模式垂直分辨率对梅雨锋暴雨数值模拟的影响

利用中尺度数值模式MM5(V3),对2003年7月7日~8日发生在武汉地区的一次梅雨锋暴雨过程进行了数值模拟。采用经过简化处理的基于矢量模的双参数最优化处理方法,对模式大气进行了垂直分层。在水平分辨率不变的情况下,数值模式的垂直分层分别采用25层和36层进行了对比模拟试验。模拟结果表明,水平分辨率达到较高的精度后,粗的垂直分辨率会放大模式中地形的作用,造成数值模拟雨带落区的偏差;要得到比较好的模拟结果,需要相应的提高数值模式的垂直分辨率。水平分辨率与垂直分辨率的不协调,会在水平方向上产生虚假的重力波,影响数值模式的模拟结果。

THE EFFECTS OF MODEL VERTICAL RESOLUTION ON THE SIMULATION OF TORRENTIAL STORM OVER MEIYU FRONT

In this paper,a torrential rainfall on Meiyu front during July 7~8,2003 is simulated by use of the non-hydrostatic meso-scale model MM5(V3).Two-parameter nonlinear optimization procedure based on given vector norm is employed in model vertical resolution selection.With the high horizontal resolution,numerical simulations with 25 and 36 vertical layers are conducted,respectively.The results show that,with a high horizontal resolution,the coarse vertical resolution may magnify the effects of meso-scale topography,which will cause the discrepancy in the rain belt simulation,with a higher resolution vertically,the results could be improved.The effects of spurious gravity waves due to the inconsistency of the vertical and horizontal resolution are also discussed.