Capturing a complex ‘snapshot’ of air pollution in California

By UC Office of the President and UCLA Today
Originally posted in UCLA Today

When geologists want to catalogue California’s rock layers, they bring a few axes, a compass and broad-brimmed hats. When biologists want to understand birds, they need decent binoculars and good hiking boots. But when scientists take a six-week "snapshot" of California’s air pollution, they bring planes, a large ship and instrument-equipped towers, some as tall as 1,500 feet.

That was the case with CalNex, the largest single atmospheric research endeavor in California history. The effort partnered a team of scientists from UCLA and other UC campuses, the California Air Resources Board, the National Oceanic and Atmospheric Administration (NOAA) and other research teams throughout the country. "It approaches the largest field study that we’ve been involved in," said David Parrish, a lead NOAA scientist for CalNex.

The data, collected over May and June of last year, will help guide policymakers in their decisions about air pollution.


As part of this intensive effort to catalogue air pollution, a UCLA team, led by Jochen Stutz, an associate professor in the Department of Atmospheric and Oceanic Sciences, put up two towers about 30 feet high with about 70 different monitoring devices used by 40 independent teams.

Located on Caltech’s Pasadena campus, the towers were co-managed by Stutz, Caltech and NOAA.

"No group has the capability to measure all these parameters," said Stutz. "So the only way we can really do cutting-edge science is by getting together — everybody specializing in a certain type of measurement — and then combining all our efforts into these huge data sets."

The idea behind the project was to create a massive database of the state’s air within a set period of time — Stutz took measurements from May 15 to June 15 — to focus on air pollution in the most polluted regions. Four of the top five spots on the American Lung Association’s list of the nation’s most polluted cities last year were in California.

For those who live in Los Angeles, Bakersfield and Fresno, among others on the list, air pollution means high levels of emphysema, asthma and cancer. CalNex was an opportunity for the best atmospheric minds in the country to work together, further their understanding of the skies and offer solutions to policymakers desperately in need of guidance.

Just over the Tehachapi Mountains in the agricultural Central Valley near Bakersfield, another tower was being managed by a UC Berkeley team led by Allen Goldstein and Ron Cohen.

Both the UCLA and UC Berkeley towers were equipped with some of the newest and most sensitive sampling equipment in the world, as were the Sutro Tower in San Francisco and another dizzying 1,500-foot-tall steel tower just south of Sacramento. Many of those devices were carefully sniffing out organic chemicals, which are largely responsible for forming ozone and aerosols, the main components of smog causing the health effects associated with air pollution.

"When people study the health effects of these pollutants, these aerosols — or ‘particulate matter’ as the EPA calls them — are the ones that kill the most people by far," said Jose-Luis Jimenez, a University of Colorado researcher also involved with the UCLA tower.

Aerosols largely are chemicals that arise from the reaction in the atmosphere of other compounds either released from human activities or from plants. The reactions of these chemicals pose one of the most mysterious and important questions in atmospheric science today. Unlike carbon dioxide, which lasts for decades and has a relatively simple impact on climate, aerosols come in a dizzying array, last for about a week and may either warm or cool their surroundings.

Making things even more complicated, the air is not stagnant. So the haze around Los Angeles, for example, has changed and reacted so many times that it is hard to say where it all started, scientists said.

Stutz and Goldstein say it is crucial to find the place where the emissions originate and discern how they transform in the atmosphere to create a picture of how the air pollution forms and how to mitigate it. So the towers were placed in key locations where gases from plants are mixing with those from industry or transportation to form smog.

In addition to the highly sensitive and precise sniffers attached to the towers, CalNex used four planes and a large 270-foot ship, the Atlantis, to create a dynamic image of how pollution moves over land and water. The planes flew day and night as high as an airliner and as low as a crop duster to try and capture the complex dynamics of mixing and reacting air.

Meanwhile, Atlantis trolled about along the coast, through San Francisco Bay and up the Sacramento River Delta to collect some of the most accurate measurements ever taken of California’s offshore and inland pollution.

Data sets on this scale give scientists a comprehensive look at the state’s air at one moment in time — a kind of library that future scientists will be able to look at from hundreds of angles undreamed of by the original teams.

"My guess is that we have thought of maybe half the things we are going to be doing with the data. As we learn from the data, we will discover more that we should investigate," Goldstein said.

Scientists with the CalNex project gathered last May, one year after the data were collected, to present and discuss their findings at a California Air Resource Board workshop. "The analysis and the interpretation of such a complex data set take quite awhile," Stutz explained. The researchers are now working on the interpretation of the data and on writing papers on their results.

All the results will be merged together onto one timeline so that any scientist can immediately see all the sites simultaneously. All of this data will result in a series of official papers as early as mid-2012 aimed at informing policymakers. Others will simply focus on basic science questions.

"I really do think that we’re going to write a paper that says, ‘If you want to make the San Joaquin Valley cleaner, here are your choices.’ That honestly is what I am excited about," said Cohen.