In June 2020, the China Meteorological Administration (CMA) began operation of an upgraded global NWP system GRAPES_GFS V3.0. The upgrade brought major improvements as follows:

1.      Dynamical frame

The prediction-correction SISL time integration algorithm and 3-D reference profile were developed to address the problem of computation accuracy. In addition, new tangent-linear and adjoint modelsof 4D-Var system were developed.

2.      Vertical layers

The pressure of the top level was raised to 0.1 hPa to facilitate the application of analysis and forecast at high-level. Moreover, the nonorographic gravity wave drag parameterization was introduced which is essential to forecasts in the stratosphere.

3.      Data assimilation

The radiation transfer model in the data assimilation system was improved. In addition, increased upper satellite channels were assimilated.

Verifications were conducted to compare performances of the previous and upgraded systems for one-year hindcast and more than one-month parallel runs. Forecasts and data assimilation are improved overall. In particular, precipitation forecasts in medium range were improved and the forecast skills for subtropical high in summer and polar vortex in winter were better than the old version. The new system also led to substantial improvements in prediction in the stratosphere.

In summary, the implementation of GRAPES_GFS V3.0 will not only improve the calculation accuracy and forecast skill but also help to better support the operations at CMA.