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

Abstract

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.

Trends in sunshine duration in Poland (1971–2018)

“…Based on the conducted analysis, it was found for all months that the correlation between atmospheric circulation type and area‐average monthly SD is stronger for the type of pressure system than for the direction of air mass advection (Figure 7). A similar relationship was found for other climate elements in Poland, for example, for cloud cover and precipitation (Twardosz and Niedźwiedź, 2001; Matuszko and Węglarczyk, 2018). The area‐average monthly SD in Poland show a strong statistically significant relationship with the type of pressure system, that is, positive in anticyclonic situations and negative in cyclonic situations (Figure 7).…”

“…After 1990, there was another increase in the cyclonicity index and a slight increase in cloud cover over the entire decade, followed by a several-year decrease and another increase by 2010. The beginning of the second decade of the 21st century indicates a further decline in the cyclonicity index and a weakening of the zonal circulation with the western component, while there was an increase in the meridional circulation with the southern circulation, reaching a maximum in 2014 (Matuszko and Węglarczyk, 2018).…”

“…The high variability of area‐average monthly SD from month to month indicates the dynamics of the circulation conditions in Poland affecting cloud cover and the content of aerosols in the atmosphere. The concentration of summer months (July, August) belonging to the lowest quantile class in the years 1977–1981 (and, in addition, in June 1980 and 1981) makes it possible to assume that the main reason for low SD in this period may be ascribed to cloud cover (Matuszko and Węglarczyk, 2018). From the last decade of the 20th century to the end of the period under study, there was a predominance of months in the highest quantile (Figure 4), which does not mean that there were no months in the lowest class of SD .…”

“…With the sky overcast, layered clouds of primarily Stratus , Altostratus and Nimbostratus type are impervious to solar radiation (Matuszko, 2012b). In Poland and other regions of the world, especially in the last 40 years, an increase in the incidence of vertical clouds, a decrease in the incidence of layered clouds, and more frequent occurrence of high‐level clouds has been observed (Sun and Groisman, 2000; Wibig, 2008; Eastman and Warren, 2013; Matuszko and Węglarczyk, 2018).…”

Spatio‐temporal variations of cloud fraction based on circulation types in the Iberian Peninsula

“…However, there is only one known study relating cloud distribution to synoptic circulation (Sanchez‐Lorenzo et al ., ). On an international level, more studies can be found on atmospheric patterns affecting cloud cover (Rmillard and Tselioudis, ; de Szoeke et al ., ; Matuszkoa and Weglarczyk, ; Mechem et al ., ). Therefore, a comprehensive study of cloudiness using data collected from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard the Terra and Aqua satellites has been carried out relating it to the classification of local‐regional synoptic patterns.…”