一个有限区域中尺度模式的设计及预报试验

THE DESIGN OF A MESO SCALE NWP MODEL AND PREDICTION EXPERIMENTS

关键词:  中尺度模式  设计  预报试验

Key words:  Meso scale model  Design  Prediction experiment

摘要:

以一个6层原始方程模式的基本动力学框架为基础,设计了一个对物理过程考虑得较全面的中尺度原始方程模式。该模式采用(x,y,σ)坐标系；大气上界取为10hPa,提供多种水平边界条件；水平和垂直分辨率均可调；降水方案包括大尺度降水和深厚积云对流降水；地面温度的计算采用地面热量收支方程；考虑了地气和海气交换作用；垂直交换系数的计算采用Liouis格式；水平扩散采用二阶形式和四阶形式相结合的方案,扩散系数是网格点位置和风场的函数；积分方案采用经济的中央差格式。在水平格距取80km,垂直方向不等距地分为16层的分辨率条件下,利用该模式进行逐个个例预报试验。结果表明,模式计算稳定,能较好地报出主要的天气形势,预报的降水也较接近实际。文中给出了一些检验指标的统计结果。还在预报能力及模式特性方面与原6层模式进行了对比。

Abstract:

Based on the basic dynamic frame of an operational model(KMM 3),a new meso scale NWP model with good considerations of many physical processes is designed.In the model,(x,y,σ) coordinates system is used,several boundary arrangements are supplied and model resolution can be chosen with ease.The precipitation includes contributions of both large scale process and deep convective process.Ground surface temperature is computed from surface energy budget equation.The exchanges between ground and atmosphere and from ocean to atmosphere are considered.The drag coefficients are calculated with liouis scheme and the exchange coefficients in PBL are calcuated with a scheme similar to that of Liouiss.Two types of horizontal diffusion scheme,the second order form and the fourth order form,are used here.The model is integrated with an economical time differencing system.With 80 kilometers taken as the mesh interval and model atmosphere divided into 16 layers,26 prediction experiments are made.The results show that,the model runs stably with good efficiency,well predicting the main resovable meso scale systems and large scale patterns and the precipitation predicted is close to the real case.