GRAPES地面风场同化方案研究

SURFACE WIND OBSERVATION DATA ASSIMILATION IN GRAPES

随着预报准确度要求以及同化分析循环周期的缩短,具有高时空分辨率的地面观测资料在同化系统中也越来越受到重视,而且一个好的资料同化系统应该能够给出模式近地面动力、热力和湿度状况的合理分析。利用GRAPES区域同化预报系统(GRAPES——Global and Regional Assimilation and Prediction Enhanced System),在近地层Monin_Obukhov相似理论的基础上,考虑了边界层的动力和湿热力约束,建立新的地面风场观测算子。将此新方案与目前GRAPES系统使用的三次样条插值的地面同化方案进行高度场预报试验、统计试验以及降水预报的TS评分比较,结果表明,加入新方案地面风场资料同化后,预报效果和对降水的预报能力都比旧方案有所提高。

With the advances of numerical weather simulation and reduced data assimilation updating cycle, surface observation data assimilation becomes more and more important in data assimilation systems, and a better data assimilation system should contain the restriction of thermodynamic processes in the surface layer. In this paper, a new surface wind observation operator is utilized in GRAPES_3DVAR, with the restriction of thermodynamic process in PBL. In order to research the ability of assimilation and forecast with new surface wind observation operators, some experiments are run using the GRAPES model. The major results indicate that the new method of surface wind observation operator has positive impact on forecast with GRAPES model.