The relationship between flash drought and dry-hot winds in Ukraine

The territory of Ukraine is highly vulnerable to dry phenomena due to its temperate continental location, extensive agricultural lands, and increasing climate variability. Of particular concern are rapidly developing droughts or flash droughts and intense dry-hot winds, both capable of causing severe crop damage.

The occurrence and evolution of flash droughts during the warm season (April–October) of 1980–2024 were analysed using the Standardized Evapotranspiration Deficit Index (SEDI) based on actual and potential evaporation data from the GLEAM project. Flash droughts were identified using SEDI at the 4-week time scale, while daily-scale SEDI values were applied for analysis with dry-hot wind events. Dry-hot winds (known in Ukraine as “sukhovey”) were identified from observation records at 34 stations using threshold criteria of air temperature, relative humidity, and wind speed adopted by the National Hydrometeorological Service of Ukraine.

The highest number of flash drought episodes (up to 30–35 events) was recorded in western and northern Ukraine. Positive trends in drought occurrence prevailed across most regions, especially in the southwest, centre, and north, whereas negative trends were found in the west and parts of eastern Ukraine. Flash droughts in western regions were generally short-lived (2–3 weeks), while the longest events (6–8 weeks) occurred in southwestern and central Ukraine. Most flash drought episodes were highly intense, frequently reaching extreme drought conditions (SEDI < −2.0), although their intensity showed a general decreasing trend during the study period.

Five major flash drought episodes affecting at least 20% of Ukraine were identified during 1980–2024, lasting from 3 to 7 weeks. In most cases, dry-hot winds developed after drought onset, with their frequency increasing toward the middle of drought episode. Under dry conditions, dry-hot winds were associated with increased SEDI values, indicating temporary weakening of drought intensity. Thus, dry-hot winds do not initiate flash droughts but may influence their spatial development through changes in intensity.