Mitigating Effect of Urban Green Spaces on Surface Urban Heat Island during Summer Period on an Example of a Medium Size Town of Zvolen, Slovakia

Climate change affects the urban population’s health and quality of life. Urban green spaces (UGS) underpin several essential ecosystem services, amongst them climate regulation. Urban vegetation mitigates high temperatures and, thus, reduces the heat stress for urban residents. The study aimed to verify whether the Surface Urban Heat Island (SUHI) effect manifests itself even in a medium size town (Zvolen, Slovakia) surrounded by agricultural and forested landscape and to quantify the temperature mitigating effect of urban green spaces. Land surface temperature (LST) and SUHI distribution were derived from the Landsat data during the summer months of 2010–2021. To statistically prove the cooling effect of the urban vegetation, we tested (by one-way ANOVA) LST within three urban zones of the Zvolen municipality defined by the Copernicus imperviousness density data: (a) dense urban area (31–100% impervious surfaces), (b) discontinuous urban area (1–30% impervious surfaces), (c) urban green spaces (0% impervious surfaces), and the open land surrounding the town (0% impervious surfaces). The results showed a statistical difference in temperatures between all urban areas (all zones) and the open land. Moreover, the UGS temperature was statistically different compared to the other urban zones. The mean temperature difference through the years 2010–2021 between urban green spaces and the dense urban area was 3.5 °C, with a maximum of 4.9 °C and a minimum 1.7 °C in favor of the urban spaces. Moreover, the temperature of urban green spaces and open land varied during the studied summer period. The warmer the weather, the higher the difference, while at the end of August, on a notably colder day, there was no significant difference between them. The results confirmed that UGS are significantly cooler during hot days, and they can mitigate the local climate

Mitigating Effect of Urban Green Spaces on Surface Urban Heat Island during Summer Period on an Example of a Medium Size Town of Zvolen, Slovakia

Climate change affects the urban population’s health and quality of life. Urban green spaces (UGS) underpin several essential ecosystem services, amongst them climate regulation. Urban vegetation mitigates high temperatures and, thus, reduces the heat stress for urban residents. The study aimed to verify whether the Surface Urban Heat Island (SUHI) effect manifests itself even in a medium size town (Zvolen, Slovakia) surrounded by agricultural and forested landscape and to quantify the temperature mitigating effect of urban green spaces. Land surface temperature (LST) and SUHI distribution were derived from the Landsat data during the summer months of 2010–2021. To statistically prove the cooling effect of the urban vegetation, we tested (by one-way ANOVA) LST within three urban zones of the Zvolen municipality defined by the Copernicus imperviousness density data: (a) dense urban area (31–100% impervious surfaces), (b) discontinuous urban area (1–30% impervious surfaces), (c) urban green spaces (0% impervious surfaces), and the open land surrounding the town (0% impervious surfaces). The results showed a statistical difference in temperatures between all urban areas (all zones) and the open land. Moreover, the UGS temperature was statistically different compared to the other urban zones. The mean temperature difference through the years 2010–2021 between urban green spaces and the dense urban area was 3.5 °C, with a maximum of 4.9 °C and a minimum 1.7 °C in favor of the urban spaces. Moreover, the temperature of urban green spaces and open land varied during the studied summer period. The warmer the weather, the higher the difference, while at the end of August, on a notably colder day, there was no significant difference between them. The results confirmed that UGS are significantly cooler during hot days, and they can mitigate the local climate

Quantification of the Cooling Effect and Cooling Distance of Urban Green Spaces Based on Their Vegetation Structure and Size as a Basis for Management Tools for Mitigating Urban Climate

The urban climate is receiving increased attention mainly due to climate change. There are several ways to mitigate the urban climate, but green spaces have an advantage over other cooling systems because, in addition to their climate function, they provide several other ecosystem services that enhance the sustainability of urban systems. The cooling effect of green spaces varies depending on their species composition, the structure of the vegetation, the size and shape of the green spaces or the specific characteristics of the plants. Therefore, the exact quantification of urban green space’s cooling effect is of critical importance in order to be effectively applied in urban planning as a measure of climate change adaptation. In this paper, we quantified the difference in the cooling effect between urban green spaces depending on their vegetation structure (grass versus trees) and their size, and assessed to what distance from the urban green space its cooling effect can be observed. Urban green spaces were identified using Landsat orthophotomosaic and airborne laser scanning. The urban temperature was calculated as the land surface temperature (LST) from Landsat data using a single-channel method. To quantify differences in the magnitude of the cooling effect of green spaces and the distance from the edge of the green space over which the cooling effect occurs, we used a one-way analysis of variance and regression analyses. Our results show that the cooling intensity, as well as the cooling distance, are dependent on the size and structure of the green space. The most significant cooling effect is provided by large green tree spaces, where the cooling intensity (difference of LST compared to an urban area without vegetation) was almost 4.5 °C on average (maximum almost 6 °C) and the cooling distance was significant up to 90 m (less significantly up to 180 m). Large grass spaces and medium tree spaces have similar effects, with a higher cooling intensity (2.9 °C versus 2.5 °C on average) however, the cooling effect extends to a greater distance (up to 90 m) for medium tree spaces compared to large grass spaces, where the cooling effect only extends to 30–60 m. Small areas with trees and medium and small grass areas without trees have an average cooling intensity below 2 °C