Clearing the Air: NASA and the EPA Work to Understand the Quality of the Air We Breathe
A warm and cozy fireplace is the perfect setting on a cold winter night. As you curl up in front of your fire however, you probably aren't thinking about asthma, heart attacks, or even cancer. But, the Environmental Protection Agency (EPA) warns that wood-burning appliances and fireplaces generate smoke and may emit large quantities of air pollutants containing hundreds of harmful chemical compounds.
The EPA is working with NASA to improve what we know about the air we breathe.
The two agencies recently completed a short but intense field campaign to study air quality in the San Joaquin Valley in central California. Using instruments on aircraft, satellites, and at ground sites, scientists are working to improve observations and understanding of air quality in this region, an area that is plagued with air pollution.
Image right:The flight track for the campaign. The EPA and NASA researchers flew this same path each day of their mission. Click on the image to see a larger format version. Credit: NASA
"The San Joaquin Valley has some of the highest concentrations of fine particulates in the nation," said Jim Szykman, an EPA research scientist working at NASA Langley Research Center in Hampton, Va. "The wintertime is when these concentrations, or poor air quality days, can be really bad because of a lot of factors, including, we believe, wood burning for heat, as well as meteorological processes like temperature inversions."
A temperature inversion means there is a cooler air mass near the ground and warmer air at higher altitudes. This atmospheric condition is usually caused by a passing cold front or from the invasion of sea air by a cooler onshore breeze, which is typical of the wintertime conditions in central California. Because of central California's location – the ocean to the west and mountains to the east – wintertime temperature inversions can cause pollutants to get trapped because lower level cool air does not rise and then disperse like warm air.
Szykman and Rebecca Rosen, also from the EPA, are the co-principal investigators for the San Joaquin Valley Advanced Monitoring Initiative. Together the EPA and NASA are using a suite of instruments to study atmospheric particles, called aerosols, which come from many sources: burning wood; vehicles; construction and agricultural activities; and stationary sources such as refineries.
During the campaign, researchers flew an advanced laser instrument called the HSRL (High Spectral Resolution Lidar) on a NASA King Air B200 aircraft, based at NASA Langley. The lidar instrument is an innovative technology that is similar to radar. Instead of the radio waves that radar uses to determine and map locations, directions and speeds, lidar uses laser light.
Image left: Inside the King Air B200, Dave Harper from NASA Langley monitors the instrument as it makes measurements of the air above the San Joaquin Valley in central California. Credit: EPA
The King Air is specially equipped so that the researchers can transmit the laser out of a window in the bottom of the airplane and use a telescope to measure the amount of light that scatters back from aerosols and other atmospheric components like water droplets in clouds. The HSRL technique allows researchers to make quantitative optical measurements of the vertical distribution of particles in the atmosphere.
"HSRL allows scientists to infer the likely sources of particulates," said Chris Hostetler, co-principal investigator for the instrument along with John Hair and Rich Ferrare, all of NASA Langley. "For example, we can differentiate between urban pollution and soil dust."
Originally, another NASA Langley instrument, the Compact Aerosol Lidar, was proposed to fly during this field campaign. However, because of a combination of factors the instrument was unable to fly, and the HSRL was chosen as a replacement, showing "the flexibility of our researchers and our ability to fix problems with multiple approaches," said Russell DeYoung, the principal investigator for that instrument.
Ultimately working to improve forecasts of air quality in the San Joaquin Valley, the NASA and EPA researchers are first trying to improve satellite measurements of aerosols.
Image above: HSRL data from February 15, 2007 with geographic reference points noted. The HSRL gives the vertical perspective of the atmosphere, showing that the high aerosol concentrations (shown in red) are near the ground layer. Click on the image to see a larger format version. Credit: NASA/LaRC/EPA
Right now, researchers use aerosol measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS), an instrument on the NASA Terra and Aqua satellites. But, the terrain in the San Joaquin Valley makes it more difficult for MODIS to make accurate measurements of aerosols in this region. Another challenge with MODIS is that researchers cannot see where the particles are located vertically. They can only obtain measurements for the total column of the atmosphere, from the ground all the way to the upper atmosphere. Together, the lidar and MODIS instruments can determine whether this column has a high concentration of pollution and whether that pollution is further up in the sky or at the ground level, where the majority of the population lives and breathes.
"We are working with the MODIS science team – specifically Allen Chu at University of Maryland - Baltimore County – to try to improve the aerosol product in a part of the country where MODIS air quality measurements are more uncertain," said Jay Al-Saadi of NASA Langley. "We want people to be able to use NASA satellite data to reduce issues that affect our lives."
Image right: MODIS aerosol data from Feb. 15, 2007, with geographic reference points noted. The Pacific Ocean is at the bottom left of the image and the Sierra Nevada mountain range is at the top right. The aircraft flew the path, from Stockton to Bakersfield each day. Each of the cities listed on the image has a ground site so that the aircraft, the satellite and the ground instruments can be compared. Credit: Allen Chu/UMBC/NASA
"The aerosol measurements from MODIS will to help us better understand the distribution of aerosols in the San Joaquin Valley,” the EPA’s Carol Bohnenkamp explained further. The scientists will use this knowledge to evaluate air quality models, which state and local agencies rely on to determine the best strategies for achieving clean air in the valley.
"The measurements also have the potential to give us a better understanding of the current ground-based aerosol measurements and emissions inventories," Bohnenkamp added.
Through this field campaign and other efforts during the "Advanced Monitoring Initiative," the EPA is improving its understanding of how environmental factors affect human health and ecological well being. Projects from this initiative will enable a better understanding of how to improve data to support and enhance environmental policy, management, and decision making.
+ EPA Region 9 Web Site
+ EPA Web Feature and Captioned Video on the field campaign
NASA Langley Research Center