Scientists, ships, aircraft to profile Asian pollution and dust

March 19, 2001

UCAR to Direct Operations for NSF

NCAR to Guide Aircraft, Enhance Climate Models, Untangle Mysteries of Atmospheric Mercury

BOULDER--The densest yellow dust storms in recent times blew into Beijing and elsewhere from over the high deserts of China and Mongolia last spring. This year's plumes have again begun their eastward journey toward heavily populated Asian cities and the northwest Pacific Ocean. Awaiting their arrival will be 130 scientists from nine countries, along with two research vessels, four research aircraft, a half dozen satellites, and extensive ground- based networks of lidar, radar, and other instruments. The researchers are gathering in the western Pacific region to observe the optical, chemical, and radiative properties of this year's plumes as they collide with some of the planet's heaviest pollution.

The Aerosol Characterization Experiment (ACE-Asia) extends from late March through mid-May. (Aerosols are fine particles suspended in air.) Researchers will be tracking and observing sulfate and carbon- containing aerosols emitted by soft coal combustion and the burning of wood and field growth. Sea salt adds slightly to the region's aerosol load. And then there's the dust.

The developing Asian countries "have got a unique fuel mix, but the dust is what makes it really interesting," says Barry Huebert (University of Hawaii), principal investigator for ACE-Asia and two earlier ACE experiments.

Timing is important. The dust storms occur in winter over the high deserts, sending dense plumes over the populous cities of China, Japan, and Korea in spring. By summer, thunderstorms change the circulation, disrupting the large dust plumes, and "rain out" much of the pollution.

The field operations director for ACE-Asia is Richard Dirks of the University Corporation for Atmospheric Research (UCAR), who will oversee daily operations, logistics, and data analysis for the National Science Foundation from project headquarters in Iwakune, Japan. "The science is essential to understanding how human activities are affecting the global climate," says Dirks. "The experiment is also groundbreaking in its collaboration among countries that have not worked together in the past and historically have been cautious about sharing data."

The National Center for Atmospheric Research

Scientists from the National Center for Atmospheric Research (NCAR) will forecast the pollution's pathways, guiding research aircraft toward the densest plumes. Using a technique developed in a recent aerosol experiment over the Indian Ocean, NCAR's William Collins and Philip Rasch will combine weather information provided by the National Centers for Environmental Prediction with a chemical transport model to produce two-day aerosol forecasts. The forecast model is a prototype for an important next step: assimilating aerosol data into global climate models in a way that allows researchers to experimentally move the aerosols around the globe and estimate their vertical profiles. "The lifetime of aerosols and their long-range transport increases dramatically, high up in the atmosphere," says Collins. "If we can get that kind of vertical definition and mobility in the climate models, it would be a big step toward understanding aerosol impacts on climate."

The observations will provide ground truth for global climate models on how these multicomponent aerosols affect clouds, solar radiation, and ultimately the earth's energy balance and global climate. The impact of aerosols and clouds on climate has eluded modelers' best efforts, partly because of a lack of data. Desert dust complicates the problem because it can both cool the earth by scattering sunlight back to space and also warm it by absorbing solar and infrared radiation.

Among the research aircraft will be a C-130, owned by the National Science Foundation and operated by NCAR, on its first research mission since acquiring four brand new engines and a sporty paint job. Its newly developed intake inlets can for the first time accurately capture air containing both large and fine particles in their natural distributions, undisturbed by instrument turbulence.

Using a highly precise chemical sensor aboard the C-130, NCAR's Hans Friedli and Lawrence Radke will try to untangle some of the mysteries of mercury, an elusive and toxic metal that damages or destroys nerve tissue and kills flora and fauna. Mercury has recently been targeted by President Bush as one of three atmospheric pollutants for study and possible abatement. Friedli and Radke recently discovered that forest fires and other biomass incineration are an important source of mercury. During ACE-Asia, they will search for the origins of long-lived atmospheric mercury species, track their journeys through the troposphere, and study how these compounds leave the atmosphere and become dangerously concentrated within the food chain.

"We believe the mercury-smoke connection will change how we think of mercury in the atmosphere," says Radke, who is also a wildfire expert. Radke and Friedli will focus on gaseous mercury produced by industrial sources in Asia.

NCAR chemist Teresa Campos will measure the atmospheric trace gases carbon dioxide, carbon monoxide, and ozone. The three "identifiers" will give scientists clues to the age and history of the various air masses. "We're also suspecting that carbon monoxide and mercury emissions are going to correlate pretty well," she says.

ACE-Asia is the third in the ACE series of experiments, each one ramping up the targeted pollution levels, so that this year's project will be measuring the heaviest aerosol pollution on the planet. The first ACE was based in Tasmania to measure a pristine environment, the second in the Canary Islands to observe pollution from Europe as it merged with Saharan dust.
NCAR is managed by the University Corporation for Atmospheric Research, a consortium of more than 65 universities offering Ph.D.s in atmospheric and related sciences.

On the Web:

Note to Editors: A press briefing on ACE-Asia will take place at
10:00 a.m. EST on Tuesday morning, March 20, in Room 6013, Department
of Commerce Building, 14th Street and Constitution Ave. NW,
Washington, D.C.

National Center for Atmospheric Research/University Corporation for Atmospheric Research

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