Tue 26 Mar 2013
What the planet can expect in the future and humans should be prepared for. A pulse starts some where when it is either cooler or warmer than the rest of the world. This temperature variant then pulses around the world until splat, it strikes a particular area with an unknown effect. Fire here, drought there, and a flood occasionally.
Weather Extremes: Atmospheric Waves And Climate Change
By Vladimir Petoukhov and Stefan Rahmstorf, via The Conversation
The northern hemisphere has experienced a spate of extreme weather in recent times. In 2012 there were destructive heat waves in the U.S. and southern Europe, accompanied by floods in China. This followed a heat wave in the U.S. in 2011 and one in Russia in 2010, coinciding with the unprecedented Pakistan flood — and the list doesn’t stop there.
Now we believe we have detected a common physical cause hidden behind all these individual events: Each time one of these extremes struck, a strong wave train had developed in the atmosphere, circling the globe in mid-latitudes. These so-called planetary waves are well-known and a normal part of atmospheric flow. What is not normal is that the usually moving waves ground to a halt and were greatly amplified during the extreme events.
Looking into the physics behind this, we found it is due to a resonance phenomenon. Under special conditions, the atmosphere can start to resonate like a bell. The wind patterns form a regular wave train, with six, seven or eight peaks and troughs going once around the globe (see graph). This is what we propose in a study published this week together with our colleagues of the Potsdam Institute for Climate Impact Research (PIK).
Normally, an important part of the global air motion in the mid-latitudes of the Earth takes the form of waves wandering around the planet, oscillating irregularly between the tropical and polar regions. So when they swing northward, these waves suck warm air from the tropics to Europe, Russia, or the US; and when they swing southward, they do the same thing with cold air from the Arctic. This is a well-known feature of our planet’s atmospheric circulation system