POLAR LOWS AND ARCTIC INSTABILITY LOWS IN THE BEAR ISLAND REGION

The study of the "polar low episode" over the northern parts of the Norwegian Sea and the Barents Sea from 12 December 1982 to 16 December 1982 is continued. The role of baroclinic instability in the initial formation of a polar low near the ice edge is considered, including a discussion based on a diagnostic IPV analysis. During the polar low episode, circulations develop on different horizontal scales including true mesoscale phenomena. The mesoscale circulations have the character of symmetric vortices of a much smaller horizontal scale, approximately 100 km, than normally associated with polar lows. Although, during their initial formation, these circulations may be modulated by baroclinic instability associated with a shallow arctic frontal zone, they are predominantly convectively driven. The term "arctic instability lows" is suggested for these disturbances in order to distinguish them from the more "normal" polar lows. The polar low formations take place within a large synoptic scale cold dome. The importance of this cold dome as well of cold domes in general for polar low formations is briefly discussed.