Atmospheric variability occurs over a large range of spatial and temporal scales and impacts on surface weather and climate. The range of phenomena includes transient synoptic features, polar vortices, planetary waves, jet streams and distinct modes of other low-frequency variability, such as the high-to-mid latitude Southern Annular Mode, the Arctic Oscillation (AO) and the related Northern Annular Mode (NAM) and the North Atlantic Oscillation (NAO), as well as the Pacific-North-American (PNA) teleconnection pattern. These patterns are associated with the atmosphere-ocean modes in the tropics (e.g. El Nino-Southern Oscillation) and polar regions (e.g. changes in sea ice and snow cover).

There have been significant advances in diagnosing and modelling many of these circulation phenomena. However, many questions remain regarding their interactions and their long-range influences. As an example, a number of extreme weather events in the Northern Hemisphere mid-latitudes during the past decade has focused attention on changes in the mid-latitude atmospheric circulation, and there is an ongoing debate on whether these changes are related, and also whether they may be influenced by Arctic climate change.

This session covers observational and modeling studies of a range of scales of atmospheric variability, and addresses questions of linkages between regional climate change, large scale circulation variability and their relationship to high impact weather.