Introduction of GRAPES dynamic core

GRAPES is a short form of Global/Regional Assimilation and PrEdiction System which is a new generation of unified model of operational Numerical Weather Prediction (NWP) system in China Meteorological Administration (CMA). This paper will give a general introduction to the dynamic core of GRAPES. The dynamic core was characterized by (1) semi-implicit and semi-Lagrangian scheme for time and space discretization (A. Staniforth and J. Cote, 1991; Qian et al. 1998); (2) latitude- longitude grid system; (3) regional and global unified model; (4)non-hydrostatical and full compressible; (5) Arakawa-C staggered grid for horizontal arrangement, particularly with v wind component in poles;(6)Charney-Phillips vertical level arrangement; (7) Height terrain-following vertical coordinate (Gal-Chen and Somerville, 1975 ); (8) PRM (Piecewise Rational Method, Xiao and Peng, 2004) used for conservative and positive advection with convexity preserving of specific humidity. The detailed descriptions of GRAPES could be found in Chen et al. (2008), Xue and Chen (2008). The key project for development of GRAPES has been launched in 2001. The regional versions of GRAPES have been operationally implemented since 2004 at the national and regional meteorological centers of CMA. And the global version of GRAPES has been quasi-operationally implemented since 2009 at NMC/CMA.