Enhanced-resolution Global Model - 13 December 2005

On 13 December 2005, starting with the 12 UTC run, the resolution of the Met Office global NWP model will be enhanced for the first time in six years. The model resolution is being enhanced both horizontally and vertically. The horizontal grid spacing of the model will be reduced from 60 to 40 km for a mid-latitude grid box (93 km to 63 km at the equator) and the number of vertical levels is increased from 38 to 50, with the additional 12 levels placed in the stratosphere (above 20 km). The vertical extent of the model is also increased with the top model level being raised from 38 to 65 km. Overall there is almost a factor three change in the total number of model grid points. This enhanced-resolution model makes use of the extra computing power afforded by the NEC SX8 supercomputer.

The main benefits from the increased vertical levels are improved use of satellite radiance data and reduced model biases in the stratosphere, Overall, there are consistent but modest improvements in performance measures for short-range forecasts (days 1-3). The reduced horizontal grid spacing gives systematically deeper, more-realistic tropical cyclones. The more-detailed orography at the new resolution should also mean more realism in local detail, as features such as the Rhone gap and Alpine barrier are now better represented.