2What 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
3What is air pressure? Air has mass Gravity pulls these molecules towards Earth giving them weightThe weight of the molecules is air pressurekg
4What 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
5What is air pressure?Air pressure is exerted (pushes) in all directionsAn equal force pushing down is balanced by air pushing up
6What Is Air Pressure? The same thing as gravity The weight of the atmosphere pushing downwardA form of pollutant
7Why 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
8Why 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.
9Measuring air pressure The barometer is the instrument used to measure air pressure2 types of barometersMercuryAneroidMercury Barometer
10Measuring air pressure As the weight of the air increases, the mercury rises
11Measuring air pressure As the weight of the air decreases, the mercury lowers
12Measuring 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
13Measuring air pressure Pressure will be measured inMm HgInches of HgMilibarsAverage Pressure at sea levelmb = in. Hg
14Why does air pressure change? 3 factors that affect pressure:Elevation/Altitude (p414)Temperature (p416)Humidity (p416)
15Complete the graphic organizer by filling in the 3 factors that affect pressure. Then create branches explaining how they cause pressure to change.
16Changes in air pressure Altitude(height above sea level)As the altitude increases pressure decreasesAs the altitude decreases pressure increases
17Changes in air pressure Altitude DrawingHigh Altitude / Low PressureLow Altitude / High Pressure
18Changes 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
19Changes in Air Pressure Humidity DrawingLow Humidity / High PressureHigh Humidity / Low Pressure
20Changes 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
21Changes in air pressure Temperature DrawingHigh Temperature / Low PressureLow Temperature / High Pressure
22Let’s Summarize Temperature Altitude Decrease Pressure Increase Humidity
23Low Pressure Generally associated with stormy weather. The air is rising.
24High PressureGenerally associated with clear skies.Air is sinking.
34Factors Affecting Wind Direction Coriolis Effect Coriolis-2.mp4Pressure Gradients (differences in pressure HIGH vs LOW)Friction (resistance)
35The 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
36The 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)
38Pressure 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
39Friction 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
40FrictionLittle 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
42Review 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?
43What are the 3 factors that affect wind direction? Altitude, Humidity, and TemperatureAltitude, Humidity, and Coriolis EffectCoriolis, Pressure, Gradients, and Friction
44What are the 3 factors that affect air pressure? Altitude, Humidity, and TemperatureCoriolis, Pressure, Gradients, and FrctionSunlight, Convection, and Friction
45How 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
46Why 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
47How does friction affect wind speed? Objects or rough surfaces cause a drag on the windFriction makes the wind fasterFriction creates wind
49Global 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?
50Global 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
51Continental 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
52MonsoonA Monsoon is a seasonal change in winds.Ex. India, North America
53Sea Breeze: Rising Air, Sinking Air, High Pressure, Low Pressure, Dense Air, Less Dense Air, Cloud Formation
54Land Breeze: Rising Air, Sinking Air, High Pressure, Low Pressure, Dense Air, Less Dense Air,
55Santa 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.
56Santa Ana WindsThis creates an offshore wind (blows towards the ocean)The air is very dry and often wildfires are a result of this wind
57Where will you find areas of high pressure on Earth? North and South Pole Only0 and 60 Degrees Latitude30 and 90 Degrees LatitudeOver the Ocean
58Where will you find areas of low pressure on Earth? North and South Pole Only0 and 60 Degrees Latitude30 and 90 Degrees LatitudeOver the Ocean
59What Creates Santa Ana Winds? High Pressure Over Land and Low Pressure Over OceanLow Pressure Over Land and High Pressure Over OceanPoliticians In Santa Ana