Changes in the frequency of sharp cold snaps in spring during the XXI century in Ukraine and their impact on agricultural production

Aim. Identification of trends in the frequency of sharp inter-day decreases in the average daily air temperature of varying intensity in spring in the agroclimatic zones of Ukraine and their likely change by the end of the twenty-first century for climate scenarios of representative concentration pathways of greenhouse gas emissions RCP4.5 and RCP8.5. Methods. Solving the set tasks envisaged the application of both conventional scientific and specialized research methods: analytical and synthetic – to analyze the current state of research, statistical – to assess the intensity and significance of changes in the frequency of sharp inter-day air temperature drops of varying intensity, comparative analysis – to identify their specificities in agroclimatic zones of Ukraine, climatic – to characterize extreme temperature conditions, modeling – to assess their changes in the short, medium and long term under the implementation of RCP4.5 and RCP8.5 scenarios. Results. The current state of changes in the extremes of temperature conditions in spring, in particular, sharp inter-day changes in air temperature of varying intensity (severe, very severe, extremely cold snaps) in the agroclimatic zones of Ukraine, is considered. Sharp cold snaps aggravate agricultural production since the decrease in temperature by 4–10 °C or more often leads to light frosts, which may cause partial or complete death of plants. The specificities of their frequency and intensity in 1981–2020 were determined. It was found that in spring, the sharpest cold snaps of 4–6 ºС in Ukraine occur 2–4 times per season; they are most frequent (3–4 times) in the western and eastern Forest-Steppe and Polissia. Very severe cold snaps of 6–10 ºС are observed 2–3 times less – from 6–8 cases in 10 years in the southern Steppe to 13–16 cases in Polissia, in the western and eastern Forest-Steppe. The extremely cold snaps of 10 ºС and more are rare in spring in Ukraine – from 2–3 to 8–9 cases in one hundred years. Conclusions. It was determined that despite a considerable increase in air temperature in Ukraine, Europe, and Arctic latitudes, the earlier beginning of the warm season and vegetation season, the number of spring days with severe, very severe, and extremely severe cold snaps is increasing in almost the entire territory of Ukraine. The north-eastern and eastern regions of the country are most vulnerable due to the registered highest increase in air temperature and frequency of sharp cold snaps. There may be fewer sharp cold snaps in the short- and long-term perspective in Ukraine as compared to the current climatic period. Still, the frequency of extremely cold snaps (over 10 ºС a day) will increase by the end of the century, especially in Polissia, and the western and central Forest-Steppe. These changes may result in premature termination of the vegetation period, damage to primordia and fruits, impairments to normal plant development, and a significant effect on crop productivity.