WindWind

Coriolis Effect (p. 516)Coriolis Effect (p. 516)

Prevailing Winds (p. 516-519)Prevailing Winds (p. 516-519)

Coriolis EffectCoriolis Effect

• The spinning of the Earth creates an The spinning of the Earth creates an effect on any item that is in the air effect on any item that is in the air for a long period of timefor a long period of time– Winds are therefore affectedWinds are therefore affected

• Was discovered by Gustave Coriolis Was discovered by Gustave Coriolis when working with the armywhen working with the army– They couldn’t figure out why their They couldn’t figure out why their

carefully aimed canons weren’t hitting carefully aimed canons weren’t hitting their targettheir target

Coriolis EffectCoriolis Effect

• In the Northern hemisphere, the rotation In the Northern hemisphere, the rotation is to the East (counterclockwise)is to the East (counterclockwise)– Objects will ‘drift’ to the rightObjects will ‘drift’ to the right

• In the Southern hemisphere, the In the Southern hemisphere, the rotation is to the West (clockwise)rotation is to the West (clockwise)– Objects will ‘drift’ to the leftObjects will ‘drift’ to the left

• The Coriolis effect is noticed the least at The Coriolis effect is noticed the least at the equator and the most at the polesthe equator and the most at the poles

WindsWinds

• Some winds are small and regionalSome winds are small and regional

• Many are major wind patterns that Many are major wind patterns that cover large areascover large areas– These winds are called These winds are called Prevailing WindsPrevailing Winds

Wind Patterns (Surface)Wind Patterns (Surface)

• Between 60Between 60° latitude and ° latitude and the polesthe poles– Winds move from East to WestWinds move from East to West– They are called the Polar EasterliesThey are called the Polar Easterlies

W

E

Wind Patterns (Surface)Wind Patterns (Surface)

• Between 30Between 30° and ° and 6060° latitude° latitude– Winds flow from West to EastWinds flow from West to East– They are called the WesterliesThey are called the Westerlies

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Wind Patterns (Surface)Wind Patterns (Surface)

• Between the equator and Between the equator and 3030° ° latitudelatitude– Wind flows from East to WestWind flows from East to West– North of the equator they are called the North of the equator they are called the

Northeast Trade WindsNortheast Trade Winds– South of the equator they are called the South of the equator they are called the

Southeast Trade WindsSoutheast Trade Winds

Jet StreamsJet Streams

• Jet streams are high speed winds in Jet streams are high speed winds in the upper tropospherethe upper troposphere

• They flow from West to East and They flow from West to East and steer the weather like highs and lowssteer the weather like highs and lows

Causes of Prevailing WindCauses of Prevailing Wind

• Solar energies (the ones that make it Solar energies (the ones that make it through the atmosphere) strike close through the atmosphere) strike close to the equator to the equator

• Here, hot air rises and expands Here, hot air rises and expands leaving a leaving a LOWLOW pressure area behind pressure area behind

• When the rising air reaches the When the rising air reaches the tropopausetropopause it moves North it moves North

Causes of Prevailing Winds Causes of Prevailing Winds #2#2• Once the air reaches 30Once the air reaches 30° latitude it has ° latitude it has

become colder and more dense so it become colder and more dense so it sinkssinks– A A HIGHHIGH pressure area is created pressure area is created

• Air at the surface then moves away from Air at the surface then moves away from the the HIGHHIGH pressurepressure towards the LOWLOW at at the equator that was created previouslythe equator that was created previously– As it moves it twists to the rightAs it moves it twists to the right

•THE NORTHEAST TRADE WINDS!!!THE NORTHEAST TRADE WINDS!!!

Causes of Prevailing Winds Causes of Prevailing Winds #3#3• Not all of the air goes back to the Not all of the air goes back to the

equator once it has reached the surfaceequator once it has reached the surface• Some of it is deflected North towards Some of it is deflected North towards

the the LOWLOW pressure area at 60 pressure area at 60° latitude° latitude– Twists to the right and creates the mid-Twists to the right and creates the mid-

latitude Westerlieslatitude Westerlies

• At At 6060° latitude polar air creates a ° latitude polar air creates a LOWLOW when it pushes warmer air up to the jet when it pushes warmer air up to the jet streamstream

Causes of Prevailing Winds Causes of Prevailing Winds #4#4• At the North pole the air is cold and At the North pole the air is cold and

dense so it sinks creating a dense so it sinks creating a HIGHHIGH pressure area at the surfacepressure area at the surface

• Surface air moves South, away from this Surface air moves South, away from this high pressure area high pressure area – It twists to the right creating polar easterliesIt twists to the right creating polar easterlies

• Air rising at the 60Air rising at the 60° latitude can go ° latitude can go North or South once it reaches the North or South once it reaches the tropopausetropopause

Effects of Prevailing WindsEffects of Prevailing Winds

• The high and low pressure areas that The high and low pressure areas that are created by the prevailing winds are created by the prevailing winds allow heat to be transferred throughout allow heat to be transferred throughout the worldthe world

• They also cause precipitation and affect They also cause precipitation and affect the climate of different regionsthe climate of different regions– Rising air is warm and moistRising air is warm and moist– Falling air is cold and dryFalling air is cold and dry

• Can you point out some of the climates?Can you point out some of the climates?

• Prevailing winds and jet streams Prevailing winds and jet streams change with the seasonschange with the seasons– They follow the sun!!They follow the sun!!

• The Northeast trade winds move The Northeast trade winds move south, closer to the equator during south, closer to the equator during the winterthe winter