Observed characteristics and projected future changes of extreme consecutive dry days events of the growing season in Serbia

Abstract

One of the frequently used drought metrics in scientific research is the consecutive dry days (CDDs) because it effectively indicates short-term droughts important to ecosystems and agriculture. CDDs are expected to increase in many parts of the world in the future. In Serbia, both the frequency and severity of droughts have increased in recent decades, with most droughts being caused by a lack of precipitation during the warmer months of the year and an increase in evapotranspiration due to higher temperatures. In this study, the frequency and duration of extreme CDDs in the growing season in Serbia were analysed for the past (1950–2019) and the future (2020–2100) period. The Threshold Level Method over precipitation data series was used to analyse CDD events, where extreme CDDs are defined as at least 15 consecutive days without precipitation. In contrast to the original definition of the CDD as the maximum number of consecutive days with precipitation less than 1 mm, here we defined the threshold that is more suitable for agriculture because field crops can experience water stress after 15 days of no rainfall or irrigation. An approach for modelling the stochastic process of extreme CDDs based on the Zelenhasić–Todorović (ZT) method was applied in this research. The ZT method was modified by selecting a different distribution function for modelling the durations of the longest CDD events, enabling a more reliable calculation of probabilities of occurrences. According to the results, future droughts in Serbia are likely to be more frequent and severe than those in the past. The duration of the longest CDDs in a growing season will be extended in the future, lasting up to 62 days with a 10-year return period and up to 94 days with a 100-year return period. Results indicate a worsening of drought conditions, especially in the eastern and northern parts of Serbia. The results can help decision-makers adapt agricultural strategies to climate change by providing information on the expected durations of extreme rainless periods in future growing seasons. Although the analysis was performed in Serbia, it can be applied to any other region.