The Integration of a Low Order Spectral Form of the Primitive Meteorological Equations

Abstract

The interest for spectral forms of the meteorological equations has grown considerably over the past several years. Integrations in terms of spherical harmonics provide us with an interesting alternative to the grid point method. The results of an extension of the method to the complete meteorological equations will be presented here. A model based on five levels and 15 coefficients is integrated for 200 days starting from an atmosphere at rest and at a uniform temperature. The integration is then continued for another 22 days with 45 coefficients. Cross-sections show a jet stream in each hemisphere and low level easterlies along the equatorial belt. The amplitudes and the phase speeds of the planetary waves in the model compare favourably with their atmospheric equivalents. The results of this integration indicate that spherical harmonics could be used profitably in general circulation models or in the preparation of extended range forecasts. 1.