February 25, 2010 | The greater Salt Lake City area is known for harboring some of the most polluted air in the country during the winter. A team of NCAR researchers is gearing up to collaborate on a study of the winter weather inversions that cause the city's poor air quality. The research is expected to be applicable to other cities that experience similar atmospheric conditions.
An inversion occurs when the atmosphere's normal temperature profile is reversed, so that rather than air decreasing in temperature with altitude, a layer of dense, cold air underlies lighter, warmer air. A snowstorm followed by clear skies can prime the atmosphere for these conditions in Salt Lake City. Cold air—and the city's pollutants—become trapped in a pool near the valley floor, rather than mixing vertically in the atmosphere.
The cornerstone of the three-year study is a field component, called the Persistent Cold-Air Pool Study (PCAPS), scheduled for December 2010 through February 2011. Researchers will collect observations, analyze data, and use atmospheric models to study the formation, maintenance, and dissipation of Salt Lake City's cold-air pools.
About a dozen researchers from NCAR's Earth Observing Laboratory will be in Salt Lake City during PCAPS to set up and run a variety of instruments, including a 33-foot (10-meter) tower for measuring wind, temperature, humidity, and turbulence at four heights; several portable stations for observing all components of surface energy; radars for recording wind and temperature; and a portable GPS weather balloon system. Students from the University of Utah will help with balloon launches.
"Much of our work is in rural areas and involves storm chasing," says scientist Bill Brown. "Working in an urban environment during calm weather will give this project a different flavor."