19 June 2013
modified from the story by CIRES Communications
Many photographs of the Southeast's Smoky Mountains show layers of tall hills, shading to purples and grays in the distance. Tiny particles in the atmosphere help create the effect, which makes for stunning pictures. But human-caused enhancements of those fine particles also contribute to poor air quality in the Southeastern U.S., and may help explain why the region has not warmed like the rest of the nation.
So this summer, scientists from CSD and colleagues from dozens of other institutions are taking one of the most detailed looks ever at the natural and manmade emissions that affect air quality in the Southeast, and their movement and chemical transformations within the atmosphere. The Southeast Nexus (SENEX) mission should help scientists determine the origin of the fine particles and how they contribute to the haziness in the region and affect regional air quality and temperature trends.
Both the natural environment and human activities contribute to haziness in the Southeast. Plants and trees give off gases called organic compounds (VOCs) that can react with manmade emissions in the atmosphere to create pollutants such as ozone and the tiny particles known as aerosols—the building blocks of haze. Power plants, refineries and other industrial sources also give off gases that lead to haze formation. The fine particles, known as aerosols, don't simply diminish air quality and create visibility problems—they also affect the regional climate. Many aerosols reflect light coming directly from the sun and contribute to the formation of clouds that in turn reflect sunlight. In the Southeast, is the result a cooling influence, which has partially offset the warming effect of greenhouse gases?
"The Southeast has the highest natural emissions in the Nation, and also has high manmade emissions, humidity and cloudiness," said CIRES atmospheric scientist Joost de Gouw working at CSD. "The question is how all these ingredients combine and react to form a summertime haze that impacts air quality and may cool the climate."
To investigate the complex processes in the atmosphere in the Southeast, CSD and other scientists are using a battalion of state-of-the art instruments that measure critical variables such as the types and concentrations of chemicals and aerosols, and the wind, temperature and moisture. One of NOAA's WP-3D Orion research airplanes has been outfitted as a flying chemical laboratory for the mission and the aircraft and scientists will fly throughout the southeastern skies sampling air chemistry from Texas to the Atlantic Ocean and from the Ohio River Valley to the Gulf of Mexico.
"This mission may help crack key mysteries that have stumped air quality experts and climate scientists for decades. It's an impressive effort happening in the sky and on the ground that will bring valuable information to policy makers, scientists, and the public alike," said Steve Fine, Ph.D., deputy assistant administrator for NOAA Research.
The NOAA WP-3D research aircraft is the main instrument platform for the SENEX study, which focuses on the interactions between natural and human-caused emissions at the nexus of climate change and air quality. SENEX, based out of Smyrna, TN, is conducted in close collaboration with colleagues from other agencies and academia under the umbrella of the Southeast Atmosphere Study (SAS). SAS is a six-week scientific investigation of the Southeast's atmosphere, involving NOAA, the National Science Foundation, the Environmental Protection Agency, Electric Power Research Institute, and dozens of other domestic and international institutions. Taken together, the projects comprise the most detailed look ever at the natural and manmade emissions that affect air quality in the Southeast.
As part of the SAS study, three other aircraft – the NSF/NCAR C-130, the Purdue University Duchess and the Stonybrook University Long-EZ – will also be measuring the vital statistics of the atmosphere. SAS also includes key ground-based experiments, at Brent, AL; Birmingham, AL, Look Rock, TN; and Research Triangle Park, NC. The instrumentation tower at Brent provides measurements of nearly 100 chemical species and aerosols from near the surface up to 20 meters above the ground.
"The last time an atmospheric study of this size took place in the Southeast was in the late 90s," de Gouw said. "Since then, power plants and motor vehicles have become much cleaner, and it will be important to document how the atmosphere has responded to these changes."