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August 29, 2009

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Solar output may be key to storm cycles

SMALL changes in the energy output of the sun can have a major impact on global weather patterns, such as the intensity of the Indian monsoon, that could be predicted years in advance, a team of scientists has found.

The sun swings through an 11-year cycle measured in the number of sun spots on the surface that emit bursts of energy.

The difference in energy is only about 0.1 percent between a solar maximum and minimum, and determining just how that small variation affects the world's climate has been one of the great challenges facing meteorologists.

Using a century of weather observations and complex computer models, the international team of scientists led by the National Center for Atmospheric Research in the United States showed that even a small increase in the sun's energy can intensify wind and rainfall patterns.

"Small changes in the sun's output over the 11-year solar cycle have long been known to have impacts on the global climate system," said Julie Arblaster, from the Center for Australian Weather and Climate Research, a co-author of the study published in the latest issue of the journal Science.

The researchers found that during periods of strong solar activity, the air in the upper atmosphere heats up.

The extra warming alters wind patterns in the upper atmosphere, which in turn increases tropical rainfall.

Increased sunlight at solar maximum also causes a slight warming of ocean surface waters across the subtropical Pacific, where clouds are normally scarce, according to the study.

The Indian monsoon and many other regional climate patterns are largely driven by rising and sinking air in the tropics and subtropics.

Solar-cycle predictions could help meteorologists estimate how those circulation patterns, changes in sea surface temperatures and regional weather patterns might vary.



 

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