Earth & Sky

Local weather and terrain

JB: This is Earth and Sky, on how some places are more susceptible to air pollution due to local weather and terrain.

DB: For example, the United States produces about one quarter of the world’s air pollutants, but they don’t all stay here.

Di Girolamo: For much of rest of the country we don’t have such high pollution episodes because the topography and meteorology is such that the concentrations of aerosols just don’t build up here.

JB: That was Larry Di Girolamo, at University of Illinois. He’s using data from an instrument called the Multi-angle SpectroRadiometer aboard a satellite to study air pollution.

DB: He found concentrations of aerosols in the Ganges Valley in northern India that were five times higher than typical levels in Los Angeles. That’s partly due to the greater population in the Ganges Valley.

JB: But, in addition, winds carry pollutants from far away sources into the area. These pollutants are trapped by the surrounding mountains as well as a high pressure system that sits on top of the valley for the winter months.

Di Girolamo: In India, however, particularly in the Ganges Valley, they have the combination of topography, meteorology, and a third of a billion people all living in that valley, all contributing to this high pollution episode that we observe.

_DB: Scientists are now studying the impacts this air pollution will have on human health and Earth’s climate. Our thanks to NASA explore, discover, understand. We’re Block and Byrd for Earth and Sky.