China dust going north this year
By Jan TenBruggencate
Advertiser Staff Writer
Less China dust than usual is falling on Hawai'i this season, apparently because the annual dust cloud is following a more northerly path across the Pacific.
"We usually see these events in April and May," said John Barnes, director of the Mauna Loa Observatory, the research station near the top of Mauna Loa, where scientists measure such things as atmospheric carbon dioxide, and the density and origin of dust in the higher elevations.
Barnes said the winds pick up in the springtime on the high plateaus of China, and dust particles are shipped into the upper atmosphere and carried eastward across the Pacific. As the clouds blow over populated areas, they pick up pollutants like sulfur compounds from China's coal-fired power plants and chemicals from Asia's other industrial polluters.
Much of the dust drops out over the Pacific, and if the cloud passes over the Islands, it is added to the soil here. Archaeologists have been able to detect the presence of Asian particles in older Hawaiian soils, suggesting this has been going on for millenniums.
This year, the Asian dust cloud took a route that brought it by Alaska, and then over parts of Canada and the Mainland. Researchers say it started as a sandstorm on Mongolia's Gobi Desert and China's Taklimakan Desert, and was kicked as high as seven miles up as it moved on a path that took it over the Gulf of Alaska on its way to Canada and the contiguous United States.
The cloud has a familiar look to Russ Schnell, formerly head of the Mauna Loa Observatory and now director of observatory operations at the National Oceanic and Atmospheric Administration in Boulder, Colo. He saw it over Hawai'i when he worked here, and now he's using it to make a point about industrial pollution in Asia.
"People are finally realizing that what they have been saying for years is true. Pollution from Asia is being carried across the oceans," Schnell said in an interview with the Environmental News Network.
What is shocking people is just how much there is.
A region from Calgary, Canada, to Phoenix, Ariz., is covered by a visible haze. The cloud covers a quarter of the United States. Particulate matter in the air has increased fourfold in some areas and is approaching federal air pollution limits.
When the annual cloud takes its normal southerly course, it has farther to go and can dissipate after passing through Hawai'i. It often does not reach the Mainland, Barnes said, so researchers there seldom see it.
It is not clear what causes the changes in the direction of the cloud.
"We saw the same thing in 1998 during that big El Nino. But we don't have a reason for this year," which is a fading La Ni–a year, he said.
Jan TenBruggencate is The Advertiser's Kaua'i bureau chief and its science and environment writer. Call him at (808) 245-3074 or e-mail jant@honoluluadvertiser.com.
