engleski

Changes in Precipitation Variability in Osijek

Osijek is situated in Eastern Croatia, region with lowest amount of precipitation in Croatia. Therefore, analyzing precipitation variability changes is important for different types of human activities, i.e. agriculture and water management. This paper analyses variability of precipitation in Osijek in three periods of thirty years, starting from the year 1901 till 1990. Precipitation variability has been calculated using different methods of mean arithmetic deviation. Besides that, the changes in precipitation amount were determined in order to establish regularity between changes in precipitation amount and variability. Sixty-year period has been determined from the year 1931 till 1990, because none of the thirty-year period was representative. A primary minimum of precipitation is at the end of winter and at the beginning of spring (March), while secondary minimum is in autumn (October). Primary maximum is at spring and summer (June), and secondary maximum is in autumn (October). Seasonal averages show that precipitation maximum is in summer and minimum in winter. Analyses of precipitation variability reveal that annual variability course is characterized with two maximums and two minimums of variability. Primary minimum of variability is in spring and summer (minimum in June, rarely in July or August) and secondary is in winter (minimum in November or December). Primary maximum of variability is in autumn (maximum in October, rarely in September) and secondary maximum is in spring (maximum in February). It is important to notice that May is enhanced in the period of primary minimum in spring and summer, with a slightly higher relative average variability. It has been determined that relationship between change of precipitation and variability is not simple. Correlation analysis of ten-year precipitations averages and variability shows that there is a moderate negative connection in August and October. Correlation analysis of thirty-year averages shows that there is a moderate negative connection in June and September. Statistically, close negative connection is in October and in summer, but no strong negative connection is determined. Course of precipitation amount and variability in observed period shows close positive connection. Increase of precipitation amount does not have to cause variability decrease. It can be assumed that larger increase or decrease of precipitation amount can cause adequate decrease or increase of variability, but the research results did not point under what circumstances that happens. Influence of possible factors of that connection could not be excluded, especially the influence of processes that cause precipitation genesis in Osijek. Nevertheless, during some months a decrease of precipitation amount and variability increase (and vice-versa), can be connected, like it is a case in October.

precipitation; precipitation variability; climate changes; Osijek

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