by Emily Schaller / OSAN AIR BASE, SOUTH KOREA /
Driving up a winding, bumpy road through a peaceful forest with tall pine trees towering over us, it was easy to forget that the megacity of Seoul was only 25 miles away.
This serene spot is the location of theTaehwa Mountain Forest Research site, one of the ground-monitoring “super sites” for the Korea US Air Quality (KORUS-AQ) study.
South Korea maintains a network of more than 300 air quality research stations across the peninsula. KORUS-AQ is making use of data from these ground sites and has added significantly to the instrumentation at two locations (Olympic Park and Taehwa Mountain) and dubbed them ground “super sites.”
The Taehwa site hosts a suite of air quality monitoring instruments from the Korean National Institute for Environmental Research (NIER), NASA, the University of California Irvine, Korea University, the U.S. Environmental Protection Agency and Aerodyne Systems.
One of the key issues for improving air quality forecasts is better understanding how human emissions from cars, power plants and industry interact with natural emissions from trees and plants. Although we usually think of forest air as being completely clean, chemical emissions from trees — called volatile organic compounds (VOCs) — are not always benign, especially when these emissions mix and react with urban emissions. These reactions can form ozone, a gas that is harmful to both human and plant health, as well as secondary organic aerosol particles. Understanding the complex chemistry taking place on the boundaries between urban and rural areas is important for better predicting and developing strategies for improving local and global air quality.
The Taehwa site, located in a mountainous forest, is the perfect location for addressing questions about how human-caused and natural emissions mix. The site boasts a 130-foot tower that reaches well above the tree line. Climbing the steps up the tower affords great views of the forest below and allowed us to see up close the air inlets and instrumentation placed at regular intervals along the tower.
At the base of the Taehwa tower are several structures filled with a variety of instruments that analyze the air collected at different heights along the tower as well as air collected by inlets at ground level. These instruments measure different VOCs as well as many other molecules and compounds important for unraveling the complex chemistry occurring at the site. In addition, instruments below the tower also analyze in detail small particles in the atmosphere, counting them and measuring their sizes.
In yesterday’s blog, I discussed how the DC-8 flies in spiral patterns to sample the air from near the ground up to 25,000 feet near Taehwa. By flying our KORUS-AQ aircraft near this site, we extend the reach of the air quality measurements from the top of the tower to nearly five miles up in the troposphere.
In addition to air quality and meteorological instruments at the tower, down the hill scientists from NASA Goddard Space Flight Center are measuring ozone above the site with the Goddard Ground-Based Tropospheric Ozone Lidar and with daily launches of balloons carrying instrumentation to measure ozone up into the stratosphere. The ground-based ozone instrument uses an infrared laser that shines from the top of a trailer up through the lower atmosphere and allows scientists to measure ozone concentrations up to several miles above the ground. This instrument is similar to the NASA Langley Airborne Differential Absorption Lidar (DIAL) being flown during KORUS-AQ on the DC-8.
Once a day the Goddard team launches a balloon outfitted with instrumentation to measure ozone along with temperature, pressure and humidity. These ozonesondes collect and transmit the concentration of ozone from the surface all the way up to about 19 miles, when the balloon pops and the ozonesonde falls back to Earth on a small parachute. The team launches an ozonesonde daily and will launch one during every KORUS-AQ flight to provide complementary data of ozone in the atmosphere below and above the altitudes of the planes.
After visiting the Taehwa ground site, meeting the students and researchers working there, learning about their instruments, watching an ozonesonde launch into the stratosphere, and climbing up the research tower (which forced me to overcome a slight fear of heights), I was struck by the diversity of people, instruments and platforms (aircraft, ground, balloons, satellites) that have been brought together to try to solve the problem of poor air quality.