Long‐term variability of the cloud amount and cloud genera and their relationship with circulation (Kraków, Poland)

The article demonstrates the impact of atmospheric circulation on the long‐term variability of cloudiness (amount and certain cloud genera) in Kraków based on midday observations of the amount and genera of clouds in the period from 1 January 1906 to 31 December 2015. There was found statistically significant (although rather moderate) correlation between circulation indices and the frequency of cloud cover consisting of a single cloud genus or a group of clouds. The 11‐year moving averages of frequency of occurrence of one‐genus cloud cover show periods of alternating increasing/decreasing trends, some of which are multi‐decadal. Decreasing trends, lasting till now, are shown for Cirrostratus, Nimbostratus and Stratus beginning from the 1920s to 1930s and for Altostratus from the 1970s. The Cirrus, Stratocumulus and Cumulus trends are generally increasing from the 1920s, 1950s and 1950s, respectively.