What we showed in our work is the importance of taking into account the spatial variability of cities -- the unique features that make Paris Paris and London London," says Marco Giometto, the first author of the study. "Most city representations used in weather models are based on data obtained from tower measurements made at a particular location within the city, which current models approximate as a rough patch of land. The transport of heat, humidity, or pollutants is then computed using mathematical relationships. These relationships implicitly assume that the city is geometrically regular, which is a stringent assumption," he says.