Dear Tom,

Why do wind speeds increase with increasing height above the ground?

Jaslin Malkov, Chicago

Dear Jaslin,

You are correct. Wind speed generally increases as one ascends into the atmosphere. Wind speeds are lowest at ground level and get higher one foot above the ground, higher still a few feet above the ground, and higher still as one goes above that. Under standard conditions, wind speeds often increase up to the top of the troposphere, which is located from about four miles aloft at Earth’s poles, to eleven miles at the Equator.

Friction with Earth’s surface and ground-based objects accounts for the increase in wind speed below an altitude of about 2,000 FT (a layer referred to as the Planetary Boundary Layer). Air moving across terrain and ground-based obstructions results in a drag on air flow causing winds to slow down accordingly

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