During the 9th Five-Year National Development Plan period, in collaboration with the Institute of Atmospheric Physics, Chinese Academy of Science and other institutions, NCC developed a middle resolution global atmospheric model,BCC_AGCM1.0. The original version of the model was the medium-range NWP model at NMC, which could be traced back to ECMWF Cray-based model (1998). Horizontally, it selects 63 waves through triangle truncation (approximately 1.875 x 1.875 degrees). It has 16 layers (25hPa at the top, and 996hPa at the bottom) with hybrid P-σ vertical coordinates (η). Its time-step length is 22.5 minutes. This model takes into account physical processes like topography, radiation, large-scale precipitation, convections, evaporation, condensation, boundary layer process, land surface process, and so on. A semi-implicit time-step integration scheme is adopted in solving the equations.
In the development process, the following modifications have been made on original medium-range NWP model including its dynamic framework and parameterization schemes.
(1) A reference-atmospheric scheme and a mass-conservation scheme have been inserted into it.
(2) A progressive recurrent correction method is adopted so as to solve the problem of negative moisture content in the initial fields.
(3) The improved semi-Lagrange method provides a higher accuracy in calculation of water vapour transportation.
(4) Morcrette scheme and k-distributive radiation scheme is introduced into the model.
(5) The original Kuo’s convective parameterization scheme is replaced by the mass flux scheme developed by Gregory.
(6) Major modifications have been made on the surface processes, e.g. coupling with Dickenson’s BATS and Sun’s 3-layer snow model.
(7) The propagation of gravity wave blockages and boundary conditions have been improved in terms of better description of near surface processes.
(8) The parallel version of BCC_AGCM1.0 was released at the same time.
The BCC_AGCM1.0 has undergone 20-year hindcast experiments and it has been tested using the sea temperature and sea-ice conditions as specified by AMIP-II. The results demonstrate that this model has comparatively good performance in climate modeling and prediction. Now, this model has been applied to the following aspects:
(1) Operational monthly extended forecasts;
(2) Monthly, seasonal and annual predictions with a coupled ocean model;
(3) Climate change simulations with different IPCC greenhouse gas emission scenarios;
(4) Research on climate variability at different time scales.
BCC-AGCM 1.0 T63L16 AMIP2 Results
1, Line Plots of zonal means
2, Horizontal contour plots
3, Horizontal contour plots of differences
4, Vertical contour plots of zonal means
5, Vertical contour plots of zonal mean differences