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12: Climate
12.3: Effect of Atmospheric Circulation on Climate

12.3: Effect of Atmospheric Circulation on Climate

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Would you like to go to the horse latitudes?

Imagine you're on a sailing ship that's carrying horses among other cargo. You want to go from Spain to northern South America. For a smooth ride west, you need to get the ship into the trade winds. But where the trade winds and the westerlies meet is a zone where air flows vertically downward. It's hard to get through there in a sailing ship. So your ship gets stuck. For weeks. There's no more water or food for the horses so you throw them overboard. Some people think this is where the horse latitudes got their name.

More Effects of Latitude on Climate

We saw that the amount of solar radiation an area receives depends on its latitude. The amount of solar radiation affects the temperature of a region. Latitude has other effects on climate.

Latitude and Prevailing Winds

Global air currents cause global winds. The figure below shows the direction that these winds blow (Figure below). Global winds are the prevailing, or usual, winds at a given latitude. The winds move air masses, which causes weather.

The direction of prevailing winds determines which type of air mass usually moves over an area. For example, a west wind might bring warm moist air from over an ocean. An east wind might bring cold dry air from over a mountain range. Which wind prevails has a big effect on the climate. What if the prevailing winds are westerlies? The westerlies blow from nearer the Equator to farther from the Equator. How would they affect the climate?

Map of atmospheric circulation cells

The usual direction of the wind where you live depends on your latitude. This determines where you are in the global wind belts.

Latitude and Precipitation

Global air currents affect precipitation. How they affect it varies with latitude (Figure below). Where air rises, it cools and there is precipitation. Where air sinks, it warms and causes evaporation. These patterns are part of the global wind belts.

Map of global air currents and climate

Global air currents are shown on the left. You can see how they affect climate on the right.

"Five Factors that Affect Climate" takes a very thorough look at what creates the climate zones. The climate of a region allows certain plants to grow, creating an ecological biome.

Summary

Prevailing winds are the result of atmospheric circulation cells. They influence the climate of a region.
Rising and sinking air can influence the precipitation of a region.
Atmospheric circulation cells create the general climate of a region.

Review

What are prevailing winds? How do they affect climate?
Where is there not much wind?
How do atmospheric circulation cells affect precipitation?