New Version of the CMA-GFS Dynamical Core Based on the Predictor–Corrector Time Integration Scheme

The operational numerical weather prediction system established by the China Meteorological Administration (CMA), based on the Global/Regional Assimilation and Prediction System (GRAPES) model, adopts the classical semi-implicit semi-Lagrangian (SISL) time integration algorithm. This paper describes a major upgrade to the dynamical core of the CMA global forecast system (CMA-GFS), which was successfully incorporated into operation in 2020. In the upgrade, the classical SISL is further developed into a predictor–corrector scheme, a three-dimensional (3D) reference profile instead of the original isothermal reference profile is applied when implementing the semi-implicit algorithm, and a hybrid terrain-following vertical coordinate system is also applied. The new version of the dynamical core greatly improves the model performance, the time integration reaches second-order accuracy, the time step can be extended by 50%, and the efficiency is greatly improved (by approximately 30%). Atmospheric circulation simulation is systematically improved, and deviations in temperature, wind, and humidity are reduced. The new version of the dynamical core provides a solid foundation for further development of the entire operational system of the CMA.