Description of the JMA Operational Spectral Model

Abstract

A 12-level hemispheric spectral model has been developed for operational purpose. The model has a horizontal resolution of triangular 42 truncation and incorporates full physical processes including diurnal variation of shortwave radiation and cloud effects. The model has been tested for nearly a year before introduction as an operational model, and compared with the grid point model which was operational at that time. It has been shown that the spectral model was superior to the grid point model in many respects. The reason is due to various factors, i.e., higher resolution, initialization, analysis etc., and not just due to the use of the spectral method. The useful predictability of the spectral model is found to be 5-6 days. The model forecast is quite useful in predicting sudden developments of baroclinic disturbances, typhoon movements and other important meteorological phenomena with reasonable accuracy.