The Influence of the Polar Night Jet on the Tropospheric Circulation in a GCM

Abstract

The influence of the polar night jet structure in determining the wave properties in the troposphere is examined using a general circulation model (GCM). It is shown that there are significant differences in the tropospheric simulation when the polar night jet is changed. Planetary wave theory leads us to expect that this will be the case for the stationary planetary waves; however, the changes found here extend to the transient eddies as well and to all scales in the model. The degree of trapping of the planetary waves in the troposphere is determined by the strength and structure of the polar night jet, resulting in the sensitivity of the troposphere to that structure. The most significant changes in the height field occur at high latitudes, beneath the polar night jet, but significant changes in the heat and momentum fluxes take place at both middle and high latitudes. The results indicate that inaccuracies in the stratospheric simulations of any general circulation model will produce serious errors in the planetary waves and therefore in the general eddy properties of the model.