A new study from the National Center for Atmospheric Research documents how Houston’s vast expanse of paved surfaces allows the city to hold onto locally developed air pollution for longer periods of time, and prevents breezes that would otherwise naturally develop from sending all that nasty smog and stuff to outlying areas. Concrete and asphalt paving helps by soaking up heat during the daytime. This keeps land areas relatively warm overnight, which means there’s a lower contrast between land and sea temperatures during the summer. The result? Much less of those smog-stealing nighttime summer breezes. During the daytime, Houston buildings help to block local winds and keep things more still in the afternoon. Just another way standard development practices allow Houston to be a responsible steward of its own locally produced airborne products.
The study’s lead scientist, NCAR’s Fei Chen, projects that continued paving in the Houston area will help to still those messy, pollution-distributing breezes even further. The alternative, Chen suggests — adding more green spaces to the city or putting in lakes or ponds — would likely reduce nighttime temperatures, cause winds to pick up, and spill valuable Houston-born particulates over the Gulf of Mexico.
One computer simulation run by the scientists paints just such a nightmare scenario of a smog-spewing city: “If Houston were covered with cropland instead of pavement . . . inland air would heat up more than marine air during summer days and cause a sea breeze to blow onshore in the afternoon. Conversely, as the inland air became cooler than marine air overnight, a land breeze would blow offshore—potentially blowing away pollution.”
The scientists’ report, entitled “A numerical study of interactions between surface forcing and sea-breeze circulations and their effects on stagnation in the greater Houston area,” was developed with support from the U.S. Air Force Weather Agency, the U.S. Defense Threat Reduction Agency, and the National Science Foundation. It’ll hit the newsstands in the next edition of the Journal of Geophysical Research–Atmospheres.
Illustration: UCAR/Lex Ivy