一η模式中高分辨边界层方案及对降水影响的数值试验

Numerical Simulation of High Resolution PBL Scheme in An η Model and Its Influence on Precipitation

利用16层垂直不等距中尺度η模式,引入高分辨边界层湍流闭合方案,且将垂直分层加密至21层。将改进后的模式用于边界层过程的模拟,结果表明,改进后的模式能较好地模拟出边界层的日变化过程及边界层结构;通过对暴雨个例的数值模拟,发现改进后的模式对降水预报的TS评分,特别是暴雨TS评分有明显提高;最后对边界层过程影响暴雨的机制进行了简单的探讨。试验表明,地表潜热通量结合低空急流的水平输送是夏季切变线和准静止锋这一类强降水形成的主要原因之一。

Using the 16-layer mesoscale ETA model with defferent interval layers, the high resolution PBL scheme is introduced into this paper, and the vertical layer numbers have been increased to 21. Experiments show that the improved model can simulate the daily variation and the structure of the boundary layer more finely. The numerical simulation of heavy rain shows that the improved model to TS grade of precipitation is obviously higher than the former model, especially in the TS grade of heavy rain. The mechanism about PBL process influencing on heavy rain is simply discussed. The numerical experiments show that the integrating of surface flux formed horizontal transfer of lower tropospheric jet is one main reason of the severe precipitation with shear line or quasi-stationary front in summer.