GMAO / GSFC / NASA / SCIENCE PHOTO LIBRARY GMAO / GSFC / NASA / SCIENCE PHOTO LIBRARY
Satellite imagery of the disruption of the polar vortex in the northern hemisphere winter 2012-2013. The data show a major stratospheric sudden warming (SSW) event, linked to the distortion and reversal of the normal westerly (moving west to east) flow of air. The large vortex (white) over the North Atlantic Ocean at the start of the clip breaks up into several smaller vortices. This is due to air from lower latitudes (dark) becoming entrained in the polar flow, forming an anti-cyclonic region (dark, rotating clockwise) over Japan and eastern Russia, which disrupts the flow across the region. Although dramatic, such events are not rare, occurring every two years on average. They can cause winds to reverse near the surface too, leading to very cold spells, especially in North America and Europe. The brightness indicates the potential vorticity of the air, a measure of its rotation within its flow, at an altitude of 35 kilometres. Brighter regions have more vorticity. A major SSW occurs when the temperatures in the stratosphere around the pole increases by at least 25 Kelvin within a week, causing the wind to change direction. The data were gathered by the GEOS-5 satellite every hour between 15th December 2012 and 28th January 2013.
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