Satellite climatological aspects of the ' polar low' and ' instant occlusion' ( Pacific, Atlantic).

Middle resolution DMSP (Defense Meteorological Satellite Program) visible and infrared imagery are analyzed in conjunction with surface and upper-air synoptic observations for two years' (1977, 1978-79) mid-season months (January, April, July, October) to derive synoptic climatological information on the 'polar low' and 'instant occlusion' phenomena. Polar-air vortices occur most frequently over the oceans in winter. Regional differences in the dominance of cloud signature sub-types confirm variations in the dynamics involved in polar-air cyclogenesis, as noted by previous workers. The 'common cloud' appears to occur more frequently in the North Pacific, while the spiraliform vortex predominates in the North Atlantic.-Author