Projections of continentality and cold season indices in Ukraine based on the ensembles of Euro-CORDEX RCMs

Abstract

<p>The updated climate projections with fine spatial resolution of 0.1⁰ allow to evaluate more precisely regional features as climate change impacts unevenly on various geographical regions. The analysis performed for understanding the quantitative changes of climate characteristics for indicating climate extremity in cold season and daily (DTR) and annual (ATR) temperature ranges, and Ivanov index of thermal continentality (IITC) for Ukraine that can be used as the additional information for economic sectors. This research is based on the observational E-Obs v20.0e dataset and ensembles of 34 RCMs for RCP4.5 and RCP8.5 using the base periods of 1961-1990 and 1991-2010, and future ones – near-term (2021-2040), mid-term (2041-2060), and far-term (2081-2100). All characteristics were averaged for each 20-year period and bias-adjusted with applying the delta-method for avoiding and smoothing unnecessary fluctuations. It has been found that the general tendency for ATR will be decreasing with value 1-2°C and shifting from the west to the east for RCP4.5 and RCP8.5. It could be explained by the general trend of temperature increase and possible shrinking of temperature contrasts between the warmest and the coldest months. In comparison to ATR, DTR has low variations and not such apparent changes. They were detected in some regions with values up to 1°C. According to the results, IITC slightly variates over the region during the studied period, but the continentality increases in south-eastern regions of Ukraine based on RCP8.5 scenario in 2081-2100. In addition to, extreme temperature changes such as numbers of frost (FD) and ice days (ID) have been analyzed. They refer to cold season and are indicators of the harshness of the climate. Selected periods of climate projections allow to analyze the dynamics of climate change. Air temperature rise will provoke a significant decrease in the FD determined by daily minimum temperature (mostly in nights) during cold season up to 2100 for both scenarios. According to RCP4.5, the FD could decrease by the end of the century from 22 in the south to 34 nights or more in northern part of Ukraine. For the RCP8.5 scenario, FD possibly shorten by minimum 40 days on the coasts of Black and Azov Seas to 64 days or more in the north. To sum up, the FD will variate from 30 to 60 a year in Ukraine, except for the Carpathians and the east-northeast. For ID determined by daily maximum temperatures, maximum reduction of over 20 days are projected in the Carpathians and north-eastern part while they are from 15 to 20 days resulted in average 30 ice days per year for the most territory of the country based on RCP4.5. Substantial decrease in ID comparable with the recent one is projected in RCP8.5 till the end of the 21st century. It will result in less than 30 ID at most in northeast part for the country, only 10 days more in the coldest part of the Carpathians and extremely low number of ice days for the warmest part of the country namely Transcarpathia, the south and south-west.</p>