Study Says Urban Heat Islands Worsen Smog

The urban heat island effect created by large areas of pavement and buildings can cause many problems, from increased energy use to reduced water quality. A new study from the National Center for Atmospheric Research (NCAR) suggests that expanses of paved surface may also worsen air quality in coastal cities like Houston, where the research was focused.

Because hot pavement and buildings continue to radiate heat even after the sun goes down, city air stays warm, preventing strong offshore breezes from forming. Such breezes would normally circulate over grasslands or croplands to help cleanse the air of pollutants. Weaker breezes cannot penetrate the urban landscape, so pollution remains in the warm, stagnant air. Drought conditions can cause similar effects, the study found.

Future research will focus on other rapidly growing coastal cities to determine whether topography, climate, and other factors also affect the formation of strong ocean breezes.