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# Air Pressure and Wind - PowerPoint PPT Presentation

Air Pressure and Wind. The force exerted by air molecules as they collide with a surface The weight of the atmosphere as it pushes on Earth’s surface. What is air pressure?. Air has mass Gravity pulls these molecules towards Earth giving them weight

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Presentation Transcript

### Air Pressure and Wind

The force exerted by air molecules

as they collide with a surface

The weight of the atmosphere as it

pushes on Earth’s surface

What is air pressure?

Air has mass

Gravity pulls these molecules towards Earth giving them weight

The weight of the molecules is air pressure

kg

What is air pressure?

• At sea level the weight of air pushing down is 14.7 pounds per square inch

• The weight on the roof of a typical house is about 2.1 million kg (4.6 million lbs)

Why don’t all of our houses collapse?

Or Why aren’t we all squished?

CHECK THIS OUT!!!

Extreme Atmospheric Pressure

Air pressure is exerted (pushes) in all directions

An equal force pushing down is balanced by air pushing up

What is air pressure?

• The same thing as gravity

• The weight of the atmosphere pushing downward

• A form of pollutant

• The air is not that heavy

• Air pressure is exerted in all directions, and we are in equilibrium

• The water in our bodies prevents it

Why Did The Oil Drum Collapse? Atmosphere?

• The water weakened it

• The atmosphere suddenly got heavier

• The cooling vapor took up less space than before and created a drop in pressure inside. The regular air pressure then crushed the drum.

2 types of barometers

Mercury

Aneroid

Mercury Barometer

Measuring air pressure

Measuring air pressure Atmosphere?

• As the weight of the air increases, the mercury rises

Measuring air pressure Atmosphere?

• As the weight of the air decreases, the mercury lowers

Measuring air pressure Atmosphere?

The Aneroid barometer

• A capsule with most of the air removed changes size as the pressure outside of it increases or decreases

• This moves the needle

Measuring air pressure Atmosphere?

• Pressure will be measured in

• Mm Hg

• Inches of Hg

• Milibars

• Average Pressure at sea level

• 1013.25 mb = 29.92 in. Hg

Why does air pressure change? Atmosphere?

• 3 factors that affect pressure:

• Elevation/Altitude (p414)

• Temperature (p416)

• Humidity (p416)

Complete the graphic organizer by filling in the 3 factors that affect pressure. Then create branches explaining how they cause pressure to change.

Changes in air pressure that affect pressure. Then create branches explaining how they cause pressure to change.

• Altitude

(height above sea level)

• As the altitude increases pressure decreases

• As the altitude decreases pressure increases

Changes in air pressure that affect pressure. Then create branches explaining how they cause pressure to change.

Altitude Drawing

High Altitude / Low Pressure

Low Altitude / High Pressure

Changes in air pressure that affect pressure. Then create branches explaining how they cause pressure to change.

Humidity

(the amount of water vapor in air)

• Water molecules weigh less than O2 or N2

• Water vapor replaces these molecules in humid air

• As humidity increases, pressure decreases

• As humidity decreases, pressure increases

HUMID AIR

DRY AIR

Humidity Drawing that affect pressure. Then create branches explaining how they cause pressure to change.

Changes in Air Pressure

Low Humidity / High Pressure

High Humidity / Low Pressure

Changes in air pressure that affect pressure. Then create branches explaining how they cause pressure to change.

Temperature

• In warm air the molecules are far apart.

• In cool air the molecules are closer together

• As air temperature increases, pressure decreases

• As air temperature decreases, pressure increases

Changes in air pressure that affect pressure. Then create branches explaining how they cause pressure to change.

Temperature Drawing

High Temperature / Low Pressure

Low Temperature / High Pressure

Let’s Summarize that affect pressure. Then create branches explaining how they cause pressure to change.

Low Pressure that affect pressure. Then create branches explaining how they cause pressure to change.

Generally associated with stormy weather.

The air is rising.

High Pressure that affect pressure. Then create branches explaining how they cause pressure to change.

Generally associated with clear skies.

Air is sinking.

What makes the wind blow? that affect pressure. Then create branches explaining how they cause pressure to change.

• Air moves from

HIGH PRESSURE to LOW PRESSURE

• This movement of air is WIND

What does a barometer measure? that affect pressure. Then create branches explaining how they cause pressure to change.

• Atmospheric pressure

• The humidity of the air

• Air quality

• How much it has rained

What affects air pressure? that affect pressure. Then create branches explaining how they cause pressure to change.

• Altitude

• Humidity

• Temperature

• All of the above

Why is water vapor less dense than air? that affect pressure. Then create branches explaining how they cause pressure to change.

• There is less of it

• H2O has less mass than O2 or N2

• It is hotter, so it has less mass

Low pressure is usually associated with… that affect pressure. Then create branches explaining how they cause pressure to change.

• Sunny skies

• Deserts

• Earthquakes

• Stormy weather and rising air

High pressure is usually associated with… that affect pressure. Then create branches explaining how they cause pressure to change.

• Rain

• Sunny, dry weather with sinking air

• Pushy car salesmen

### Factors Affecting Wind Direction and Speed that affect pressure. Then create branches explaining how they cause pressure to change.

What makes the wind blow? that affect pressure. Then create branches explaining how they cause pressure to change.

• Island Example

Factors Affecting Wind Direction that affect pressure. Then create branches explaining how they cause pressure to change.

• Coriolis Effect Coriolis-2.mp4

• Pressure Gradients (differences in pressure HIGH vs LOW)

• Friction (resistance)

The Coriolis Effect that affect pressure. Then create branches explaining how they cause pressure to change.

