Vol. 60., No. 1, 2025
Abstract
This study investigates spatiotemporal changes in fire-dangerous weather conditions across Ukraine during the period 1960–2023. Daily temperature and relative humidity data from ERA5 reanalysis were used to calculate Ångström index, which reflect the level of potential fire danger based on meteorological conditions. Trend analysis revealed a consistent decrease in Ångström index values across regions of the country and in all seasons, indicating an overall increase in fire danger during the study period. An assessment of the frequency of fire danger classes based on the threshold values of the Ångström index revealed significant positive trends in the frequency of days with extreme and high fire hazard in most of Ukraine during the warm season (April–October), with the greatest increase observed in the southern and southwestern regions. The average number of extreme fire danger days has increased by more than 1.5 times since 1960, reaching 51 days in the recent decade. The analysis of the relationship between burned areas and number of days in different fire danger classes in warm period of the year revealed clear regional differentiation depending on index thresholds. In forested regions, the largest burned areas were associated with extreme and high fire danger classes. By contrast, in steppe and forest-steppe zones, the greatest burned areas occurred under less severe weather conditions corresponding to the moderate fire danger class. The results of the study demonstrate the potential of using the Ångström index both for the operational assessment of fire weather danger and for the development of a comprehensive system for assessing and forecasting fire risk in various landscape zones of Ukraine.