Development of a new global forecast system in CMA

Since 2007, a new global NWP system-GRAPES_GFS (GRAPES Global Forecast System) has been being developed in China Meteorological Administration (CMA). The GRAPES_GFS is based upon the GRAPES global model and global 3-DVAR system. To develop the GRAPES_GFS, the GRAPES global model has been carefully tuned to better represent the global mass balance, cloud distribution and general circulations. Much more efforts have been made in satellite radiance data assimilation in GRAPES_3DVAR. At present, the GRAPES_GFS is at the pre-operational test, and shows rather encouraging forecast performance. The configuration of GRAPES_GFS is 0.5°x0.5°in horizontal and 36 levels in vertical with the model top at 10hPa, and the assimilation is conducted at the standard pressure levels with the 1.125°x1.125°horizontal resolution. The model physics package includes RRTMG short/long wave radiation, simplified Arakawa-Schubert cumulus and WSM-6 microphysics, CoLM land model, nonlocal PBL(Hong and Pan, 1996) and gravity wave drag (McFarlane, 1987). Satellite radiance data possess about 50% of all the assimilated observations.