Regional characteristics of cloudiness in Serbia during the period 1991–2017

Monthly climate data of days with clear and cloudy skies at 38 stations (1991–2017) daily visual observations total cloud amounts (TCA) available six principal (1992–2017) were used to investigate regional, subregional, temporal characteristics cloudiness in Serbia. Annual, seasonal, monthly means the analysis. Results showed differences due influences from topography, predominant synoptic situations, possible teleconnection North Atlantic Oscillation (NAO). According our criteria, annual number cloudy-sky (~80–120) was higher than that selected clear-sky (~50–90), except for 3 years prevailing anticyclonic circulations. A maximum frequency winter (December), while a minimum summer (August). TCA variability highest an area complex orography. Southeast Serbia characterized by smallest variation based on 7, 14, 21 h as well high during all seasons, western mountainous part much cloudier. From October January, morning afternoon TCA, ranging 70% (January) 78% (December). Statistically significant positive trends found three stations. statistically moderate positive/negative correlation coefficient between cumulative frequencies clear-sky/cloudy-sky NAO respectively. During 18 winters negative index (i.e., frequent westerly warm moist advection), there approximately times more (588) (88).