ON THE INTERPRETATION AND CLASSIFICATION OF MESOSCALE CYCLONES FROM SATELLITE INFRARED IMAGERY

Subjective interpretation of cloud imagery is commonly used to identif y mesoscale cyclones in cold air streams (mesocyclones) over the south ern oceans. To determine mesocyclone attributes, and evaluate the clas sification of their cloud vortex signatures, Defense Meteorological Sa tellite Program (DMSP) Infrared (IR) imagery is analysed for selected transition and winter season months of 1988 and 1989. Mesocyclones occ upy a statistically smaller size range compared with synoptic scale (f rontal) vortices, and have maximum frequencies of occurrence in transi tion season months. The mesocyclone classification scheme separates th e 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 le vel associated with vortex types, provide insights into mesocyclone dy namics that are now being evaluated using microwave techniques.