How does wind happen?

Hurricane Katrina. Courtesy of NOAA

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This is an excellent question, and one that I was curious about myself when I was younger. I would often ask my parents scientific questions, and they would do their best to respond, sometimes without actually knowing the correct answer. When I asked this same question, my parents told me something along the lines of “wind is caused by the rotation of the Earth.” While the Earth’s rotation does play a significant role in wind and weather patterns, this is not the complete answer.

You may have heard that hot air rises and cool air sinks. This is because air expands as it is heated, so it is less dense than cool air. This is an important phenomenon because the sun does not heat the surface of the Earth equally — air near the equator is significantly hotter than air near the poles, for example. Heated air expands, rises, and creates an area of low pressure, as explained by National Geographic. Conversely, cold air contracts, sinks, and creates areas of high pressure. Air will flow from areas of high to low pressure, causing wind. The greater the difference in pressure, the faster the air will flow, and the stronger the wind will be. 

”Properties of Matter Reading Selection: Density Creates Currents.” [Online]. Available:

The rotation of the Earth does affect the wind, but it does not cause it. If the Earth were stationary, air would flow directly from areas of high to low pressure. As it so happens, the Earth is not stationary — it rotates around its axis. Earth’s rotation means that wind that would normally follow a straight path is deflected: clockwise in the northern hemisphere and counterclockwise in the southern. This creates what’s called the Coriolis effect. This complicated phenomenon is the cause of many weather patterns, including hurricanes and tornadoes.

This article was edited by Emi Krishnamurthy and Ashley Schefler.

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