Urban versus lake impacts on heat stress and its disparities in a shoreline city

Abstract Shoreline cities are influenced by both urban-scale processes and land-water interactions, with consequences on heat exposure and its disparities. Heat exposure studies over these cities have focused on air and skin temperature, even though moisture advection from water bodies can also modulate heat stress. Here, using an ensemble of model simulations over Chicago, we find that Lake Michigan strongly reduces heat exposure and heat stress (wet-bulb globe temperature) during the day, while urbanization enhances them at night. We also demonstrate that urban and lake impacts on temperature (particularly skin temperature), including their extremes, and lake-to-land gradients, are stronger than the corresponding impacts on heat stress, partly due to humidity-related feedback. Likewise, environmental disparities across community areas in Chicago seen for skin temperature are much higher than disparities in heat stress. The results call for consistent use of physiologically-relevant heat exposure metrics to accurately capture the public health implications of urbanization.