2 What is air pressure? The force exerted by air molecules as they collide with a surfaceThe weight of the atmosphere as itpushes on Earth’s surface
3 What is air pressure? Air has mass Gravity pulls these molecules towards Earth giving them weightThe weight of the molecules is air pressurekg
4 What is air pressure?At sea level the weight of air pushing down is 14.7 pounds per square inchThe 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
5 What is air pressure?Air pressure is exerted (pushes) in all directionsAn equal force pushing down is balanced by air pushing up
6 What Is Air Pressure? The same thing as gravity The weight of the atmosphere pushing downwardA form of pollutant
7 Why Don’t We Get Crushed By The Pressure Of The Atmosphere? The air is not that heavyAir pressure is exerted in all directions, and we are in equilibriumThe water in our bodies prevents it
8 Why Did The Oil Drum Collapse? The water weakened itThe atmosphere suddenly got heavierThe 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 pressure2 types of barometersMercuryAneroidMercury 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 barometerA capsule with most of the air removed changes size as the pressure outside of it increases or decreasesThis moves the needle
13 Measuring air pressure Pressure will be measured inMm HgInches of HgMilibarsAverage Pressure at sea levelmb = in. Hg
14 Why does air pressure change? 3 factors that affect pressure:Elevation/Altitude (p414)Temperature (p416)Humidity (p416)
15 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 decreasesAs the altitude decreases pressure increases
17 Changes in air pressure Altitude DrawingHigh Altitude / Low PressureLow Altitude / High Pressure
18 Changes in air pressure Humidity(the amount of water vapor in air)Water molecules weigh less than O2 or N2Water vapor replaces these molecules in humid airAs humidity increases, pressure decreasesAs humidity decreases, pressure increasesHUMID AIRDRY AIR
19 Changes in Air Pressure Humidity DrawingLow Humidity / High PressureHigh Humidity / Low Pressure
20 Changes in air pressure TemperatureIn warm air the molecules are far apart.In cool air the molecules are closer togetherAs air temperature increases, pressure decreasesAs air temperature decreases, pressure increases
21 Changes in air pressure Temperature DrawingHigh Temperature / Low PressureLow Temperature / High Pressure
22 Let’s Summarize Temperature Altitude Decrease Pressure Increase Humidity
23 Low Pressure Generally associated with stormy weather. The air is rising.
24 High PressureGenerally associated with clear skies.Air is sinking.
34 Factors Affecting Wind Direction Coriolis Effect Coriolis-2.mp4Pressure Gradients (differences in pressure HIGH vs LOW)Friction (resistance)
35 The Coriolis EffectAn object moving over Earth’s surface will curve away from its intended pathThis is due to Earth’s rotationFaster at the equatorSlower at the poles
36 The Coriolis Effect Coriolis-1.mp4 Guidelines (p419): objects are deflected to the RIGHT in the Northern Hemisphere and the LEFT in the Southern HemisphereThe effect (curve) increases as the speed increasesThe effect DOES NOT depend on the objects directionThe effect is greater at the poles and less at the equatorMost noticeable of large distances (Not in TOILETS)
38 Pressure Gradients Pressure gradient: A difference in pressure from one place to anotherRemember wind blows from HIGH to LOWThe stronger the gradient the faster the windThe 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 blowThe higher above the surface the more curve due to Coriolis
40 FrictionLittle 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 StatesAffects airplanes as they travel coast to coast
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? Altitude, Humidity, and TemperatureAltitude, Humidity, and Coriolis EffectCoriolis, Pressure, Gradients, and Friction
44 What are the 3 factors that affect air pressure? Altitude, Humidity, and TemperatureCoriolis, Pressure, Gradients, and FrctionSunlight, Convection, and Friction
45 How does a pressure gradient affect the speed of wind? The stronger the gradient, the weaker the windThe stronger the gradient, the stronger the windIt does not effect the speed
46 Why does the Coriolis Effect cause wind to deflect? The wind was already curving; the Coriolis Effect only effects airplanesThe spinning of the Earth causes the path to curve
47 How does friction affect wind speed? Objects or rough surfaces cause a drag on the windFriction makes the wind fasterFriction creates wind
49 Global WindsGlobal winds show the general direction the air is flowing throughout the globe.Refer to your worksheet for these windsThe winds are named according to where the wind comes from or originatesEx. 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 WindsMonsoonLocal WindsSea breezeLand breezeSanta Ana Winds
52 MonsoonA 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 WindsOccur in Southern California in the late fall/early winterA high pressure forms as the desert regionsAs the air sinks it is compressed and usually warms.
56 Santa Ana WindsThis 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? North and South Pole Only0 and 60 Degrees Latitude30 and 90 Degrees LatitudeOver the Ocean
58 Where will you find areas of low pressure on Earth? North and South Pole Only0 and 60 Degrees Latitude30 and 90 Degrees LatitudeOver the Ocean
59 What Creates Santa Ana Winds? High Pressure Over Land and Low Pressure Over OceanLow Pressure Over Land and High Pressure Over OceanPoliticians In Santa Ana