Researchers found that variations in wind patterns affect parts of Europe, Asia and the U.S. by causing drawn out periods of unusual weather conditions.
The winds, which blow from west to east at high altitudes, travel in wave-like patterns through the north and south rather than straight across. These patterns bring heat to western North American and central Asia, and unusual cold spells to eastern North America. They also bring higher chances of prolonged droughts and torrential rainstorms to certain locations.
The findings were published in Nature Climate Change by researchers from the University of Exeter and the University of Melbourne. The lead author of the paper, Dr. James Screen of University of Exeter, explains that the effects of the variable wind patterns differ according to the geographic location.
"The impacts of large and slow moving atmospheric waves are different in different places. In some places amplified waves increase the chance of unusually hot conditions, and in others the risk of cold, wet or dry conditions," says Screen in a statement released on Sunday, June 22.
Using climate observations, including records of unusual and extreme temperatures and rainfall, conducted from 1979 to 2012, Screen and co-author Ian Simmonds of the University of Melbourne compared their observations with the wave patterns during the period. They found that extreme weather conditions were often accompanied by highly amplified waves, and mild weather conditions were accompanied by "attenuated," lower amplitude waves.
In addition to the extreme temperatures, the wind patterns are often harbingers of dry spells and wet spells. The large wave wind patterns may be responsible for the droughts seen in central North America, Europe and central Asia. These waves also seem to cast off heavy rain seasons into western Asia.
While Simmonds and Screen do not claim that these wind patterns are the direct causes of the extreme weather conditions, their analysis show a statistically significant association between the trends, meaning that the amplified waves increase the probabilities of the extreme conditions. Whether or not this is a proven cause-and-effect relationship remains to be seen.
Still, the significance of the data is clear and offers strong, noteworthy evidence. As the authors explain in the paper, "a better understanding of the role of planetary waves in causing mid-latitude weather extremes is essential for assessing the potential environmental and socio-economic impacts of future planetary wave changes."
