Climatology and Trends of Sub‐Daily Precipitation Extremes in Croatia

ABSTRACT The increasing frequency of flash floods in recent decades has been linked to climate change, particularly to the rising intensity and frequency of short‐duration rainfall events. This study analyses the climatology and trends of sub‐daily precipitation extremes in Croatia, a complex area situated in a transitional zone between the European mainland, the Alpine region and the Mediterranean. The analysis, performed on annual and seasonal scales, is based on 1‐, 3‐, and 6‐hourly data from a dense network of ombrographic stations covering the 1981–2020 period. Trends were assessed using a linear regression model within a Bayesian framework and the associated probability of direction. The results show that the highest number of wet hours occurs in spring and autumn across inland Croatia, while in the mountainous and Adriatic regions, wet hours peak in late autumn and winter. The cold seasons generally exhibit the longest wet spell durations. The most intense and frequent sub‐daily precipitation extremes were recorded in the northern and southern Adriatic regions and in the highlands, with maxima in early autumn, typical of the Mediterranean climate. In the continental part, however, significant contributions of sub‐daily extremes to daily rainfall were found during summer months. The timing of peak intensity and frequency coincides within each region, suggesting that both are driven by similar convective and thunderstorm processes. Hourly rainfall maxima typically occur around midnight, shifting to the afternoon in inland areas during the warm season, while along the Adriatic coast and islands they prevail at night or in the early morning. A general tendency toward more frequent and intense rainfall was detected, with increasing intermittency over the mainland and prolonged wet spells along the Adriatic. These findings provide a valuable basis for assessing flash flood risk and for improving climate modelling and adaptation strategies in the context of a changing climate.