Satellite climatological aspects of cold air mesocyclones in the Arctic and Antarctic

Cold air meso-scale cyclones occurring in the Arctic and Antarctic are compared in terms of their satellite-observed cloud vortex signatures, climatological regimes, and accompanying broadscale atmospheric and oceanic environments. Major similarities between the two polar regions include the occurrence of both single-banded ('comma cloud') and multi-banded ('spiraliform') mesocyclone cloud vortices; the preference for mesocyclones to occur in groups as 'outbreaks'; and their association with anomalies of the larger-scale atmospheric and upper ocean circulations, including the sea ice extent. Major differences between Arctic and Antarctic mesocyclones include the following: more frequent occurrences of the intense and deeply convective 'polar low' sub-type in the north polar region, where these systems may also be larger than their Southern Hemisphere counterparts; contrasts in the seasonal distributions of systems; and inferred differences in the dominant mechanisms initiating mesocyclone outbreaks at regional scales, particularly baroclinic instability, CISK (Conditional Instability of the Second Kind) and ASII (Air-Sea Interaction Instability). These differences are explained largely through consideration of the physical geography of the two higher latitude regions: their land-sea distributions, patterns of sea-ice and snowcover extent, and the extent of continental glacierization. There is a greater role apparent for topography and downslope (katabatic) winds in mesocyclone developments over ice-covered surfaces close to Antarctica; however, sea-air fluxes of heat and moisture are important for polar lows in the Arctic marginal seas.