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What makes the wind?

Courtesy of my toddler: What makes the wind? Now, my gut says the spin of the Earth has something to do with it, but that doesn't explain variations in wind speed, storms, etc. Meteorology is a mystery to me. Whatever the answer is, I just have to try and translate to my toddler.

On a general level, wind isn't that complicated! You're right that it has something to do with the spin of the Earth, but more than that, it has to do with the fact that warm air rises (as you can see because hot air balloons work). When hot air rises, cooler air rushes in to fill the space it leaves, thus making wind at the surface. At height, the air goes from the warmer place to the cooler place. For example, near the coast on a summer day, the air over the land heats up more than the air over the sea, and rises, and the cooler air that comes in to fill the space it leaves is the "sea breeze." A very large example is the monsoon in Southeast Asia. The Tibetan plateau heats up during the summer, air rises, and cooler, moister air from over the ocean rushes in to replace it. When this air is forced to rise to get over the plateau, it dumps rain on the areas below. On a larger scale, the sun heats the earth unevenly - more energy comes in at the equator than at the poles. So the warmer air near the equator rises, and cooler air from poleward comes in to replace it. Well then, why are the prevailing winds more West-East or East-West than North-South or South-North? That's when the spin of the earth comes in. Just like the center of a record spins slower than the edge because it has a shorter path to travel, the earth's equator spins faster than higher latitudes. This means that air that is travelling towards the equator is deflected westward and air that is travelling towards the pole is deflected eastward. This breaks up the wind patterns of the globe into 3 overall "cells" per hemisphere. That is why the winds in the tropics blow mainly east to west, and at mid latitudes, the winds blow mainly west to east. This also controls precipitation patterns on a large scale because air that is rising often loses its moisture as rain. So there you go - some basic meteorology! I hope it answers your question! For your son or daughter - here's a fun website that explains not only where wind comes from but how wind power is produced - it's aimed at elementary school kids, but should help you "translate."

July 2003, Cathy Jordan (more by Cathy Jordan) (Like this Answer)

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