Air pressure and wind
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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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Air Pressure and Wind

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Air pressure and wind

Air Pressure and Wind


What is air pressure

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?


What is air pressure1

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?


What is air pressure2

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


What is air pressure3

Air pressure is exerted (pushes) in all directions

An equal force pushing down is balanced by air pushing up

What is air pressure?


What is air pressure4

What Is Air Pressure?

  • The same thing as gravity

  • The weight of the atmosphere pushing downward

  • A form of pollutant


Why don t we get crushed by the pressure of the atmosphere

Why Don’t We Get Crushed By The Pressure Of The Atmosphere?

  • 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

Why Did The Oil Drum Collapse?

  • 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.


Measuring air pressure

The barometer is the instrument used to measure air pressure

2 types of barometers

Mercury

Aneroid

Mercury Barometer

Measuring air pressure


Measuring air pressure1

Measuring air pressure

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


Measuring air pressure2

Measuring air pressure

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


Measuring air pressure3

Measuring air pressure

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 pressure4

Measuring air pressure

  • 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

Why does air pressure change?

  • 3 factors that affect pressure:

    • Elevation/Altitude (p414)

    • Temperature (p416)

    • Humidity (p416)


Air pressure and wind

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

Changes in air pressure

  • Altitude

    (height above sea level)

    • As the altitude increases pressure decreases

    • As the altitude decreases pressure increases


Changes in air pressure1

Changes in air pressure

Altitude Drawing

High Altitude / Low Pressure

Low Altitude / High Pressure


Changes in air pressure2

Changes in air pressure

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


Changes in air pressure3

Humidity Drawing

Changes in Air Pressure

Low Humidity / High Pressure

High Humidity / Low Pressure


Changes in air pressure4

Changes in air pressure

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 pressure5

Changes in air pressure

Temperature Drawing

High Temperature / Low Pressure

Low Temperature / High Pressure


Let s summarize

Let’s Summarize


Low pressure

Low Pressure

Generally associated with stormy weather.

The air is rising.


High pressure

High Pressure

Generally associated with clear skies.

Air is sinking.


What makes the wind blow

What makes the wind blow?

  • Air moves from

    HIGH PRESSURE to LOW PRESSURE

  • This movement of air is WIND


What does a barometer measure

What does a barometer measure?

  • Atmospheric pressure

  • The humidity of the air

  • Air quality

  • How much it has rained


What affects air pressure

What affects air pressure?

  • Altitude

  • Humidity

  • Temperature

  • All of the above


Why is water vapor less dense than air

Why is water vapor less dense than air?

  • 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

Low pressure is usually associated with…

  • Sunny skies

  • Deserts

  • Earthquakes

  • Stormy weather and rising air


High pressure is usually associated with

High pressure is usually associated with…

  • Rain

  • Tornadoes

  • Sunny, dry weather with sinking air

  • Pushy car salesmen


Factors affecting wind direction and speed

Factors Affecting Wind Direction and Speed


What makes the wind blow1

What makes the wind blow?

  • Island Example


Factors affecting wind direction

Factors Affecting Wind Direction

  • Coriolis EffectCoriolis-2.mp4

  • Pressure Gradients (differences in pressure HIGH vs LOW)

  • Friction (resistance)


The coriolis effect

The Coriolis Effect

  • 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


The coriolis effect1

Guidelines (p419):

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 effect2

The Coriolis Effect

  • Let’s Draw!


Pressure gradients

Pressure Gradients

  • Pressure gradient:

    • 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

Friction

  • 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


Friction1

Friction

  • 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

Jet Stream


Review questions

Review Questions

  • 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

What are the 3 factors that affect wind direction?

  • Altitude, Humidity, and Temperature

  • Altitude, Humidity, and Coriolis Effect

  • Coriolis, Pressure, Gradients, and Friction


What are the 3 factors that affect air pressure

What are the 3 factors that affect air pressure?

  • Altitude, Humidity, and Temperature

  • Coriolis, Pressure, Gradients, and Frction

  • Sunlight, Convection, and Friction


How does a pressure gradient affect the speed of wind

How does a pressure gradient affect the speed of wind?

  • 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

Why does the Coriolis Effect cause wind to deflect?

  • 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

How does friction affect wind speed?

  • Objects or rough surfaces cause a drag on the wind

  • Friction makes the wind faster

  • Friction creates wind


Global and local winds

Global and Local Winds


Global winds

Global Winds

  • 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 winds1

Global Winds

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)

    ** Add these areas to your worksheet


Continental and local winds

Continental and Local Winds

  • 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


Air pressure and wind

Monsoon

A Monsoon is a seasonal change in winds.

Ex. India, North America


Air pressure and wind

Sea Breeze:Rising Air, Sinking Air, High Pressure, Low Pressure, Dense Air, Less Dense Air, Cloud Formation


Land breeze rising air sinking air high pressure low pressure dense air less dense air

Land Breeze:Rising Air, Sinking Air, High Pressure, Low Pressure, Dense Air, Less Dense Air,


Santa ana winds

Santa Ana Winds

  • 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 winds1

Santa Ana Winds

  • 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

Where will you find areas of high pressure on Earth?

  • 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

Where will you find areas of low pressure on Earth?

  • North and South Pole Only

  • 0 and 60 Degrees Latitude

  • 30 and 90 Degrees Latitude

  • Over the Ocean


What creates santa ana winds

What Creates Santa Ana Winds?

  • High Pressure Over Land and Low Pressure Over Ocean

  • Low Pressure Over Land and High Pressure Over Ocean

  • Politicians In Santa Ana


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