Tropical nights (1976–2019) as an indicator of climate change in Ukraine

Abstract

Abstract The article presents the results of an analysis of the number, frequency and intensity of tropical nights in Ukraine. We have selected such weather stations that are located at different latitudes and correspond with the north, west, east, and south as well as the central part of Ukraine. This was done in order to analyse the differences in tropical nights across latitudes. Also we have weather stations located at the approximately one latitude to analyse how tropical nights vary in longitude. Data from weather stations for 1976-2019 were under analysis. We can say that the increase in the minimum air temperature during summer is on the whole territory of Ukraine. This leads to the fact that since the mid-1990s tropical nights begin to be observed in the east of Ukraine, as well as in the south. After 2000, tropical nights also have begun to be observed in the centre and even in the west of Ukraine. Between two half-periods (1976-1997 and 1998-2019) the increase of number of tropical night events in the south of Ukraine (up to 300 cases) is much more significant than the increase in their number in the northwest (up to 20 cases). As well as the frequency, the intensity of tropical nights also increases. There are cases with minimum daily air temperatures above 25°C. The analysis of the North Atlantic Oscillation (NAC) and the Mediterranean (Cairo-Algeria) indices in the context of explaining the tropical night’s occurrence in Ukraine turned out to be quite effective.