Extreme weather conditions linked to wind pattern variations

Variations in the flow of high altitude winds that normally blow from west to east around the planet can have a major influence on prolonged bouts of unseasonal weather - whether it be hot, cold, wet or dry - in parts of Europe, Asia and the US, said a study.

Changes in air flow patterns around the northern hemisphere impact weather conditions in several parts of the world, the findings showed.

"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," said James Screen, a mathematics research fellow at University of Exeter in Britain.

The high altitude winds do not follow a straight path. The flow meanders to the north and south, in a wave-like path.

These wave patterns are responsible for sucking either warm air from the tropics, or cold air from the Arctic, to Europe, Asia, or the US. They can also influence rainfall by steering rain-laden storms.

The study showed that larger waves can lead to droughts in central North America, Europe and Central Asia, while Western Asia may experience prolonged wet spells.

Western North America and Central Asia are more prone to heat waves, while eastern North America is more likely to experience prolonged outbreaks of cold.

The study used detailed land-based climate observations to identify episodes of abnormal temperature and rainfall from 1979-2012 and then examined the wave patterns during these events.

"The findings are very important for decision makers in assessing the risk of, and planning for the impacts of, extreme weather events in the future," said Ian Simmonds, professor from University of Melbourne in Australia.