Drought in Croatia in the context of weather types

In Croatia, drought causes the highest economic losses inflicting serious damages, especially in the agricultural and water management sectors. Only in 2003, the drought damage was 90 %. Even though drought can occur in every season, the greatest damage caused by drought occurs in the warm part of the year, particularly in summer, when the absence of precipitation is combined with high air temperatures. For spatial and temporal comparison of drought events in different parts of the world and different periods throughout history in meteorological practice the standardized precipitation index, SPI is the most often used. Accordingly, in this analysis, the SPI index is used for detecting drought events in Croatia in previous decades.

The products of the COST733 action “Harmonization and Applications of Weather Types Classifications for European Regions”, both catalogue and software, were applied to the Croatian area to improve previous knowledge and practice, and to develop a classification that is intended to be the most appropriate to capture precipitation conditions in Croatian regions. For this purpose, Croatia is divided into five regions to acknowledge the orography and climate diversity of the Croatian area which lead to different weather conditions within the same atmospheric circulation. The efficacy of different objective classifications is examined utilizing Croatian meteorological station data.

Selected classifications are compared and their ability to represent drought dynamics in Croatia is evaluated. The goal is to identify classifications that are best suited to capture spatiotemporal drought variability in the Croatian area. For this purpose, the percentage anomalies approach is used for quantifying the relationship between occurrence frequencies of weather types and exceedances/undershootings of specified SPI-thresholds. Further, the analysis aims to identify the main weather patterns responsible for drought events and spatial variations in drought impacts and manifestations among Croatian regions are examined as well. Moreover, temporal variations concerning circulation-drought relationships are also analyzed.