On the ocurrence of Groszwetterlagen in winter related to anomalies in North Atlantic sea temperature

Abstract

In this article, the main results of an investigation concerning the relation between deviating Atlantic sea temperatures and the frequency of occurrence of "Grof wetterlagen" in winter are presented. It appeared that blocking systems over North-west Europe more frequently occur if in the northern part of the North Atlantic sea temperatures are higher than normal and in the southern part lower than normal. A positive sea temperature anomaly in the western part of the Atlantic seems to be a favourite condition for the occurrence of atmospheric circulation systems with a trough over Europe. A tentative interpretation of the obtained results is given. It is concluded that the direct effect of an anomalous heat transfer to the atmosphere, namely an anomalous increase of the vertically averaged air temperature, may account for the results. Furthermore, as an example, the circulation during the last quarter of 1974 related to the sea temperature anomaly pattern is shortly discussed.