Abstract

The Polar-night Jet Oscillation (PJO) has been described by Kuroda and Kodera as a mode of intra-seasonal variability of the Arctic Polar-night Jet, in which wind and temperature anomalies migrate poleward from the tropics in the upper stratosphere, then downward to the lower stratosphere over a timescale of several months. This mode has been strongly implicated in one pathway for solar variability to influence tropospheric climate. In the first part of this talk I will argue that the most coherent manifestation of the PJO is during extremely large amplitude events following a subset of major sudden stratospheric warmings, and that the dynamics of the anomalies’ descent can be well understood in terms of the structure of radiative timescales and the filtering of gravity waves.

In the second part of the talk I will demonstrate the relevance of these ‘PJO events’ to stratosphere-troposphere coupling in a series of careful experiments with the Canadian Middle Atmosphere Model, a comprehensive, stratosphere-resolving model.