engleski

Trends of precipitation amount, frequency and intensity in the Croatian lowland

Precipitation trends at the meteorological station in Osijek, situated in the continental Croatian lowland, were examined on seasonal and annual basis for the period 1899-2003. Annual, spring and autumn precipitation have decreasing trend (-80.8mm/100yr, -70.1mm/100yr, -23.8mm/100yr respectively). Summer precipitation slightly increases 11.3 mm per 100 years, while wintertime precipitation has almost no trend (0.2 mm/100yr). The decreasing trend of spring precipitation is significant according to the Kendall's nonparametric test, whereas other trends have no statistical significance. Furthermore, the spring precipitation regime was examined in terms of the trend of daily precipitation amounts and frequency of the days with precipitation for various categories of precipitation defined by five percentile class intervals. Precipitation thresholds (e.g. percentiles) were calculated by fitting the gamma distribution to the daily precipitation amounts of the 1961-90 reference period. For each class interval the contribution to the total trend attributed to trends in precipitation frequency (number of days) and intensity (daily amount) was determined. For the frequency component, contribution (cf) was calculated from average daily precipitation and the trend of number of days with precipitation (td). The contribution of the intensity component (ci) was calculated as a difference of the precipitation trend t for the particular class interval and cf. The total spring precipitation trend is mostly due to the decreasing trend of precipitation within the upper 5% of daily precipitation amounts (72% of the total trend) which is mainly caused by the decrease of the number of precipitation events (e.g. frequency component).

precipitation amount; intensity; trend

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