A pair of NASA airplanes crisscrossing the skies and doing stomach-turning loops are giving scientists a 3-D look at winter air pollution in a way they've never had before.
The flights are part of a five-year, $30 million mission called DISCOVER-AQ, an effort to help researchers develop the next generation of satellites to measure air pollution from space. Jim Crawford, the mission's lead investigator from NASA's Langley Research Center in Virginia, explains how the airplanes work with monitoring stations on the ground to provide a better understanding of how air pollution forms and mixes.
The Valley's unique geography -- flat land ringed by mountain ranges -- and stagnant winter weather are the perfect lab for pollution research, Crawford said: "This is a great place to come."
The Valley is the second of four places in the U.S. where scientists are using the aircraft and ground stations to learn about pollution formation.
One of the planes, a four-engine P-3B Orion, has attracted considerable attention with its low-level passes and circles over and around Valley cities. Instruments on the plane measure the air quality at altitudes from below 1,000 feet up to about 9,000 feet.
At the same time, a smaller plane cruises at about 26,000 feet, using lasers and reflected light to simulate how an orbiting satellite sees the atmosphere over the Valley.
Tuesday was the fifth of 10 scheduled DISCOVER-AQ flights over the region, and the last before a weather front came through to help clean the air. When flights resume, perhaps as early as this weekend, scientists hope to examine how pollution forms from a clean slate and worsens with time in the region. "We arrived here at an ideal time for us," Crawford said.
Winter weather in the Valley creates an accumulation of very fine dust and chemical particles, compared with the summer, when chemicals that create ozone are more prevalent. But conditions can change daily or even hourly.
Ground stations operated by the San Joaquin Valley Air Pollution Control District and the California Air Resources Board give air-quality regulators a snapshot of what's happening on the Earth's surface. Satellites that pass overhead once a day offer a glimpse at the entire atmosphere at that particular time.
But satellites in space cannot distinguish whether pollution is in the upper atmosphere, near the surface, or somewhere in between.
"Trying to make a judgment about what the regulator wants to know -- which is what you're breathing on the ground -- and teasing that apart is not the easiest thing to do right now with satellites," Crawford said.
NASA's project is filling the gap.
The P-3B is festooned with probes that suck air as it climbs and descends. The probes connect to eight instruments that identify chemicals in the air and their concentrations at different altitudes. Scientists get a real-time look at the gunk that blankets the Valley between winter storms.
David Lighthall, health science adviser for the Valley air district, said the research will help his agency better predict pollution problems for the region's residents.
"They're laying the foundation for an improved model for both ozone and PM-2.5 (fine particles)," Lighthall said. "From these studies, they're collecting fine-grained meteorological information over time, to get different combinations of information that we can relate to our ground-level observations."
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