Assessing the potential of Urban Greenery to adapt to climate change intensified UHI during heatwaves in Humid Continental Climate climate zones using Long-Term Data and Geospatial Analysis.

Despite the increasing trend of temperatures due to climate change, urban areas often experience higher temperatures than rural areas, a phenomenon commonly referred to as the Urban Heat Island (UHI). Heat waves are becoming more frequent in Turku, Finland (humid continental climate zone), and longer and warmer days are being experienced in summer than in nearby rural areas. The use of heat-absorbing materials in construction, increased impervious surfaces, higher emissions of CO2, and lack of blue-green regions in the urban territory, etc., are found to accelerate this phenomenon. Green infrastructure or urban green parks are expected to moderate temperature fluctuations by absorbing less heat and providing cooling through evapotranspiration, thereby slowing down temperature changes in urban environments.

In this research, the impact of urban greenery to mitigate UHI during heatwaves in the city of Turku, South-West Finland, was studied. We exploited spatially and temporally comprehensive temperature observation data over the urban area, and precise land use data to analyze the relationships between UHI and UG. A total of 22 temperature monitoring stations, recording temperatures every 30 minutes from 2002 to 2024, were used. The land cover in 2022 was obtained from an open 2m resolution land cover dataset produced by SYKE (Finnish Environment Institute). Satellite images were used to detect the change in land cover since 2002.

Statistical methods were used to find temperature-increasing trends at each logger station point to observe and analyze how urban greenery can influence or control temperature fluctuations. The neighborhood of several logger stations underwent changed land use (forestry to residential blocks with impervious surfaces). How this urbanization influenced the microclimate change in the city will be analyzed. Also, changes in the duration and magnitude of heat waves from 2002 to 2023 are expected to be studied.

Nature-based Solutions (NBS), especially urban green (UG) infrastructures, are becoming popular also in Nordic countries to increase climate change resilience, reduce the risk of urban flooding, improve public well-being, better immune systems, and urban biodiversity. However, not many studies have been done examining urbanization, UG, heatwaves, and UHI, especially in humid continental climate zones. This study aims to deepen the understanding of the effect of urban greenery on UHI, and how they control temperature in neighborhoods during heatwaves in Turku. The outcomes of these results may help city planners design city expansion in a way that makes it resilient to future climate change-intensified heatwaves in the same climate zone.