The proliferation of paved surfaces in urban areas — including strip malls, subdivisions, and parking lots — can alter weather patterns in a way that keeps pollutants trapped over cities rather than allowing them to be blown out to sea, a new study says. Researchers combined extensive atmospheric measurements taken over Houston during a nine-day heat spell with computer simulations, and discovered that the contrast between overnight land and sea temperatures was reduced because paved areas were absorbing so much heat during the day. As a result, nighttime winds that would have otherwise blown pollutants out to sea were reduced, and air above the urban areas remained stagnant, according to the study, which will be published in the Journal of Geophysical Research-Atmospheres. Researchers say the findings could have implications for design of fast-growing cities along coastal areas. “If the city continues to expand, it’s going to make the winds even weaker in the summertime, and that will make air pollution much worse,” said scientist Fei Chen of the National Center for Atmospheric Research in Boulder, Colo. and lead author of the study.