ARCTIC SYNOPTIC ACTIVITY IN WINTER

Abstract

The wintertime distribution, structure and motion of cyclones and anticyclones in the Arctic are analyzed through the use of 15 winter months of data. Histories of the most important types of pressure systems are described, and note is made of the interaction between the Arctic and middle latitudes. The effect of the receipt of weather reports from the central Arctic on previous concepts of the circulation is discussed. This study shows that the Arctic is a region of great synoptic activity with cyclones outnumbering anticyclones about 2 to 1. The central Arctic Basin is a region of cyclonic frequency equivalent to any place in the Northern Hemisphere outside of the semipermanent centers of action. In the mean, cyclones are warm in the troposphere because most of them enter the Arctic from over the warm waters of the Atlantic Ocean. Cyclones which originate in the Arctic are cold-core. Anticyclones, in the mean, are colder than cyclones. However, their centers are usually capped by slightly warmer air, from the oceanic ridges, than is present over their peripheries.