engleski

Trend and variability in heavy precipitation in Croatia

This analysis deals with two types of precipitation time-series. Initiatory annual and seasonal amounts are discussed, followed by trend analysis in six indices of precipitation extremes indicating intensity and frequency of extreme rainfall events. Indices have been proposed by World Meteorological Organization and calculated after daily precipitation amounts. The data sets cover the period 1901-2008 at five meteorological stations in Croatia covering different climate regions: continental, mountainous and maritime. Trends are estimated by a simple least squares fit of the linear model, and tested for statistical significance by a non-parametric Mann-Kendall test. Sneyers progressive analysis of the time series characterized by the significant trend is performed in order to determine the beginning of the trend. Short-term fluctuations are taken out of the data series by the weighted 11-year binomial moving average filter. Variability is performed by time series analysis of coefficients of variation in consecutive 30- and 50-year periods depending on the parameter. The extreme quantiles for annual one-day and five–day precipitation maxima series have been estimated by Generalized Extreme Value (GEV) distribution and discussed in relation to the original time-series. Since the beginning of the 20th century annual precipitation amounts show a downward trend in all parts of Croatia, thus joining the trend of drying across the Mediterranean. Precipitation amounts have large interannual variability, both on annual and seasonal scales. It shows a decrease in NW Croatia, mountainous region, northern littoral and in the eastern lowland by the end of the 20th century. Dalmatian islands experienced an increase of variability in a period from the middle of the 20th century. In the area of drying such as Croatia there is no signal of major secular changes in extremes related to the high amounts of precipitation and frequency of heavy rainfall days over the larger part of Croatia.

trend analysis; precipitation variability; indices of precipitation extremes; seasonal precipitation; annual precipitation; GEV distribution; Croatia

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