Air Movement

Air Movement

Atmospheric Circulation and GlobalWinds Because more solar energy strikes the equator, the air over the equator is warmer than elsewhere on the planet. Warm air has low density, so it rises and forms a low pressure zone. At the top of the troposphere, half of the warm air moves toward the north pole and half toward the south pole along the top of the troposphere. At about 30 degrees north latitude, the air from the equator meets air flowing toward the equator from higher latitudes and descends to

the ground, creating a high pressure zone.

Multiple Choice

Where cool air descends to the ground there is a

• high-pressure zone

• Foehn wind.

• valley breeze.

• polar front.

Once on the ground, the air returns to the equator. These air movements form a convection cell, called a Hadley cell, which is found between 0 and 30 degrees north latitude. A similar Hadley cell is also found between 0 and 30 degrees south latitude, except the air flows in the opposite directions. In addition to Hadley cells, there are two other major convection cells in each hemisphere. A Ferrell cell is located between 30 and about 60 degrees north or south latitude.

In the Northern Hemisphere, air in this cell moves from north to south; it moves in the opposite direction in the Southern Hemisphere. A polar cell is located between about 60 and 90 degrees north or south latitude. In the Northern Hemisphere, the air in this cell moves from south to north and descends at the north pole. It moves in the opposite direction in the Southern Hemisphere and descends at the

south pole.

Multiple Choice

Winds blow when air flows from areas of higher to lower

• elevation.

• pressure.

• temperature.

• altitude.

Global circulation cells cause global wind belts. Global wind belts are enormous. They occur because of the flowing air at the bottom of the major circulation cells. In both hemispheres, the global wind belts are the trade winds, westerlies, and polar easterlies.

• In the Northern Hemisphere, the trade winds flow from northeast to southwest at the bottom of the Hadley cell; the westerlies blow from southwest to northeast at the bottom of the Ferrell cell; and the polar easterlies blow from northeast to southwest at the bottom of the polar cell.

Multiple Choice

When warm air cools it

• becomes less dense.

• becomes denser.

• can hold more moisture.

• two of the above

The winds blow in the opposite directions in the Southern Hemisphere. The winds do not blow due north or south because of the Coriolis effect. It deflects winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Multiple Choice

Land and sea breezes

• may occur daily and seasonally.

• are types of local winds.

• occur because of differences in specific heat.

• all of the above

Multiple Choice

India is well known for its local winds called

• katabatic winds.

• . monsoon winds.

• Chinook winds

• Santa Ana winds.

Multiple Choice

A rainshadow occurs

• on the leeward size of a mountain.

• where moist air sinks to the ground

• in a low-pressure zone.

• all of the above

Multiple Choice

In global atmospheric circulation

• warm air sinks at the equator.

• warm air flows north from the equator.

• warm air flows south from the equator.