Semenova I. Synoptic and climatic conditions of forming the drought phenomena in Ukraine

Dissertation is devoted to the scientific problem of determination a drought as a complex phenomenon which is formed under the certain temperature and moisture conditions and under influencing of some circulation atmospheric processes to improve forecasting methods of crop yields. Five indices of atmospheric drought were chosen as a complex parameter: the hydrothermal coefficient by Selyaninov, the index of atmospheric aridity by Ped', the Palmer drought severity index, the Standardized precipitation index, the Standardized precipitation-evapotranspiration index. Joint using of them allowed creating the catalog of seasonal droughts in Ukraine during the vegetation period of 1995-2012. Spatiotemporal distribution of drought in the vegetation periods of 2020-2050 was obtained using the global climate modelling data sets within the representative concentration pathways. Regional features of atmospheric processes for periods of drought are identified by assessing of the atmospheric blocking using the index of Lejenas-Okland and the European continental blocking index (ECBI), which introduced in research. Evolution of blocking processes investigated using analysis of energy transformation in the atmosphere during the blocking. For forecasting the yields of winter wheat and spring barley is implemented a method, which is based on coupled of the drought impact and blocking processes in the atmosphere. Constructed regression equations allow to make a forecast in most regions of Ukraine in June before 1.5-2 months to the harvesting.