The Japan Meteorological Agency (JMA) is operating the Global Spectral Model (GSM) for the short- and medium-range forecast up to nine days ahead to cover the entire globe. JMA enhanced the spatial resolution of GSM from the previous TL319L40 (approximately 60km in the horizontal and 40 layers up to 0.4 hPa in the vertical) to TL959L60 (approximately 20km in the horizontal and 60 layers up to 0.1 hPa in the vertical) in November 2007. A new convective triggering scheme was also introduced into the deep convection parameterization to improve the precipitation forecast. In August 2008, JMA implemented a new dynamical core (reduced Gaussian grid) in GSM and number of grid points in calculation of nonlinear terms was reduced.
The major features of GSM will be discribed as well as some forecast test results comparing the performance of current and previous GSM.