Long-term biometeorological conditions in the mid-sized European city – A case study of Banja Luka (Bosnia and Herzegovina)

Intensive urbanization and global warming are impacting the health and well-being of urban population. Nevertheless, urban environments with different design will have different micro and local climate conditions. Therefore, the application of parameters that assess thermal stress in urban areas, such as outdoor thermal comfort (OTC) indices are of paramount importance.

In this study the long-term (1961–2020) datasets of daily OTC indices for the city of Banja Luka (Bosnia and Hercegovina) were used. Detailed temporal analysis using Physiological Equivalent Temperature (PET), Universal Thermal Climate Index (UTCI) and Mean Radiant Temperature (Tmrt) was performed for: a) the entire research period, b) the decadal level, and c) defined extreme heat/cold stress categories. The results show intensive increase in extreme/strong heat days in the last twenty years, and the number of these days is five times higher than in the 70s and 80s. Decreasing tendencies are noticed in extreme/strong cold days towards the last two decades.

We also performed modeling of changes in mean daily air temperature according to IPCC climate scenarios RCP 2.6, RCP 4.5 RCP 8.5 until the end of the XXI century. The results point to significant positive changes under all three climate scenarios.

Furthermore, we analyzed PET, Tmrt and modified Psychologically Equivalent Temperature (mPET) indices during the hot summer days in June 2021 for different urban spaces (downtown, urban park, riverside) in Banja Luka. Results show that the downtown is the most most uncomfortable area in terms of OTC indices. Also, riverside had lower average T_aduring summer daytime compared to urban park and downtown likely due to the synergy between river cooling effect (evaporation and sensible heat transfer) and tree shade.