14.3 Air Movement and Wind

How does the sun cause the air to move?

Wind Movement of air The greater the air pressure, the faster the air moves, and the stronger the wind.

Wind

What causes wind? Differences in air pressure due to the uneven heating of Earth’s surface cause winds. Air moves from area of high pressure to areas of low pressure.

Coriolis effect The apparent curving of the path of winds and ocean currents due to Earth’s rotation.

Coriolis Effect

Global winds Air-circulation patterns produced by a combination of convection cells, pressure belts, winds, and Coriolis effect. Polar easterlies, prevailing westerlies, trade winds

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Local winds Result by differences in pressure that caused by uneven heating of Earth’s surface.

What causes global wind patterns? Convection cells, pressure belts, and winds combine with the Coriolis effect to cause global wind patterns.

Sea breezes and land breezes Daytime – air over the land heats up fast, and a low pressure area forms. A high-pressure area forms over the ocean. Cool air flows toward the land.

Local Winds Move short distances and can blow from any direction.

What causes local winds? Local winds are caused by differences in air pressure that result from the uneven heating of Earth’s surface. This uneven heating is the result of the way in which different materials absorb solar radiation.

Sea breezes and land breezes Evening – high-pressure area forms over the land. Cool air flows toward the ocean. Air over the ocean cools slowly, and a low pressure area forms.

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Valley breezes and mountain breezes Daytime – warm air rises up the mountain slopes creating valley breeze.

Evening – Cool air moves down the slopes into the valley.

Review Questions What causes the Coriolis effect? The rotation of Earth on its axis causes the Coriolis effect.

2. How does the Coriolis effect affect wind movement? The Coriolis effect causes winds to be deflected to the east or west depending on the direction that the winds are traveling in each hemisphere. Because of the Coriolis effect, winds in the Northern Hemisphere curve to the right, and winds in the Southern Hemisphere curve to the left.

How do the processes that cause global winds and local winds differ? Global winds are caused by the uneven heating of Earth’s surface due to the amount of direct sunlight that reaches the ground at different latitudes. Local winds are caused by the uneven heating of Earth’s surface due to the way the different materials absorb and release energy.

Describe the difference between sea and land breezes and between valley and mountain breezes. Sea and land breezes form as a result of the different rates at which land and water heat up and cool down. Mountain and valley breezes form as a result of the topography and the direction in which the air flows when it heats up and cools down.