Page 131 - Science Course 1 (Book 2)

Mo9-L5a: What are Air Currents? Mo9-L5a: What are Air Currents?

Key Concept

What are Air Currents?

How does uneven heating of Earth’s surface result
in air movement?

Global Wind Belts

Polar easterlies
Three cells in each hemisphere move air through the atmosphere.

In the f rst cell, hot air at the equator moves to the top of the
troposphere then moves toward the poles until it cools and
moves back to Earth’s surface near the 30° latitude.
Westerlies
The second cell, between 30° and 60° latitude, is not a
convection cell because its motion is driven by the
other two cells. Trade winds

The third cell, at the highest latitudes, is also a
convection cell. Air from the poles moves toward the Trade winds
equator along Earth’s surface, and warmer air is pushed
upward by the cooler air near the 60° latitude.
Westerlies
The three cells exist in both the Northern and Southern
Hemispheres.

Most of the air in this convection cell returns to the equator near
Earth’s surface. Polar easterlies

The Coriolis effect occurs when the rotation of Earth
causes moving air and water to move to the right in
the Northern Hemisphere and to the left in the South-
ern Hemisphere.

The contrast between high and low pressure and the
Coriolis effect creates distinct wind patterns, called
prevailing winds.

Path of wind without Coriolis effect

Approximate path of wind

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