Recent changes in first and last frost dates and frost-free period in Serbia

Abstract

ABSTRACTThe study analyzes regional differences in the variability of time series of minimum temperatures during the spring and autumn, spatio-temporal variability of the last spring frost date and the first autumn frost date, as well as the length of the frost-free periods, in 15 stations in Serbia for the period 1961–2010. The analysis of trend in dates of frost occurrence over the study period showed that the last spring frost occurred earlier between 0.48 and 2.67 d decade−1, while changes in the first autumn frost occurrence were neither uniform nor statistically significant. Statistically significant earlier occurrence in the last spring frost at majority of stations starts in the mid-1980s, while significant later onset of the first autumn frost occurs in the second half of the 1990s The trend of the frost-free period displayed several distinct periods: (a) becomes shorter in the 1960s, (b) there is no trend in the1970s and (c) extends from the 1980s which is caused by early ending of the spring frost. The S-mode of Principal Component Analysis was applied in order to explore regional aspects of the minimum temperature variability during spring and autumn in Serbia. The influence of atmospheric circulation on observed temperature changes was analyzed using the teleconnection indices. The highest correlation was found for the minimum temperatures and the East Atlantic Oscillation in spring and autumn and for the East Atlantic/Western Russian Oscillation in autumn.