Long-term changes in fire weather conditions in Ukraine

This study investigates spatiotemporal changes in fire-dangerous weather conditions across Ukraineduring the period 1960–2023. Daily temperature and relative humidity data from ERA5 reanalysis wereused to calculate Angstrom index, which reflect the level of potential fire danger based on meteorologicalconditions. An assessment of the frequency of fire danger classes based on the threshold values of the Angstrom index revealedsignificant positive trends in the frequency of days with extreme and high fire hazard in most of Ukraine duringthe warm season (April–October), with the greatest increase observed in the southern and southwesternregions. The results demonstrate the potential of using the Angstrom index both for the operational assessment of fireweather danger and for the development of a comprehensive system for assessing and forecasting fire riskin various landscape zones of Ukraine.