Global Winds - PowerPoint Presentation

Slide1

Global Winds

Unit 5: Sixth Grade

http://www.youtube.com/watch?v=uBqohRu2RRkSlide2

https://games.ciconline.org/windward/content/sailing.html#record

Windward Online Sailing around the world gameSlide3

Whooosh!!!!!

When you open the valve on a bicycle tube, the air rushes out.

Why?

The air inside the tube is at a higher pressure than the air outside the tube.

This is similar to how winds are formed!Slide4

Wind

The movement of air cause by differences in air pressure is called

wind

The

greater

the pressure

difference

, the

faster

the wind moves.Slide5

Rising and Sinking

Differences in air pressure are generally due to the

unequal heating and

temperature differences

o f the earth.

Remember,

warm air is less dense and will rise.

Cool air

is more dense and sinksSlide6

Air Rises at the Equator

The

equator

receives more direct solar energy (radiant heating) than other latitudes, so air at the equator is

warmer

and

less dense

than the surrounding air.

Lighter,

one blanket

Warm, less dense air

rises

and creates an area

of low pressure.

This warm, rising air flows

toward the poles

.Slide7

Air Sinks at the Poles

However, at the

poles

, the air is

colder

and

denser than the surrounding air, so it sinks

.

Heavier,

many blankets

This sinking air creates an area of high pressure

around the poles

This cold polar air then flows

toward the equatorSlide8

Air blows from high to low!!

Low Pressure

Rising, warmer air

Moist: Clouds, rain, snow, strong winds, warmer air

Snow means low!

High Pressure

Sinking, colder air

Dry: Clear skies, sunshine, cool air, little wind

High and Dry!Slide9

You may imagine that wind moves in one huge, circular pattern from the poles to the equator.

In fact, air travels in many large circular patterns called

convection cells

Convection = circulation (moving air)

These convection cells are separated by

pressure belts, which are bands of high or low pressure. These belts are found about every

30* latitude

Pressure BeltsSlide10

Pressure

Belts

http://www.youtube.com/watch?v=v7CaZOTXCSoSlide11

Pressure Belts

As warm air rises over the equator and moves toward the poles, the air begins to cool.

At about 30* North and 30*South latitude, some of this cool air begins to

sinkSlide12

Pressure Belts

This cool sinking air, causes

high pressure

around

30*

N and S latitude.This cooled air

flows back to the equator, where it warms again, and rises.Slide13

And the same thing is happening at the poles, just in reverse!

At the poles, the cold air

sinks

, and moves toward the

equator

.

The air

warms

as it moves toward the equator.

Around

60* N and S latitude, the warmer air rises, which creates a

low pressure belt.

This air then flows back to the

polesSlide14

The Coriolis

Effect

Pressure differences cause the air to move between the equator and the poles.

But due to the earth’s rotation, the air does not move in straight lines!

This apparent curving of the path of winds is called the

Coriolis

Effect

.Slide15

Coriolis Effect

Because of the

Coriolis

Effect, winds traveling north in the

Northern

Hemisphere curve to the

east

, and winds traveling

south

curve to the

west.How would the Southern Hemisphere compare?

http://www.phschool.com/atschool/phsciexp/active_art/global_winds/index.htmlSlide16

The combination of convection cells found at every 30* latitude and the

Coriolis

Effect produces patterns of air circulation called

Global Winds

.

The major global wind systems are the Polar Easterlies, Westerlies, and Trade Winds.Winds such as the Easterlies and

Westerlies are named for the direction from which they blow

Global WindsSlide17

Polar Easterlies

The wind belts that extend from the

poles to 60*

latitude.

They are formed when cold, sinking air (

high pressure

) moves from the poles toward 60* north and south latitudePolar Easterlies can carry

cold, arctic air

over the US, producing snow and freezing weatherSlide18

Westerlies

The wind belts found between

30* and 60*

latitude.

They flow toward the poles from

west to east.

Can carry

moist air,

producing rain or snow (low pressure)Slide19

Trade Winds

Winds that blow from

30*

latitude almost to the

equator

are the trade winds.

They are warm, steady breezes

that blow almost

continuously (low pressure).

The

Coriolis Effect makes the trade winds appear to be curving to the west in the Northern HemisphereSlide20

The Doldrums

The trade winds of the N and S hemispheres meet in an area around the equator called the

doldrums

.

There is

very little wind

because the warm rising air creates an area of low pressure.

Doldrums means “dull” or “sluggish”Slide21

The Horse Latitudes

At about

30* N and S

latitude, sinking air creates an area of

high pressure

.The winds at these locations are weak.

Most of the world’s deserts

are located here because the sinking air is very drySlide22

Jets Stream

Jet streams

are narrow belts of high-speed winds that blow in the upper troposphere and lower stratosphere.

They can blow as fast as 400 km/

hr

They do

not follow regular paths around the earth.

They help pilots and meteorologistsSlide23
Slide24

Local winds generally move

short

distances and can blow from

any

direction.

Local geographic features, such as a shoreline or a

mountain can produce temperature differences that can cause local winds

Local WindsSlide25

Sea Breezes

http://www.youtube.com/watch?v=gM0d3fGew-0&feature=relatedSlide26

Land Breeze

At night, the land cools of faster than the sea.

Cooler air descends creating an area of high pressure.

Wind blows from land to sea. Slide27

Sea Breeze

During the day, land gets hotter faster.

Hot air rises, creating an area of low pressure.

Wind blows from the sea to the land Slide28

Local Winds

Land heat and cools more rapidly than does the sea.

Water retains heat longer than does land, and also takes longer to heat and cool. The ocean regulates temperatures of coastal lands because oceans change temperature slowly.

This causes temperature differences between land sea. Slide29

Mountain and Valley BreezesSlide30

So why is coastal Georgia usually warmer than Douglasville in winter?Slide31