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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.

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Presentation on theme: "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."— Presentation transcript:

1 Air Pressure and Wind

2 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 Earths surface

3 What is air pressure? Air has mass Gravity pulls these molecules towards Earth giving them weight The weight of the molecules is air pressure

4 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 dont all of our houses collapse? Or Why arent we all squished? CHECK THIS OUT!!! Extreme Atmospheric Pressure

5 What is air pressure? Air pressure is exerted (pushes) in all directions An equal force pushing down is balanced by air pushing up

6 What Is Air Pressure? 1.The same thing as gravity 2.The weight of the atmosphere pushing downward 3.A form of pollutant

7 Why Dont We Get Crushed By The Pressure Of The Atmosphere? 1.The air is not that heavy 2.Air pressure is exerted in all directions, and we are in equilibrium 3.The water in our bodies prevents it

8 Why Did The Oil Drum Collapse? 1.The water weakened it 2.The atmosphere suddenly got heavier 3.The cooling vapor took up less space than before and created a drop in pressure inside. The regular air pressure then crushed the drum.

9 Measuring air pressure The barometer is the instrument used to measure air pressure 2 types of barometers –Mercury –Aneroid Mercury Barometer

10 Measuring air pressure As the weight of the air increases, the mercury rises

11 Measuring air pressure As the weight of the air decreases, the mercury lowers

12 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

13 Measuring air pressure Pressure will be measured in –Mm Hg –Inches of Hg –Milibars Average Pressure at sea level – mb = in. Hg

14 Why does air pressure change? 3 factors that affect pressure: –Elevation/Altitude (p414) –Temperature (p416) –Humidity (p416)

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

16 Changes in air pressure Altitude (height above sea level) As the altitude increases pressure decreases As the altitude decreases pressure increases

17 Changes in air pressure Altitude Drawing High Altitude / Low Pressure Low Altitude / High Pressure

18 Changes in air pressure Humidity (the amount of water vapor in air) –Water molecules weigh less than O 2 or N 2 –Water vapor replaces these molecules in humid air As humidity increases, pressure decreases As humidity decreases, pressure increases HUMID AIR DRY AIR

19 Changes in Air Pressure Humidity Drawing Low Humidity / High Pressure High Humidity / Low Pressure

20 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

21 Changes in air pressure Temperature Drawing High Temperature / Low PressureLow Temperature / High Pressure

22 Lets Summarize DecreasePressureIncreasePressure Temperature Altitude Humidity

23 Low Pressure Generally associated with stormy weather. The air is rising.

24 High Pressure Generally associated with clear skies. Air is sinking.

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26 What does a barometer measure? 1.Atmospheric pressure 2.The humidity of the air 3.Air quality 4.How much it has rained

27 What affects air pressure? 1.Altitude 2.Humidity 3.Temperature 4.All of the above

28 Why is water vapor less dense than air? 1.There is less of it 2.H 2 O has less mass than O 2 or N 2 3.It is hotter, so it has less mass

29 Low pressure is usually associated with… 1.Sunny skies 2.Deserts 3.Earthquakes 4.Stormy weather and rising air

30 High pressure is usually associated with… 1.Rain 2.Tornadoes 3.Sunny, dry weather with sinking air 4.Pushy car salesmen

31 Factors Affecting Wind Direction and Speed

32 What makes the wind blow? Air moves from HIGH PRESSURE to LOW PRESSURE This movement of air is WIND

33 What makes the wind blow? Island Example

34 Factors Affecting Wind Direction Coriolis EffectCoriolis-2.mp4Coriolis-2.mp4 Pressure Gradients (differences in pressure HIGH vs LOW) Friction (resistance)

35 The Coriolis Effect An object moving over Earths surface will curve away from its intended path This is due to Earths rotation –Faster at the equator –Slower at the poles

36 The Coriolis Effect 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

37 The Coriolis Effect Lets Draw!

38 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

39 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

40 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

41 Jet Stream

42 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?

43 What are the 3 factors that affect wind direction? 1.Altitude, Humidity, and Temperature 2.Altitude, Humidity, and Coriolis Effect 3.Coriolis, Pressure, Gradients, and Friction

44 What are the 3 factors that affect air pressure? 1.Altitude, Humidity, and Temperature 2.Coriolis, Pressure, Gradients, and Frction 3.Sunlight, Convection, and Friction

45 How does a pressure gradient affect the speed of wind? 1.The stronger the gradient, the weaker the wind 2.The stronger the gradient, the stronger the wind 3.It does not effect the speed

46 Why does the Coriolis Effect cause wind to deflect? 1.The wind was already curving; the Coriolis Effect only effects airplanes 2.The spinning of the Earth causes the path to curve

47 How does friction affect wind speed? 1.Objects or rough surfaces cause a drag on the wind 2.Friction makes the wind faster 3.Friction creates wind

48 Global and Local Winds

49 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?

50 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

51 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

52 Monsoon A Monsoon is a seasonal change in winds. Ex. India, North America

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

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

55 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.

56 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

57 Where will you find areas of high pressure on Earth? 1.North and South Pole Only 2.0 and 60 Degrees Latitude 3.30 and 90 Degrees Latitude 4.Over the Ocean

58 Where will you find areas of low pressure on Earth? 1.North and South Pole Only 2.0 and 60 Degrees Latitude 3.30 and 90 Degrees Latitude 4.Over the Ocean

59 What Creates Santa Ana Winds? 1.High Pressure Over Land and Low Pressure Over Ocean 2.Low Pressure Over Land and High Pressure Over Ocean 3.Politicians In Santa Ana

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