Trends and possible causes of cloudiness variability in Montenegro in the period 1961-2017

Abstract

Cloudiness is an important climate parameter, and it is closely related to insolation, temperature, and precipitation. Total cloud cover (TCC) data along with the number of cloudless (CL) and overcast (OC) days from 18 stations in Montenegro during the period 1961-2017 were used to determine the seasonal trends and possible causes of cloudiness variability. The Mann-Kendall test and Sen’s slope were used for trend detection. We found statistically significant (p < 0.05 and p < 0.10) decreasing (increasing) trends in TCC (the number of CL days) in winter, spring and summer. The exception was in autumn, when an increase (decrease) in the TCC (CL days) was shown, but in most cases, these changes were insignificant. The number of OC days declined in coastal and central regions, while a positive trend was found in the northern region for all seasons. The increase in the number of CL days during the summer and winter was more pronounced compared to the decreasing trend in the number of OC days. Pearson’s correlation (r) was used to access the relationship between cloudiness and principal modes of atmospheric variability such as North Atlantic Oscillation (NAO), Summer North Atlantic Oscillation (SNAO), Arctic Oscillation (AO), East Atlantic Oscillation (EA), East Atlantic-West Russian Oscillation (EAWR), Scandinavian Pattern (SCAND), Polar-Eurasian Oscillation (POLEUR), North Sea-Caspian Pattern (NCP), and South Oscillation (SOI) as well as regional patterns of climate variability—the Mediterranean Oscillation (MOI) and Western Mediterranean Oscillation (WeMO). A significant consistency (r > 0.60, p < 0.05) was found between time series of certain atmospheric circulation patterns and cloud parameters (NAO, AO, EAWR, SCAND, NCP, and MOI-1), especially in the colder half of the year.