Keywords: thermal regime, climate change, representative concentration pathways, climate characteristic projections, date of persistent air temperature transition

The article presents the results of the study of thermal periods in Ukraine, namely its second part, which concerns the duration and dates of the beginning and end of the growing season, which is determined by the persistent transition of the average daily air temperature through the value of 5 °C. Climatic characteristics of the growing season determine the beginning and end of agricultural work, as well as a number of other activities that are carried out, for example, in forestry and other farms. The methods for determining climatic characteristics in this study were similar to those used in the first part, where changes in the warm period were analyzed (Krakowska et al., 2023, http://doi.org/10.15407/Meteorology2023.04.035). The values of the climatic characteristics of the growing season for the climatological norm 1961-1990 and the base period 1991-2010 were calculated using data from the European E-OBS database, and projections of changes relative to the base and values in the future three periods (2021-2040, 2041-2060 and 2081-2100) were calculated using daily data from 34 regional climate models (RCMs) of the international initiative for Europe Euro CORDEX under the RCP 4.5 and RCP 8.5 scenarios. The calculations used the eca_gsl function of the CDO (Climate Data Operator) software package to determine the dates of the steady temperature transition through 5°С. To correct the differences in the masks in E-OBS and the RCM ensemble due to the difference in the number of grid points mainly on the coastal line, the geographic information system QGIS 3.28 were used, with the help of which mapping was also carried out for visualization and analysis of the results with subsequent presentation in the form of maps in an electronic atlas using JavaScript-Leaflet library. The growing season length will increase throughout the country until the end of the century. These changes are expected to be more uniform than changes in the duration of the warm period. The duration of the growing season, which at the beginning of the 21st century was characteristic only for the southern coast of the Black Sea and the Crimean Peninsula, at the end of the century, under the implementation of the high-concentration scenario RCP 8.5, may also be characteristic of the far northeast of the country and the Ukrainian Carpathians. It is obvious that this will significantly change and will require rapid adaptation of ecosystems and changes in forestry and agro-industrial practices. The presented results can be used in the development of sectoral, national, regional and municipal strategies for adaptation to climate change.

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