9th Grade Chapter 2 Lesson 4

9 th Grade: Chapter 2 Lesson 4 Pgs. 39-49 For Student Use Only

Patterns of Circulation
Atmosphere
The atmosphere constantly moves because of the uneven heating of across the surface of the earth.
Rising Air= low pressure. This is called a LOW pressure region
Cooling air= high pressure. This is called a HIGH pressure region
Are always moves from high to low pressure.

Air Currents
Unequal heating of the earth also causes major air movements from the poles to the equator
These are GLOBAL CONVECTION CURRENTS!

Global Wind Zones

Winds
Normally winds would travel North to South, but the Earth spins.
This spinning is called the CORIOLIS EFFECT.
Coriolis Effect: The change in course of the winds due to the earth’s rotation.
Coriolis Effect: Works because of Inertia and Speed.

Winds:
Coriolis Effect:
Factors that affect the Coriolis Effect :
Inertia- an object in motion will stay in motion at a constant speed and direction until an outside force acts upon it.
Speed: Objects at different distances from the axis travel and different speeds.
Closer to the axis slower speeds, farther from the axis faster speeds.

Coriolis Effect:
The earth’s surface will outrun objects.
This appears to make them curve in the air.
The object stays at the same speed and direction, but the earth moves.
This movement also causes the winds to appear to shift!

Earth’s Movement and Winds:
Cyclone: circles counterclockwise as the air rushes towards the low pressure area
Anticyclone: circles clockwise as the air rushes from the high pressure area

Earth’s Global Wind Zones
Equatorial Zone: (at the Equator) Where warm air rises called the ITCZ (Inter-Tropical Convergence Zone)
Doldrums: Area of light breezes or no breezes due to the rising motion of the air
Horse Latitudes: (30 ° North and South) where cooler air sinks, little to no breezes. People used to have to dump their horses.

Trade Winds: These are where the winds blow towards the equator.
Northern Hemisphere- blow from the Northeast to the Southwest (called the Northeast Trade Winds)
Southern Hemisphere- blow from the Southeast to the Northwest (called the Southeast Trade Winds)

Polar Easterlies: Winds blow away from poles to the lower latitudes.
Northern Hemisphere- blow out of the Northeast.
Southern Hemisphere- blow out of the Southeast
Prevailing Westerlies: Winds that blow up from the horse latitudes and rush to fill in the warmed polar air.
Northern Hemisphere- blow out of the Southwest
Southern Hemisphere- blow out of the Northwest
Jet Stream: Winds in the upper troposphere that move quickly and meander around

Local Winds:
Not global- found only in certain areas.
Monsoons- Seasonal change in wind (winds reverse directions) which causes a dry season and a wet season. Caused by uneven heating of large land and water masses.
Sea and Land Breezes- Daily switching of wind direction due to uneven heating of land and water.
Sea Breeze: Cooler air from the sea blows into shore in the afternoon.
Land Breeze- At night the cooler air over the land blows out from the land to the sea.

Local Winds:
Mountain Breezes: At night cooler air rushes down from the mountain into the warmer valley.
Valley Breezes: In the day cooler air from the valley rushes into the warmer mountain air.

9th Grade Chapter 2 Lesson 4

by MRS.KDUNCAN

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