Improvements and Performances of the Operational GRAPES_GFS 3DVar System

In recent years,the capability and stability of GRAPES(Global/Regional Assimilation and PrEdiction System) three-dimensional variation data assimilation system(3DVar) is upgraded and improved gradually in Numerical Weather Prediction Center of China Meteorological Administration.Improvements in analysis scheme and assimilating data technique for GRAPES 3DVar in the past two years are overviewed.Then the capability and performance of G-M3DVar latest version are evaluated by two-year length experiments.The accuracy and precision of G-M3DVar analyses is evaluated against radiosonde observation and ERA-Interim reanalysis and is compared with NCEP FNL and T639 analysis.Taken radiosonde data as a reference,the root mean square error and bias of pressure analyses of GM3DVar are smaller than ERA-Interim reanalysis and NCEP FNL analysis data in all domains in both winter and summer seasons.The root mean square error and bias of u wind analysis of G-M3DVar are larger than ERA-Interim reanalysis and NCEP FNL analysis in