Weather extremes associated with trapping of atmospheric waves

The world has suffered from severe regional weather extremes in recent years, such as the heat wave in the United States in 2011 or the one in Russia 2010 coinciding with the unprecedented Pakistan flood. Behind these devastating individual events there is a common physical cause, according to scientists at the Potsdam Institute for Climate Impact Research (PIK). The study will be published this week in the US Proceedings of the National Academy of Sciences and suggests that man-made climate change repeatedly disturbs the patterns of atmospheric flow around the globe's Northern hemisphere through a subtle resonance mechanism.

An important part of the global air motion in the mid-latitudes of the Earth normally takes the form of waves wandering around the planet, oscillating between the tropical and the Arctic regions. So when they swing up, these waves suck warm air from the tropics to Europe, Russia, or the US, and when they swing down, they do the same thing with cold air from the Arctic,” explains lead author Vladimir Petoukhov.

“What we found is that during several recent extreme weather  events these planetary waves almost freeze in their tracks for  weeks. So instead of bringing in cool air after having brought warm air in before, the heat just stays. In fact, we observe a  strong amplification of the usually weak, slowly moving  component of these waves,” says Petoukhov. Time is critical  here: two or three days of 30 degrees Celsius are no problem, but twenty or more days lead to extreme heat stress. Since many  ecosystems and cities are not adapted to this, prolonged hot  periods can result in a high death toll, forest fires, and  dramatic harvest losses. 

Click here to go to full press release at Potsdam Institute for Climate Research website.