Evaluation of the Spatio-temporal Variation of Extreme Cold Events in Southeastern Europe Using an Intensity-duration Model and Excess Cold Factor Severity Index

Recent studies have revealed a rise in extreme heat events worldwide, while extreme cold has shown a decline. It is highly likely that human-induced climate forcing will double the risk of severe heat waves by the end of the century. Although extreme heat is expected to have greater socioeconomic impacts than cold extremes, the latter contributes to a wide range of adverse effects on the environment, various economic sectors and human health. People can somewhat adapt to extreme temperatures when they experience repeated heat and cold waves, but these extreme events can have more severe health consequences when they occur earlier in the respective season or last unusually long. A few studies have re-cently analyzed extreme heat events on a European scale using the excess heat factor (EHF) that accounts for short-term acclimatization. This approach is also analogously ap-plicable to extreme cold events by employing the excess cold factor (ECF). The present re-search aims to evaluate the spatiotemporal variations of extreme cold events in South-eastern Europe through the intensity-duration model developed for quantitative assessment of cold weather in Bulgaria. We demonstrate the suitability of indicators based on minimum temperature thresholds to evaluate the severity of extreme cold events in the period 1961–2020 both at individual stations and Köppen’s climate zones using daily temperature data from 70 selected meteorological stations. The ability of the used intensity-duration model to estimate the severity of extreme cold events has been compared with the ECF severity index on a yearly basis.