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Jet Stream Geography
Mon Jan 27, 2003
Listen in RealAudio 
Hi, I'm Bryan Yeaton for the Mount Washington Observatory and this is The Weather Notebook.
Today on the show we talk about the jet stream, a fast-moving river of air that circles the
globe around eight miles above the earth.
The whole atmosphere is a bit like a river of air that circles around the planet from west to
east; the jet stream is just the fastest part of this river. Most folks are surprised to find
out that the average speed of the Jet Stream is only about 80 miles per hour. However, jet
streaks -- concentrated areas of the Jet Stream -- can surpass 200 miles per hour.
In the winter, there is usually a tropical Jet and a polar Jet, but the polar Jet fades away
in the summer.
The jet stream indicates the general movement of the atmosphere, sometimes straight west to
east, sometimes oscillating up and down like a roller coaster. The more it curves, the more
weather you have, and what causes the curves is, in part, explained by geography.
For over a billion years the continents have been floating around the planet like bumper cars.
The present configuration has two big land masses and two big oceans in the Northern
Hemisphere, with little land masses and a whole lot of ocean south of the equator. The large
difference between the temperatures of land and water, especially in the winter, spring and
fall, causes pressure changes in the atmosphere above, and helps the Jet Stream snake its way
across the middle part of North America and the rest of Northern Hemisphere.
The Weather Notebook is made possible by a grant from The National Science Foundation.
Additional support comes from Subaru of America. Got a story idea? Give us a call at 888
RAIN-001. Thanks today to the entire Weather Notebook staff, Doug Sanborn, Melody Nester,
Sean Doucette and Peter Crane.
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