Factors influencing the subsurface urban heat island in the city of Wrocław (Poland)

The growing average air temperature and rapid urbanization deepen the urban heat island (UHI) phenomenon, which mainly affects large cities. Urban areas contribute to changes in the local atmospheric environment but also groundwater. The impact of these changes on the thermal regime of groundwater is documented all over the world by the increased temperature of groundwater in city centers compared to the surrounding rural areas. However, this relationship as well as the impact of other factors on the subsurface urban heat island (SUHI) are not yet well understood. In the case of the city of Wrocław, characterized by an increase in average temperatures in recent decades and the identified UHI phenomenon, present-day the phenomenon of SUHI is unknown.

This work focuses on the analysis of maps of the spatial distribution of groundwater temperature in the city of Wroclaw (Poland), obtained using spatial interpolation. For this purpose, measurement data from 2004-2005 and 2022-2023 were used. In addition, an attempt has been made to compare the distribution of groundwater temperature with the Land Surface Temperature (LST) for each of the periods. In the next part of the work, the relationships between groundwater temperature and other factors such as: distance from the city center, distance from rivers, LST and UHI were determined. Generalized linear regression was used to indicate which factors influence the subsurface urban heat island (SUHI). The highest rate was given to the distance from the city center (R2=0.49).