An Illustrative Model of Seasonal and Interannual Variations of the Stratospheric Circulation

Abstract

A simple wave-zonal flow interaction model, originally developed by Holton and Mass, is used to illustrate a rudimentary conception of seasonal and interannual variations of the stratospheric circulation. The radiative heating is varied periodically with an annual component to investigate the response of the circulation (i.e., the seasonal variation) to the periodic forcing. The response is qualitatively different depending on the wave forcing from the troposphere. The difference resembles that of the climatological seasonal march between the Northern and the Southern hemispheres. No example of interannual variations (namely, nonperiodic responses) was obtained for the periodic annual forcing. Interannual variation of external conditions is necessary in the present model to obtain interannual variations. A finite range of year-to-year variations of the wave forcing can produce large interannual variability as in the Northern Hemisphere.