What Causes Prevailing Winds? 1

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What Causes Prevailing Winds?From a light breeze rustling the leaves on the trees in your neighborhood to the powerful winds that drive ocean currents, there’s always wind blowing somewhere. Wind can blow at different strengths and in different directions—but how does wind start blowing in the first place?

Wind is caused by differences in temperature between air in one place and air in another. As warm air in one place rises, cooler air rushes in to take its place—and other air takes the place of that air, and so on. All that moving air is wind.

These trees are bent over because they are in the path of the prevailing winds, which always blow in the same direction. Over time, wind has caused the trees to grow in a bent shape.

In some places on Earth, wind patterns are consistent; we call wind patterns like these prevailing winds. Prevailing winds push ocean currents all over the planet. These winds are consistent because the temperature differences that cause them are consistent. That’s because the temperature differences result from the way light from the sun hits Earth at different latitudes. Latitude is the distance of a location from the equator, either to the south or to the north.

Areas near the equator get more direct sunlight than areas closer to the poles, so air tends to be warmer in areas near the equator. Areas closer to the poles get less direct sunlight, so air tends to be cooler in those places. These differences in air temperature cause wind. Warm air rises, so the warm air near the equator rises and cooler air from near the poles moves in along Earth’s surface to take the place of the rising air. Because the temperature difference between

2 What Causes Prevailing Winds?

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the equator and the poles doesn’t change very much, the winds it causes blow consistently.

Not all winds are prevailing winds, caused by temperature differences between the equator and Earth’s poles. Many of the winds you experience are local winds, which usually aren’t as powerful and don’t travel as far. Local winds can also blow in less consistent patterns than prevailing winds. However, even local winds are caused by the rising of warm air and the motion of cooler air to fill in those spaces. Every breeze you feel is caused by a difference in temperature somewhere.

Major Ocean Currents and Prevailing Winds

The prevailing winds consistently blow in the same patterns. The winds near the equator blow to the west, while the winds farther from the equator blow to the east.