From years of watching TV weather I know that our weather (in particular the jet stream) moves from west to east. Yet, as the sunrise and sunset show, the earth rotates in that same direction. Does that mean that the atmosphere is rotating around the planet faster than the planet itself is spinning? Shouldn’t it be just the opposite? –Charles Barksdale, Baltimore
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It would be if the world were run by newspaper Q&A columnists. You try explaining convection currents and the Coriolis effect in 600 words or less. Fact is, though, there’s no reason to expect the winds and weather to move slower than the planet. Ignoring all other considerations, friction alone would keep the atmosphere spinning at the same rate as the earth beneath it. So why do the jet stream and weather in general move faster than the earth? First the simplified explanation. Convection currents in the temperate latitudes tend to push the surface winds north. The rotation of the earth tends to push anything northbound toward the east. Why? Because things near the equator are moving east faster than things near the pole. At the equator you’re rocketing east at 1,000 miles an hour due to the earth’s rotation. At the North Pole everything is pretty much stationary. As you fly north from equator to pole, therefore, you find you’re moving east faster than the earth beneath you. Same with the winds–they’re deflected east. This is called the Coriolis effect.
You don’t get it, I know. The English language is a pathetic vehicle for this sort of thing. Perhaps Slug’s drawing will make matters a little clearer. If not, take heart: I could have dragged in conservation of angular momentum, but didn’t. There are some things mere mortals just don’t need to know.
Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.
