非静力平衡模式的中尺度非均匀初始场试验和锋面模拟
TEST OF NON-HYDROSTATIC MODEL BY USING MESOSCALE NON-HOMOGENEOUS INITIAL FIELDS AND SIMULATION OF FRONT CASE
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摘要: 用非静力平衡二维中β-γ尺度大气模式,选取1987年欧洲的一次冷锋过程为个例,以法国的静力平衡模式的模拟结果为初始场,选用5km,25km,45km3种水平格距进行了水平范围为2000km的模拟,结果表明:(1)中尺度非静力平衡模式应用非均匀初始场,而不加人为的初始扰动是可行的;(2)扰动量的初始场中π'的精度要求很高,应严格符合静力平衡条件,否则就会产生严重误差,甚至在一个时步内改变垂直速度;(3)5km,25km,45km3种格距的对比模拟表明,5km格距的非静力平衡模式能模拟出锋面上的多个中β尺度对流,且垂直速度场分布与实际最接近,而后两种格距只能模拟出锋面上的大范围上升区,不能细致地描述锋面对流结构。Abstract: Two-dimension non-hydrostatic β-γ meso scale atmospheric model is used to simulate an European cold frontal process in 1987,whose initial fields come from a hydro-static model.The horizontal extension is 2000 km and three different horizontal resolutions 5 km,25 km,and 45 kmare used.The results show:1) It is practical fora meso scale non-hydrostatic model to use non-homogeneous initial fields,withoutan artificial disturbance celladded.2) The initial fields of the distur bed quantity (pressure π'), should fo llow s the principle of hydrostatic balance strictly,other wise it can consul tin greatacceleration,so far as to change the vertical velocity field completely in a shorttime step.3) Non-hydrostatic model with grid length of 5 km can getseveral meso scale convective cells on the front,and the distribution of vertical velocity are similar to the reality,while the model with largerresolutions (25 kmand 45 km) can only describe a wide updraftasso ciated with front.