Cloud Cover Changes Driven By Atmospheric Circulation In Europe During The Last Decades

Due to its complex role within the radiation budget of the Earth, cloud cover plays an important role in climate variability at local, regional or continental scale. Consequently, there is a need for better understanding the causes and feedbacks of changes in cloud cover. We aim at investigating the response of cloud cover to changes in atmospheric circulation for 1981-2014. This is done based on the application of automated weather type classification from COST733 synoptic classifications software, which helps in identifying a variety of atmospheric circulation types for selected domains. Two major spatial changes in cloud cover over Europe are identified, in connection with atmospheric circulation, associated with the latitudinal shift towards the north of the westerly circulation. The first one is related to a decrease of the cloud cover over the inner continent and especially in the East of Europe in connection with an increase of circulation types associated with high pressures centers development over the central and northern part of the continent. The second one, which is weaker in intensity, indicates an increase of cloud cover in the south-western part of Europe as a result of a decrease in circulation types induced by the development of the Azores High and its northeastward ridges. The changes in cloud cover distribution and also in radiation fluxes, imposed by these shifts in atmospheric circulation over the continent, are higher in the Eastern and Central Europe.