Annual Cycle Integration of the NMC Medium-Range Forecasting (MRF) Model

Abstract

The NMC Global Spectral Model was integrated for one year. The model used is the same as the 1989 operational medium range forecast model except that the horizontal resolution was reduced from T80 to T40. Overall, the model was very successful in reproducing most of the characteristics of the atmospheric circulation and its seasonal evolution. A comparison with the summer and winter integrations of Kinter et al., which were performed with the NMC model operational in 1985, shows that the changes made in the last few years in the NMC model have significantly improved its ability to reproduce the atmospheric circulation, particularly in the tropics and in the summer hemisphere. The simulation of precipitation is also much more realistic with the present model. We also performed a 150 day simulation with a lower resolution (R16) version of the model. The stationary and transient eddy simulations were similar to that of T40 model but the zonal circulation was much poorer in the R16 model, particularly in the Southern Hemisphere. This indicates that for a global simulation study a horizontal resolution of at least T40 is necessary.