- The Washington Times - Sunday, January 26, 2003

THIS STUFF BLOWS

Mariah, Passat, tremontana, nor'easter — other names for what we also know as wind, or air in motion relative to Earth's surface.

Authorities say there are three-dimensional properties to wind. That's interesting, but there's enough experience with the horizontal and vertical versions, so maybe we'll skip the up, up, and away.

Our basic question is, where does the wind come from? We found a clue one warm day (remember warm days?) when we opened the freezer door and kept it open a while, in a teenager-like pose trying to decide what to remove for dinner.

All of a sudden, we felt a breeze coming out of the freezer. From the side we could see air frost up and spill out of the freezer door. At the risk of running up the utility bill and having the ice cream melt, we watched a little while longer. This was, in microcosm, wind.

The cold air in the freezer and warm air in the kitchen were engaged in kind of a balancing act. Take the same ingredients on a larger scale — ice at the poles, a few thousand miles of ocean, some drastic temperature variations and Earth's rotation, and there you have it!

About that rotation, it produces what's called the coriolis effect — after French physicist Gaspard Coriolis. It's another part of the engine behind the wind — what get the warm and cold airs colliding to begin with.

The Coriolis effect basically says the angular velocity of an object increases with its closeness to the center of the object. That means if the air at sea level and at the equator is moving at about 10 miles an hour eastward (actually about 1,010 miles an hour when you roll in the planet's rotational velocity), the air at, say, 10,000 feet above sea level will tend to move more slowly with less angular velocity (further away from center.) This slower-faster thing is what jumbles up the air mass that surrounds the Earth. Cool.

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