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Winter storms in North Atlantic follow the solar cycle.

Winter storms in North Atlantic follow the solar cycle

A tiny, 11-year cycle in the sun's radiation appears to exert a strong influence on the paths of winter storms in the North Atlantic near Great Britain, reports an atmospheric scientist from the National Science Foundation. This finding, to be announced in the May GEOPHYSICAL RESEARCH LETTERS, exemplifies a renewed interest in seeking links between the solar cycle and earthly weather -- a field that has traditionally engendered skepticism and even scorn.

Atmospheric scientist Brian A. Tinsley reexamined a ten-year-old statistical analysis of the relationship between storm tracks in the North Atlantic and the solar cycle. This earlier study found that during a maximum in the solar cycle -- when the total solar output of energy is highest -- the average storm track was 2.5 [deg.] south of the average tracks during a sunspot minimum. However, according to Tinsley's new analysis, the storm tracks during maximum and minimum differ on average by over 6 [deg.], or over 400 miles.

"In fact, this is a very strong pattern," says Tinsley.

For his reanalysis, Tinsley borrowed a concept recently developed by Karin Labitzke of the Free University in Berlin along with Harry van Loon of the National Center for Atmospheric Research in Boulder Colo. (SN: 12/19 & 26/87, p.388). These researchers found last year that stratospheric winds over the tropics seem to be an important element in the relationship between the solar cycle and weather.

These tropical winds reverse their direction in a 26-month cycle called the Quasi-biennial Oscillation (QBO). Labitzke and van Loon found that when they looked only at years from the west phase of the QBO, a strong correlation emerged between the solar cycle and atmospheric temperatures and pressures. Years from the east phase of the QBO showed a similar but less pronounced pattern.

Tinsley extended this method to the record of storm tracks. He found a strong link between the solar cycle and average storm latitude during years of westerly winds, but none during the opposite years.

Most scientists historically have dismissed associations between earth's weather and the solar cycle -- a term which also describes a waxing and waning in the number of sunspots and the emissions of ultraviolet rays and x-rays. "There have been good grounds for skepticism," says Tinsley. "But I do think that good papers have been neglected because of the presence of sloppy ones." The work by Labitzke and van Loon revitalized the field, he says.

A number of researchers are now starting to reexamine meteorological records with this new method of grouping years according to the QBO, although most scientists continue to reserve judgment on the meanings of these statistical correlations. No one has been able to explain how large processes on the earth can respond to small energy changes in the solar output. "It's like the flea on the tail of the dog, wagging the dog," says climatologist Eugene Rasmusson of the University of Maryland in College Park.

Lacking a physical mechanism to link the solar cycle to weather, scientists like Tinsley must rely on statistics to make the association. But the record for the QBO only goes back to 1952, which encompasses only 3-1/2 rounds of the solar cycle -- a relatively small number in statistics. Scientists will be watching the QBO and the weather trends closely as the solar cycle again builds to a maximum expected sometime in late 1989 or 1990.
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Author:Monastersky, Richard
Publication:Science News
Date:May 14, 1988
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