Tag: Arctic oscillation

Geography In the News

Oscillations of a Chilly Variety

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NorthHemLSTanom_TMO_200912.jpg

I returned from a trip to Boston this weekend to find much warmer temperatures in the nation’s capital. Although I did not venture outside the office midday, Weather.com tells me today’s high was in the mid-50s. Many around me are welcoming the shift to milder weather; I must admit I enjoyed the cold snap, and particularly the great Mid-Atlantic blizzard that blanketed the city in over a foot of snow just before the holiday “recess.” Of course, I’m not a farmer dependent on seasonable conditions to sustain crop yields–and even I missed the fresh produce that succumbed to the frost when I visited the local market last month.

Why did the entire Eastern U.S. and much of Eurasia experience such a chilly several weeks? You may or may not have heard buzz about the Arctic Oscillation, a climatic phenomenon not unlike El Niño/La Niña. The main difference: The Arctic Oscillation (AO) is a north-south shift in pressure and temperature in the atmosphere and ocean, while El Niño/La Niña is an east-west shift in pressure and temperature. Well, at a basic level.

Check out this thematic map, which compares December 2009 surface temperatures with December 2000-2008 averages around the globe.

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