Human Thermal Comfort Conditions during Heat Wave Events in Kyiv, Ukraine

Abstract

Assessment of the big cities bioclimate during heat wave (HW) events is a highly topical issue and a focus point for many researchers. Reliable results of the assessment of heat stress (HS) intensity during HWs form the basis for the development and implementation of heat adaptation measures. In Ukraine, first HW studies started only a few years ago, and the thermal comfort conditions during these atmospheric phenomena have not been explored yet. The purpose of this article is to assess characteristic features of thermal bioclimate in Kyiv during heat wave events. The assessment is based on the thermal index – physiologically equivalent temperature (PET). The RayMan model was used to simulate PET values. As shown in the study, during the period of 1961–2020, 24 heat wave events were observed in Kyiv. Those HWs were characterized by different duration (from 6 to 18 days) and intensity (with the maximum value of cumulative Ta,MAX 108.6°C). Thermal comfort conditions registered during heat waves were characterized by heat stress varying from slight (23.7°C) to extreme (47.0°C). To assess the impact of HWs on the human, a classification based on mean PET values during a single heat wave and its duration was proposed. According to this classification, heat waves belong to three following grades: HWs with moderate, strong, and extreme HS. Analysis of HW events in Kyiv for the research period demonstrates four (4) heat waves with moderate heat stress, nineteen (19) with strong stress, and one (1) with extreme stress (specifically, the heat wave in late July–first half of August 2010). The daily PET values at 12 UTC during this HW varied from 37°C to 47°C and were much higher than mean PET values for these days during 2005 and 2014.