Climate projections of UTCI in the Czech Republic

A thermal stress on human is determinated by a combination of various meteorological variables, such as temperature, humidity, etc. Many indices have been created for the determination of level of thermal stress. Here, we select the universal thermal climate index (UTCI), which is created with the use of temperature, humidity, wind speed, and mean radiant temperature. The UTCI index can be acquired from observed data, however, the calculation of UTCI is also incorporated in some reanalyses and climate models too. Recently, it has been demonstrated that UTCI in central Europe increased in the last 30 years, with the largest increase detected in both summer and winter after 1990. While rising UTCI in winter reflects decreasing thermal stress on human, on the contrary, the rapid increase observed in summer indicates the opposite. The combination of rising temperature and humidity is the main cause behind the increase in the index. In this contribution, we bring the topic to the next level as we analyze the changes in UTCI in the Czech Republic for the entire 21st century. The future evolution of several meteorological variables, including the UTCI index, is incorporated in the Aladin-CLIMATE/CZ model, the domain of which covers the broad area of central Europe. Two scenarios are analyzed: SSP2-4.5 (the intermediate scenario) and SSP5-8.5 (the high scenario). It is evident that UTCI will rise in both annually and seasonally step over almost the whole Czechia, the largest increase being found in the lowlands regions of the country. The substantial increase in thermal stress arising from the changing meteorological conditions in the future is a concerning message, influencing lives of people, mainly in the urban areas.