尺度适应的对流参数化方案对一次华南飑线模拟的影响

The Impact of Scale-Aware Cumulus Parameterization Scheme on the Numerical Simulation of a Squall Line in South China

尺度适应(scale-aware)的物理过程是现代数值预报发展的一种趋势,本文针对GRAPES_Meso(Global/Regional Assimilation and Prediction Enhanced System)模式没有考虑物理过程尺度适应的现状,首先在KFeta(Kain-Fritsch Eta)积云对流参数化方案中引进了尺度适应过程,对该方案的对流时间尺度、格点垂直速度以及夹卷率进行了基于尺度适应参数化的改进。为研究尺度适应KFeta方案与原KFeta方案对不同分辨率模式模拟结果的影响,选取了一次华南飑线过程进行数值模拟和影响分析。结果表明:在3 km、5 km、10 km、20 km水平分辨率的GRAPES_Meso模式中,尺度适应KFeta方案相比原方案,对降水强度及落区分布的模拟有一定的正效果,随着模式水平分辨率提高,次网格降水减少、格点降水增多、对流层中低层夹卷略有增强,对原来存在的对流层高层及低层偏冷的偏差有一定的改进,对流活跃区域的上升气流强度、云中水凝物含量更符合真实的天气系统演变。综合来看,改进后的方案更适用于高分辨率数值预报模式,该研究结果可以为尺度适应对流参数化方案的应用及数值模式强降水预报性能的优化提供有益的参考。

The scale-aware physical process is one of the commonly used methods of modern numerical weather prediction.Considering that Global/Regional Assimilation and Prediction Enhanced System(GRAPES_Meso)model did not included this scale-aware physical process,this paper is among the first to introduce the scale-aware parameterization in the Kain–Fritsch Eta(KFeta)convective parameterization scheme.The convective time scale,grid vertical velocity,and entrainment rate of the scheme are improved on the basis of the scale-aware parameterization.In order to analyze its effects on the simulation results by the scale-aware scheme and the original scheme in different resolution models,a squall line in South China was selected.The results showed that in the GRAPES_Meso model with the horizontal resolutions of 3 km,5 km,10 km,and 20 km,the scale-aware KFeta scheme displayed certain positive effects on the simulation of precipitation intensity and location.With the increase of model resolution,there was a decrease in sub-grid precipitation and an increase in the grid precipitation.The entrainment rates in the tropospheric middle and low layers were slightly enhanced,while the existing cold deviations have shown some improvements.The intensity of updraft and the hydrometeors’content in the strong convection area are more consistent with the real atmospheric conditions.Overall,the modified scheme is more suitable for the high-resolution numerical weather prediction model.The results of this study can provide a useful reference for the application of scale-aware convective parameterization scheme and the optimization of strong precipitation forecasting performance in the numerical weather prediction models.