Switching Phases in the Arctic

(via NOAA Environmental Visualization Laboratory - Switching Phases in the Arctic)

Blasts of cold Arctic air during the 2010 winter froze many parts of Northern Europe, Canada, and the U.S. One of the drivers of those frigid temperatures was very high pressure situated over the Arctic near Greenland. In 2010, the Arctic was in what is called a “negative phase” of the Arctic Oscillation - a climate cycle that affects seasonal weather patterns. This year, conditions have reversed, and the Arctic is now in a “positive phase,” whereby lower pressure sits over that same region. The differences between the surface pressure during November 2010 (left) and 2011 (right) can be seen in this image. Blue indicates areas where the geopotential height at 1000 meters (a proxy for mean sea level pressure) is lower than normal, whereas orange indicates areas with a higher than normal value.Related Information:NCEP Reanalysis Data from NOAA/ESRL/PSDTerms of Use:Please credit NOAA