Satellite Passive Sensing of the Marine Atmosphere Associated With Cold-Air Mesoscale Cyclones

Contemporary research into extratropical cloud systems optimizes the increase in resolution of visible (VIS) and thermal infra-red (IR) sensors, and the ability to retrieve wind and atmospheric moisture variables at mesoscales using microwave radiometry. These passively-acquired remote sensing data are used to develop synoptic climatological (conceptual and simple statistical) ‘models’ of mesoscale cyclones in cold-air outbreaks (mesocyclones, ‘polar lows’) occurring over the otherwise data-void southern oceans. Mesocyclones present a limitation to successful weather forecasting for New Zealand and coastal Chile, southern Australia and South Africa, during the cold season. The synoptic climatological analyses show that: 1) the patterns of mesocyclone cloud vortex origins, movement and dissipation (‘mesocyclone regimes’), exhibit spatial dependence and have associations with upper-ocean conditions; 2) mesocyclone ‘outbreaks’ are embedded within characteristic larger-scale anomaly fields of tropospheric pressure, height, and layer thickness (mean temperature); and 3) composite (statistical average) models of cloud system structure based on the microwave retrievals of marine weather reveal mesocyclones to be relatively dry in comparison with synoptic cyclones, yet very windy. These analyses should permit the development of methods to better predict these important cold-season storms over southern middle latitudes, and a fuller assessment of their significance for the larger hydroclimatic system.