全球大尺度信息在3 km GRAPES-RAFS系统中的应用

为了缓解快速分析预报循环过程中固定边界条件造成的预报锁定，缩短动力、热力调整时间，提高模式预报能力，全球模式产品的大尺度部分的信息被引入GRAPES-RAFS系统中，通过二维离散余弦变换方法对全球模式产品和区域分析进行谱分解，获得综合全球大尺度和区域中小尺度信息的混合尺度分析。通过2018年5月9日—6月9日1个月间歇分析预报循环，比较对照试验和混合尺度分析试验的冷启动和暖启动预报结果表明，在快速分析预报循环中，全球大尺度信息的加入不仅增加分析的大尺度部分信息和降低地面气压倾向，缩短模式预报的动力、热力调整时间，且地面要素场、分析场和降水的暖启动预报质量有显著提高；台风艾云尼路径预报也更加接近观测。另外，GRAPES-RAFS循环的暖启动与冷启动预报相比，初始场更加协调，但地面2 m气温和10 m风场的预报质量比冷启动预报差，且其ETS降水评分也明显低于冷启动预报。混合尺度方案在RAFS系统中的应用能有效提高初始场的协调性，地面、高空要素和降水预报质量得到提升。 

Application of global large scale information to GRAEPS RAFS system

To alleviate the problem caused by fixed boundary condition in the GRAPES-RAFS system and improve the forecast qualities of regional model, a blending method to merge large scale information of global model with meso-scale information of regional analysis is implemented in the GRAPES-RAFS system using Discrete Cosine Transform (DCT) filter. During 9 May to 9 June 2018, the forecast qualities between the control experiments of the cold-start and experiments of warm-up initialization and the blending scale analysis by the GRAPES-RAFS are compared. The numerical results indicate that the large scale information and variables'' harmony of analyses increase, and the spin-up time is decreased with the global information and analysis in GRAPES-RAFS at 3 h intervals merged. The forecast quality of surface variables, analysis and precipitation with warm-start has been obviously improved. In addition, the simulated track of typhoon Ewiniar is much closer to observation by using the blending analysis. The warm-up initial physical fields, which lead to far smaller surface pressure tendency, are more harmonic than those of cold-start initialization. However, it is observed that the warm-up forecast quality of 2 m temperature and 10 m wind is not better than that of the cold-start, and that the warm-up precipitation score of ETS is lower than that of the cold-start as well.