Atmospheric conditions governing anomalies of the summer and winter cloudiness in Spitsbergen

Abstract

The study is based on data concerning cloudiness for the years 1981–2010 from Svalbard Lufthavn. Atmospheric circulation was characterized using a catalogue of circulation types developed by Niedźwiedź (2013) and average daily values of atmospheric pressure. Intensive cyclogenesis taking place over the north Atlantic expressed by lower-than-normal sea level pressure (SLP), particularly over the Fram Strait and over the east coast of Greenland, enhances the meridional air transport from the southern sector which conveys positive anomalies of cloudiness, namely a very cloudy weather. Negative anomalies of cloudiness over Svalbard Lufthavn occur in the winter when the north Atlantic cyclone path is shifted to the south and goes along the northern Norwegian shore towards the south Barents Sea. In summer, the influence of pressure patterns on cloudiness is weaker than in winter and different circulation patterns induce negative extremes of cloudiness. In the warm season, sunny weather occurs when a distinct anticyclone spreads over the Svalbard Archipelago and to its west, over the Fram Strait and the northern outskirts of the Greenland Sea. Extremely cloudy weather occurs in summer when a weak anticyclone spreads over the Barents Sea, the Novaya Zemlya archipelago and the Kara Sea, while slightly lower-than-normal pressure is observed over Greenland. Such a pressure pattern enhances southerly and south-westerly flow of air masses, bringing humid air. The results obtained in this study demonstrate that cloudiness over Spitsbergen is strongly controlled by the air circulation arising from pressure patterns.