A Joint Perspective on North American and Euro-Atlantic Weather Regimes

Weather regimes are recurrent and quasi-stationary large-scale atmospheric circulation patterns, typically linking to surface weather. Two commonly used sets of weather regimes are wintertime North American and Euro-Atlantic regimes. Notwithstanding recent evidence pointing to a connection between winter weather in North America and Europe, there is little knowledge on the possible relation between North American and Euro-Atlantic regimes. Here, we find that specific pairs of North American and Euro-Atlantic regimes show a close visual and statistical correspondence. Moreover, the joint analysis of the two sets of regimes can provide medium-range statistical predictability for anomalies in their occurrence frequencies. Conditioning on North American weather regimes also results in anomalies in both the large-scale circulation during specific Euro-Atlantic regimes, and the associated European surface weather. We conclude that there is a benefit in conducting joint analyses of North American and European weather regimes, as opposed to considering the two in isolation. Wintertime weather in Europe is closely related to large-scale atmospheric patterns occurring over scales of thousands of kilometers. These patterns, termed weather regimes, are relatively persistent in time, and occur repeatedly. Such weather regimes have been used for many applications, including predicting the weather several weeks in advance. Weather regimes conceptually similar to those identified for Europe have also been determined for North America. In this study, we look at whether and how North American and European weather regimes are related. We show that the two sets of weather regimes have a statistical link, and that accounting for North American regimes can help to gain a more detailed understanding of how European regimes relate to weather in Europe. Specific pairs of North American and Euro-Atlantic weather regimes show a close relationA joint analysis of the two sets of regimes can provide statistical predictability for anomalies in their occurrence frequenciesNorth American regimes have a clear footprint on the European surface weather associated with Euro-Atlantic regimes

Automated summary

The North American and Euro-Atlantic weather regimes show a close statistical correspondence, and a joint analysis can provide statistical predictability for anomalies in their occurrence frequencies. North American regimes have a clear impact on the European surface weather associated with Euro-Atlantic regimes.