A vigorous, westerly flow of air in the upper and middle troposphere over mid-latitudes. Frauenfeld and Davis (2003) J. Geophys. Res. 108 think the Northern Hemisphere circumpolar vortex could be a good indicator of climate change. ‘During the summer–fall season, the trend towards stronger circumpolar flow [in the Southern Hemisphere] has contributed substantially to the observed warming over the Antarctic Peninsula and Patagonia, and to the cooling over eastern Antarctica and the Antarctic plateau’ (Thompson and Solomon (2002) Science 296).
Subjects: earth sciences and geography.