Abstract
Results are presented from a numerical simulation of the stratospheric circulation using a spectral general circulation model of the Meteorological Research Institute. The model has 23 layers in the vertical extending from the surface to approximately 70km in the middle mesosphere and uses the spectral transform method with a rhomboidal 13 truncation. The model includes all major physical processes as well as realistic radiative transfer. The model also includes Rayleigh damping as a parameterization of gravity wave breaking. The model has been run for two years, and the results are compared with observations.
The model generally simulates the overall stratospheric fields of temperature and winds reasonably well. Seasonal variations of the stratospheric fields are also successfully reproduced. Successful aspects of the current simulation include: clear separation of the subtropical and polar night jet streams; stratospheric summer easterlies of the proper speed and extent; interhemispheric differences in the stratospheric circulation; major and minor sudden warming events; and an equatorial semi-annual oscillation. Obviously deficient results include: excessively cold polar night vortices; and much less westerly winds in the equatorial semi-annual oscillation.
A simulated final warming in the Northern Hemisphere and a minor warming in the Southern Hemisphere are briefly described, along with the evolution of easterlies from late-winter to spring.
