March 25, 2011

World’s Oceans Are Windier, Rougher

An increase in average wind speeds blowing over the world's oceans over the past quarter-century have generated higher waves and rougher seas, and researchers said those increased wind speeds could lead to more water vapor in the air, providing added moisture for rain and potentially increasing rainfall.

In a study published online in the journal Science on Thursday, researchers led by Ian Young of Swinburne University of Technology in Australia said the increased wind speed averages could compound any increase from global warming. They added that over a 23-year period, average wind speed over the oceans rose by 0.25 percent per year.

The researchers noted that the proportion of increase in wave height was less than for wind speed, while the increase for extreme winds was more than for average winds. They said that higher winds are not necessarily the result of global warming.

However, Eugene S. Takle, director of the climate science program at Iowa State University, noted that higher wind speeds causes more evaporation to rise, resulting in more moisture in the air even without global warming. And warming shown in many studies would also increase evaporation.

Takle, who was not involved in Young's research, published a study with colleagues two years ago closely following the same theme. However, in their study, they recorded wind speeds over land. The wind speeds showed a decrease, rather than an increase that Young's team found in measurements from satellites and buoys.

Young and colleagues studied satellite records from 1985 to 2010. Their research lacked data from 1990-91 because of satellite problems.

"I don't think these results provide a clear contradiction to our findings of declining wind speeds over land, since measurements are made in different environments," Takle told The Associated Press.

Day-to-night temperature changes are different over land than over oceans, and the boundary layer -- the portion of the atmosphere that most closely interacts with the surface -- is normally thicker over land than water, Takle explained.


On the Net: