Air Movement on EarthWind

Outline

– What is wind?– What causes it?– What are some common wind patterns?• Surface winds• Jet stream• Sea and land breezes

• Earth is a rocky, inner planet with liquid water on over 70% of its surface.

• Having two different types of surfaces (land and water) strongly affects the winds produced on Earth.– Which surface heats up more quickly?• Sand

– Which surface cools off more quickly?• Sand

• Which areas of the Earth receive more direct sunlight and therefore are hotter?– Equator gets more direct light and is therefore

hotter

• Do all areas of Earth have the same amount of sunlight all year long?– No! More sunlight hours in summer, therefore it’s

hotter.

• Surface type (land or water) and temperature (affected by direct/indirect light and hours of sunlight) can cause an uneven heating of Earth’s surface.

• As air molecules heat up, they move apart and become less dense– This is called low air pressure

Can you answer this?

Warm air rises because it is less dense

Cold air sinks because it is more dense

What is Wind?• Wind is the movement of air from an area of

high pressure (cold) to an area of low pressure (warm)

Demo on pressure

• Fill the beaker halfway with water• Slowly push the Dixie cup into the beaker, until

the hole is under the water level.• Which way does the water flow?

– It flows into the empty cup-why?• What does this have to do with air pressure?• Air will flow from areas of high pressure to areas

of low pressure, just like water flowed from high pressure area- the beaker, into low pressure area- the cup.

What areas of Earth will have colder (higher pressure) air?

Air near the poles

will be colder and

higher pressure.

The high pressure air from the poles will flow towards the low pressure areas by the equator

• This causes wind• But it doesn’t flow

in a straight line as seen in this picture

• Why?

Wind doesn’t travel in a straight line due to Earth’s rotation on its axis

• Wind (and water) in the Northern Hemisphere will turn to the right

• Wind (and water) in the Southern Hemisphere will turn to the left.

We see this spin in hurricanes

• N. Hemisphere storms spin counter clockwise

• S. Hemisphere storms spin clockwise

In which hemisphere is this hurricane occurring?

Northern Hemisphere, it’s spinning is counter clockwise

This curving of the wind is called the Coriolis Effect

• Does it affect the spinning of the water in my toilet?

• No, the water in the toilet is not a large enough body of water.

https://www.youtube.com/watch?v=rdGtcZSFRLkCoriolis Effect on toilets?

Wind Patterns

• Earth’s surface with different surface materials (land or water)

• Plus, the different amount of solar radiation received (direct or indirect light, and hours of light)

• Plus, the Coriolis effectAll add together to create distinct wind patterns

on Earth.

Common Wind patterns

• Polar Easterlies

• Westerlies• Tradewinds• Doldrums

http://www.youtube.com/watch?v=qh011eAYjAAGlobal winds over a year

Tradewinds were important to early explorers and for trade routes

Jet Stream• A strong belt of wind in the upper

troposphere.• It flows from west to east. • Pilots take advantage of this when they fly to

the East coast.

The jet stream is why we look to the west to find out what type of weather is moving our way.

Local Wind Systems• Local areas near bodies of water experience

smaller scale wind patterns

Sea breeze• During the day, air over the land is heated by

conduction.• The warmer, less dense air rises• The cooler (high pressure) ocean air moves

into the low pressure area, resulting in a sea breeze

Land breeze• At night, air over the land cools quickly.• The cooler, less dense (high pressure) sinks

and moves towards the low pressure (warmer) air over the water.

• Resulting in a land breeze.

Summary

• Warm air is less dense than cool air• Differences in density (temperature) and air

pressure cause air movement- wind• Coriolis effect, Earth’s Rotation, causes the wind to

turn• Wind patterns are observed in different latitudes• A wind pattern seen high in the troposphere is the

jet stream• Sea breezes and land breezes are patterns of air

seen near bodies of water.

Review Videos

• http://earth.nullschool.net/A visualization of global weather conditions forecast by supercomputers updated every three hours (open in Google Chrome) You can spin the globe and zoom in

• http://www.youtube.com/watch?v=6hD52H7rQakThe Sun as the driving force behind for wind and water currents and earth’s temperatures

https://www.youtube.com/watch?v=RzSqhrn2dDMReview of Wind