Quasi-geostrophic simulations of the 1979 stratospheric major warming: The importance of middle-atmospheric drag

Abstract

A detailed test of a simple nonlinear quasi-geostrophic model of stratospheric sudden warming has been performed. The model is of Matsuno's type, which includes only the interaction between a single planetary wave and the zonal mean flow. Given this limitation, the 1979 major stratospheric sudden warming has been employed to test the ability of the model to simulate an actual warming event. This event proved to be an especially appropriate testing ground for the model, since its main assumptions were reasonably well satisfied by the observational evidence. Results from the model simulations demonstrate (a) that such simple quasi-geostrophic dynamics are completely capable of providing a rather detailed simulation of the 1979 major warming event and (b) that the ability of the model to simulate successfully the observed evolution of the warming is extremely sensitive to the magnitude and form of the dissipation mechanism that is assumed to operate in the middle atmosphere.