Taihang Mountain on three heavy rainfall processes over North China have been investigated by orographic sensitive experiment.Results show that the model can reproduce the spatial distribution of the summer rainfall, which are consistent with the observations in aspects of location and shift of the rainfall belt during three typical heavy rainfall processes.But the model overestimates the quantity of the rainfalls.The orographic sensitive experiments indicate that the topography of Taihang Mountain plays significant but different roles in the three events of heavy rainfall.When the rainstorm mainly occurred over Taihang Mountain, easterly flow is resisted and lifted by the mountain, therefore increase the rainfall over the two slopes of Taihang Mountain;while the rainfall obviously decrease on both sides should the mountain removed.For the returning-flow rainstorm type, the topography significantly influences both the location and westward movement of the rainfall.While for the eastward moving rainstorm type, the topography only changes the intensity of rainfall but has little influence on the rainstorm location and related circulations.