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Name: Jim
Status: educator
Grade: 12+
Location: AK
Country: USA
Date: Winter 2012


Question:
I teach Earth Science from a book called "Visualizing Earth Science" by Zeeya Merali and Brian Skinner. They explain global wind patterns and show a Polar Cell creating a high pressure pattern over the poles (I will speak only about the North Pole now as I live in Alaska and that is our weather driver.

It then goes on to explain Rosby Waves and how they spin off or "spawn" (my word) cold low pressure systems from off of the poles. How does a high pressure system (at the pole) spin off a low pressure system?


Replies:
Jim

First of all, you cannot ignore the peeling effect at the boundaries of the High and Low pressure zones where pieces of the High pressure area just peel off. And High pressure air tends toward lower pressure zones in an attempt to equalize the pressures.

Second is the coriolis effect ( http://en.wikipedia.org/wiki/Coriolis_effect) This is an effect from the rotation of the Earth.

Sincere regards, Mike Stewart


Jim,

Rossby waves are meanderings in the polar jet stream. There are usually 3 to 4 large ones circling the Arctic in a westward direction. However, the mean wind direction in the polar jet is from west to east, so if a Rossby wave becomes large and perturbed, it can be sheared off by the eastward moving polar jet and move southwards, thereby becoming a cold low pressure system.

David R. Cook Meteorologist Climate Research Section Environmental Science Division Argonne National Laboratory


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