Month-Long Study Targets Improved Air Quality Forecasting
Throughout September, Houston air quality measurements taken by mobile labs, ground instruments, airplanes, and a satellite will help scientists understand how to better interpret and forecast air quality using satellite data and numerical models.
The effort is part of a multi-year NASA air quality study, DISCOVER-AQ, which also includes measurements in Washington, D.C., Baltimore, Los Angeles, and Denver. University of Houston atmospheric scientists, Barry Lefer, Robert Talbot, Yunsoo Choi, and adjunct professor Gary Morris are participating in the project along with 15 UH undergraduates and graduate students.
Map of Houston 2013 DISCOVER-AQ Campaign. Two NASA aircraft will fly over the Houston area through September, one as low as 1,000 feet, to measure air pollution with a number of onboard science instruments. (Image Courtesy of NASA)
Presently, it is difficult to accurately measure surface air quality based on satellite data.
“Satellites measure the total amount of pollution in the atmosphere, so the readings get the upper level pollutants that don’t affect us as much, as well as the lower level pollutants,” said Barry Lefer, associate professor in the Department of Earth and Atmospheric Sciences. “The trick is how do you subtract off the stratosphere to get to the measurements that you want?”
Massive Air Quality Data Collection
For 10 to 13 days in September, scientists are collecting an enormous amount of data similar to what a satellite measuring air pollution would collect.
Two NASA aircraft equipped with scientific instruments are flying a fixed route over Houston gathering air quality data. Simultaneously, five mobile labs equipped with similar devices are driving approximately the same route. Measurements are also being made at stationary locations around Houston and with weather balloons.
The satellite measurements are being made by a fleet of Earth-observing satellites, called the Afternoon Constellation or “A-train,” which passes over Houston each day at 1:30 p.m.
“UH has two mobile labs, instrumentation at 6 of the 15 ground sites, and daily weather balloon launches gathering ozone measurements,” said Lefer. “We are also hosting several monitoring devices from other universities on our rooftop lab at Moody Towers and in our mobile labs.”
Members of the UH mobile lab team (from left) James Flynn, Xin Lan, Robert Talbot, and Barry Lefer with Rice University participant, William Wallace. The sampling area covers the Houston metropolitan area ranging from Conroe in the north to Galveston in the south. “The flight path is sort of a figure eight shape,” Lefer said. “The planes fly the route three times each flight day. With 10-13 flight days, we’re going to get good statistics; some flights will be on clean air days and some on dirty days.”
One of the NASA planes flies at 26,000 feet taking downward gaseous and particulate measurements mimicking a satellite. The other plane flies a similar route at lower altitudes and also makes spirals around eight locations sampling the air at various levels over those sites. UH’s Moody Towers is one of the spiral locations.
Moody Towers Measurements
“On flight days, there are three flights over campus at approximately 10 a.m., 12:30 p.m. and 3 p.m.,” Lefer said. “The plane flies around Moody Towers starting at 1,000 feet and making about 3-4 spirals as it climbs to 12,000 feet. The spiral is big, about 2-1/2 miles in diameter.”
Moody Towers also has instrumentation on its roof that is measuring everything the plane is measuring and more. Some of the instrumentation is there year-round and other devices belong to visiting scientists from Baylor University, Texas A&M University, University of Colorado, Pennsylvania State University, Appalachian State University, the Environmental Protection Agency, NASA, USDA, and NOAA. UH’s mobile labs also hold equipment from Chalmers University (Sweden) and Rice University.
On Moody Tower, Talbot’s instrumentation is measuring carbon dioxide, methane and mercury, and Lefer is measuring ozone, formaldehyde and four other pollutants.
Adjunct professor Gary Morris and UH undergraduates Erika Marrero and Daniel Sierra prepare to launch a weather balloon outfitted with ozone measuring equipment. Launches from UH occur every day in September. Choi’s air quality forecasting model is helping the NASA project team reach its decision each afternoon on whether to fly the planes the next day. Morris is launching weather balloons outfitted with ozone measuring equipment each day from campus.
“The results of this study are going to help us get a better understanding of what the satellite is showing us,” Lefer said. “If we are better able to interpret satellite data, then we can make more accurate air-quality analyses and forecasts. And, that will have a big impact on human health.”
University of Houston’s participation is funded by grants from the Texas Air Quality Research Program and the Texas Commission on Environmental Quality.
- Kathy Major, College of Natural Sciences and Mathematics