• An object moving over Earth’s surface will curve away from its intended path

• This is due to Earth’s rotation

• Faster at the equator

• Slower at the poles

Guidelines (p419): that affect pressure. Then create branches explaining how they cause pressure to change.

objects are deflected to the RIGHT in the Northern Hemisphere and the LEFT in the Southern Hemisphere

The effect (curve) increases as the speed increases

The effect DOES NOT depend on the objects direction

The effect is greater at the poles and less at the equator

Most noticeable of large distances (Not in TOILETS)

Coriolis-1.mp4

The Coriolis Effect

The Coriolis Effect that affect pressure. Then create branches explaining how they cause pressure to change.

• Let’s Draw!

Pressure Gradients that affect pressure. Then create branches explaining how they cause pressure to change.

• A difference in pressure from one place to another

• Remember wind blows from HIGH to LOW

• The stronger the gradient the faster the wind

• The faster the wind the more curve from the Coriolis Effect

Friction that affect pressure. Then create branches explaining how they cause pressure to change.

• Friction between the air and the ground slows wind.

• The higher above the surface the faster the wind will blow

• The higher above the surface the more curve due to Coriolis

Friction that affect pressure. Then create branches explaining how they cause pressure to change.

• Little friction in the upper troposphere allows a jet stream to from moving air west to east.

• The jet stream supplies energy to storms and directs the path of weather across the United States

• Affects airplanes as they travel coast to coast

Jet Stream that affect pressure. Then create branches explaining how they cause pressure to change.

Review Questions that affect pressure. Then create branches explaining how they cause pressure to change.

• What are the 3 factors that affect wind direction?

• What are the 3 factors that affect air pressure?

• How does a pressure gradient affect the speed of wind? Direction of wind?

• Why does the Coriolis Effect cause wind to deflect?

• Can you witness the Coriois Effect in your bathroom?

• How does friction affect wind speed?

What are the 3 factors that affect wind direction? that affect pressure. Then create branches explaining how they cause pressure to change.

• Altitude, Humidity, and Temperature

• Altitude, Humidity, and Coriolis Effect

• Coriolis, Pressure, Gradients, and Friction

What are the 3 factors that affect air pressure? that affect pressure. Then create branches explaining how they cause pressure to change.

• Altitude, Humidity, and Temperature

• Coriolis, Pressure, Gradients, and Frction

• Sunlight, Convection, and Friction

How does a pressure gradient affect the speed of wind? that affect pressure. Then create branches explaining how they cause pressure to change.

• The stronger the gradient, the weaker the wind

• The stronger the gradient, the stronger the wind

• It does not effect the speed

Why does the Coriolis Effect cause wind to deflect? that affect pressure. Then create branches explaining how they cause pressure to change.

• The wind was already curving; the Coriolis Effect only effects airplanes

• The spinning of the Earth causes the path to curve

How does friction affect wind speed? that affect pressure. Then create branches explaining how they cause pressure to change.

• Objects or rough surfaces cause a drag on the wind

• Friction makes the wind faster

• Friction creates wind

### Global and Local Winds that affect pressure. Then create branches explaining how they cause pressure to change.

Global Winds that affect pressure. Then create branches explaining how they cause pressure to change.

• Global winds show the general direction the air is flowing throughout the globe.

• Refer to your worksheet for these winds

• The winds are named according to where the wind comes from or originates

• Ex. What would the name of this wind be?

Global Winds that affect pressure. Then create branches explaining how they cause pressure to change.

Climate Zones due to global winds:

• Areas of low pressure are characterized by rising air, precipitation = Rainforest (0, 60)

• Areas of high pressure are characterized by sinking air, dry air = Deserts (30, 90)

Continental and Local Winds that affect pressure. Then create branches explaining how they cause pressure to change.

• These winds can go opposite the expected global winds due to changes in local conditions:

• Continental Winds

• Monsoon

• Local Winds

• Sea breeze

• Land breeze

• Santa Ana Winds

Monsoon that affect pressure. Then create branches explaining how they cause pressure to change.

A Monsoon is a seasonal change in winds.

Ex. India, North America

Sea Breeze: that affect pressure. Then create branches explaining how they cause pressure to change.Rising Air, Sinking Air, High Pressure, Low Pressure, Dense Air, Less Dense Air, Cloud Formation

Land Breeze: that affect pressure. Then create branches explaining how they cause pressure to change.Rising Air, Sinking Air, High Pressure, Low Pressure, Dense Air, Less Dense Air,

Santa Ana Winds that affect pressure. Then create branches explaining how they cause pressure to change.

• Occur in Southern California in the late fall/early winter

• A high pressure forms as the desert regions

• As the air sinks it is compressed and usually warms.

Santa Ana Winds that affect pressure. Then create branches explaining how they cause pressure to change.

• This creates an offshore wind (blows towards the ocean)

• The air is very dry and often wildfires are a result of this wind

Where will you find areas of high pressure on Earth? that affect pressure. Then create branches explaining how they cause pressure to change.

• North and South Pole Only

• 0 and 60 Degrees Latitude

• 30 and 90 Degrees Latitude

• Over the Ocean

Where will you find areas of low pressure on Earth? that affect pressure. Then create branches explaining how they cause pressure to change.

• North and South Pole Only

• 0 and 60 Degrees Latitude

• 30 and 90 Degrees Latitude

• Over the Ocean

What Creates Santa Ana Winds? that affect pressure. Then create branches explaining how they cause pressure to change.

• High Pressure Over Land and Low Pressure Over Ocean

• Low Pressure Over Land and High Pressure Over Ocean

• Politicians In Santa Ana