China dust cloud circled globe in 13 days

HONG KONG Mon Jul 20, 2009 1:09pm EDT

People ride amid sandstorms in Turpan, Xinjiang Uygur Autonomous Region May 26, 2009. REUTERS/China Daily

People ride amid sandstorms in Turpan, Xinjiang Uygur Autonomous Region May 26, 2009.

Credit: Reuters/China Daily

HONG KONG (Reuters) - Dust clouds generated by a huge dust storm in China's Taklimakan desert in 2007 made more than one full circle around the globe in just 13 days, a Japanese study using a NASA satellite has found.

When the cloud reached the Pacific Ocean the second time, it descended and deposited some of its dust into the sea, showing how a natural phenomenon can impact the environment far away.

"Asian dust is usually deposited near the Yellow Sea, around the Japan area, while Sahara dust ends up around the Atlantic Ocean and coast of Africa," said Itsushi Uno of Kyushu University's Research Institute for Applied Mechanics.

"But this study shows that China dust can be deposited into the (Pacific Ocean)," he told Reuters by telephone. "Dust clouds contain 5 percent iron, that is important for the ocean."

In a paper published in Nature Geoscience, scientists described how they used a NASA satellite and mathematical modeling to track and measure the movement of the dust cloud, which formed after the dust storm on May 8-9 in 2007.

The desert is in the Chinese northwestern region of Xinjiang.

The researchers, led by Uno, found that the dust clouds were lifted 8-10 km (5-6 miles) above the earth's surface, and transported more than one full circle around the earth.

"The most important achievement is that we tracked this through one full circuit round the globe, nobody has done this before. After half a circuit, usually the dust concentration gets very low and you can't track it," Uno told Reuters.

"This means that dust concentration, dust lifetime is very long, more than two weeks."

The dust cloud measured about 3 km (1.9 miles) vertically and up to 2,000 km horizontally and it stayed that way even after one full trip around the globe.

"The reason why the cloud structure was very well maintained was because the dust was uplifted ... where the atmosphere is very stable," Uno said.

Researchers believe dust particles trigger the formation of high-altitude cirrus clouds -- although experts have no idea whether such clouds warm or cool the earth.

(Reporting by Tan Ee Lyn; Editing by Sugita Katyal)

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