INSTITUTE OF GEOGRAPHY AND SPATIAL ORGANIZATION POLISH ACADEMY OF SCIENCES www.igipz.pan.pl www.geographiapolonica.pl Geographia Polonica 2017, Volume 90, Issue 1, pp. 21-38 https://doi.org/10.7163/GPol.0076 CLOUD COVER OVER SPITSBERGEN AND ITS RELATION TO ATMOSPHERIC CIRCULATION (1983-2015) Ewa Łupikasza • Oskar Lipiński Department of Climatology, Faculty of Earth Sciences University of Silesia in Katowice Będzińska 60, 41-200 Sosnowiec: Poland e-mails: ewa.lupikasza@us.edu.pl • oskar.lipinski18@gmail.com Abstract This paper discusses the cloud cover and its relation to atmospheric circulation over Spitsbergen during 1983-2015. It focuses on monthly and seasonal cloud covers and on the frequency of days with specific cloud cover (cloud- less, clear, cloudy and completely overcast sky) and their relation to various circulation types. In the research period the cloud cover characteristics were differentiated over the island on both monthly and seasonal scales, and they strongly depended on the direction of air advection. The highest mean daily cloud cover was reported for circulation types with air advection from the south (S+SWc and S+SWa). The greatest variation in the cloud cover distribution was observed during the polar night (at Svalbard Lufthavn and Ny-Ålesund) or in the au- tumn (Hornsund). The long-term variability in the cloud cover significantly depends on the frequency of N+NEa type (negative correlation) and on S+SWc and W+NWc and Cc+Bc types (positive correlation), particularly in spring. Key words cloud cover • atmospheric circulation • Spitsbergen • the Arctic Introduction An increase in air temperature, shrinking sea ice extent or a variable pattern of baric field can significantly influence the fraction of the sky obscured by clouds in the Arctic. Unlike majority of climate elements, the cloud cover is measured by visual assessment of the sky fraction covered by clouds. The type and oc- currence of cloud cover may indicate a current state of the atmosphere, or spell its future modification. Clouds may undergo various modifications, thus significantly influencing the radiation balance of the Earth surface and atmosphere and finally impacting air tem- perature (IPCC 2007; Przybylak 2007; Vavrus et al. 2011; Matuszko & Soroka 2013; Bednorz et al. 2016). Cloud cover modifies the amount of the solar radiation reaching the Earth sur- face and thus significantly influences human