Climatological “models”; of cold air mesocyclones derived from SSM/I data

Abstract

A major limitation of satellite infrared data used to detect mesocyclones occurring in cold airstreams over datavoid oceanic regions is the inability to document the basic structure of these systems. In this research we use the integrated water vapor (IWV), integrated cloud liquid water (ICLW), precipitation, and surface wind speed information retrieved from the SSM/I (Special Sensor Microwave/Imager) of the DMSP (Defense Meteorological Satellite Program) platform to develop climatological (statistical mean) “models”; of mesocyclone structure and evolution for the southern oceans. Composite analysis of sea level pressures and 500 hPa heights shows that mesocyclones frequently develop in the region between strong synoptic‐scale pressure and height anomalies, and over positive differences in sea‐air temperature. Climatological “models”; (statistical means, standard deviations) of marine atmospheric variables retrieved from the SSM/I indicate that mesocyclones have associated strong horizontal wind shear: highest wind speeds occur in the northwest quadrant and lowest wind speeds in the southeast quadrant of these storms. The composite IWV ranges from low to moderate values (5–15 kg m‐2) that increase from south to north within mesocyclones. Solid precipitation seems to dominate over rain in most of these systems. An estimate of the surface sensible heat flux for one mesocyclone outbreak suggests that surface energy plays an important role in mesoscale cyclogenesis over the oceans.