Feb 20, 2015

The Siberian snow connection

Carolyn Gramling
  • Reviews Judah Cohen's theory on the connection between Arctic change and midlatitude weather
  • Cohen envisions a series of causal links from Siberian snow via the lower atmosphere to large-amplitude planetary waves that reach into the stratosphere and shape weather patterns in the midlatitudes
  • Outlines Cohen's “six-step” cycle: (1) with broader snow cover blanketing more of Siberia in October, there is more cold, dense air in the lower atmosphere; (2) the high-pressure center known as the Siberian high becomes bigger and stronger; (3) by November to December, these atmospheric transformations increase the flow of energy upward, from the troposphere into the stratosphere; (4) the stratosphere suddenly warms, and (5) the stratospheric polar vortex—the mass of cold air that is normally confined to the Arctic—breaks down, (6) creating a more meandering jet stream and allowing cold polar air to penetrate farther south