Analyzing the Influence of Urban Forms on Surface Urban Heat Islands in Europe

Problem: Remotely sensed land surface temperatures help exploring the surface urban heat island. Measures to mitigate the urban heat island include increasing green urban areas and altering the form of cities. Research is needed to explore the impacts of urban form on the surface urban heat island. Research strategy: Data on land surface temperatures for summer 2001 and land cover are combined with meteorological, demographic, and topographic data for European urban regions, delineated as larger urban zones. To ensure a comprehensive view, three ways of quantifying surface urban heat island are calculated and stratified for morning and evening, and climate zones. Linear models reveal the relative influence of the four factors: (1) composition (e.g., share of different land covers in the urban region), (2) configuration (e.g., spatial arrangement), (3) location (e.g., distance to coast or elevation), and (4) population. Findings: The explanatory power (i.e., adj. R-sq) of the models varies strongly among the different ways to quantify the surface urban heat island and time of day. Rather specific combinations of explanatory variables were found to be relevant in explaining the variation in the different ways of quantifying surface urban heat islands. Compact urban form increases the surface urban heat island measured in one way, but was not a significant predictor for other ways of quantification. Increasing the share of built-up area and forest both increase the surface urban heat island. More built-up areas increased the mean temperature in the region, whereas more forest unsurprisingly decreased the overall temperature. The three ways of quantifying the surface urban heat island were correlated at r<0.5, and their variation was explained by different variables implying that they carry different information about the surface urban heat island effect. Takeaway for practice: Considerable attention needs to be paid to the aims of spatial planning, because mitigating the surface urban heat island might lead to measures that are actually increasing mean temperatures.