The East Atlantic Oscillation: Mechanism and Impact on the European Climate in Winter

Abstract

The second principal component of the atmospheric pressure field resolution in the Atlantic-European region called the East Atlantic Oscillation (EAO) is considered. The EAO spatial structure in the field of the isobaric surface geo-potential 500 hPa is represented by a dipole with the centers over the North Atlantic and the Central Europe. Change of the atmospheric pressure in the centers of the EAO action (change of the EAO phase) is connected with change of the general circulation type in the re-gion. During the EAO positive phase the zonal type of circulation dominates, during the negative one – the meridian type is predominant. This phenomenon is reflected in change of the extra-tropical cyclones’ storm-tracks and impacts formation of the anomalies of the surface air temperature and precipitation fields in Europe in winter. The mechanism of the EAO influence upon the atmospheric fields of the Atlantic-European region is realized through change of location and intensity of the mid-troposphere jet over the North Atlantic. During the EAO positive phase the jet stream shifts southward, and during the negative one – north-ward.