On the interpretation and classification of mesoscale cyclones from satellite infrared imagery

Subjective interpretation of cloud imagery is commonly used to identify mesoscale cyclones in cold air streams (mesocyclones) over the southern oceans. To determine mesocyclone attributes, and evaluate the classification of their cloud vortex signatures, Defense Meteorological Satellite Program (DMSP) Infrared (IR) imagery is analysed for selected transition and winter season months of 1988 and 1989. Mesocyclones occupy a statistically smaller size range compared with synoptic scale (frontal) vortices, and have maximum frequencies of occurrence in transition season months. The mesocyclone classification scheme separates the different signature types most reliably in winter, which is also the season when they are most frequently represented on hemispheric-scale synoptic chart analyses. Characteristic patterns of cloud form and level associated with vortex types, provide insights into mesocyclone dynamics that are now being evaluated using microwave techniques.