How much of the summer surface-temperature inequality in European cities can urban form explain?

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Rapid urbanization and growing heat stress have made it important to understand the association between urban form and environmental inequality, but comprehensive insights have been lacking. The researchers studied the population-weighted Gini coefficient, a measure of inequality, for average summer land surface temperature (LST) in 683 European cities, defined as Functional Urban Areas.

They examined it against 34 urban form indicators: population, area, compact ratio, local climate zones (LCZ), presence of grass, impervious surfaces, trees and water, albedo, elevation, aspect, Köppen-Geiger climate classification (KG), and latitude. They calculated density, Moran's I and entropy measures to quantify cities' spatial structures and diversity. Each city was divided into 1 × 1 km spatial units, and inequality among those units was calculated.

Using geographically weighted regression (GWR), the researchers found that the influence of factors varied across cities and that urban form could explain almost 70% of overall inequality. Population density and concentration, LCZ 9, dry climate and high latitude were variables that occasionally decreased LST inequality. Variables associated with increases were urban size, LCZ 3, 5, 6 and 8, LCZ entropy, the density and concentration of impervious surfaces, trees, high elevation, southwest aspect and polar climate. The study discusses the findings and proposes spatial strategies to mitigate inequality.