The role of shading on biometeorological indices in the centre of Prague
Prague is the capital and the largest city of the Czech Republic and its historic centre near the Vltava river is a popular tourist destination. Especially the area along the right bank of the Vltava river, called Náplavka, is one of the most popular locations to visit during the summer months due to many social and cultural events that take place here. However given the north-south orientation of the Vltava river and the lack of greenery and shade in this area, the question arises as to what extent thermal conditions are comfortable during hot summer days at Náplavka. Many previous studies have shown that the presence of greenery and shade is essential for reducing the heat stress in the streets.
We did a study where we assessed the effect of shading on biometeorological conditions at eight different measuring sites located along a loop between Charles Square and the Náplavka riverbank. We used a Kestrel 5400 heat stress tracker, to measure and record meteorological parameters (including air temperature, relative humidity, wind speed, Heat Index, Wet-Bulb Globe Temperature) every two hours between 8:00 a.m. and 6:00 p.m. CEST on 16 summer days from 2019 to 2022. In addition, fisheye photographs were taken at each location in order to quantify the effect of shading. From these data, we calculated advanced thermal comfort indices (Physiologically Equivalent Temperature, Universal Thermal Climate Index) and Sky View Factor (SVF) in the RayMan Pro program. SVF is a shading factor, which is calculated from fish eye photographs. It is an indicator of shadow density and it reaches values from 0 to 1 (1 is completely shaded).
You can see a study area here. It is a loap with eight measuring sites and the first and the last site is same.
Our results showed that while in the morning Náplavka’s biometeorological conditions were most comfortable among all measurement sites, they became most stressful in the afternoon. The analysis of the fisheye images showed that the lack of greenery and shading at Náplavka contributed significantly to the high heat stress levels. Our results suggest that the relocation of day-long events from Náplavka to other locations (e.g. a park at Charles Square) should be considered and/or adequate sun protection should be provided on hot summer days.
