Wind Coriolis Effect (p. 516) Prevailing Winds (p )

Coriolis Effect The spinning of the Earth creates an effect on any item that is in the air for a long period of time The spinning of the Earth creates an effect on any item that is in the air for a long period of time –Winds are therefore affected Was discovered by Gustave Coriolis when working with the army Was discovered by Gustave Coriolis when working with the army –They couldn’t figure out why their carefully aimed canons weren’t hitting their target

Coriolis Effect In the Northern hemisphere, the rotation is to the East (counterclockwise) In the Northern hemisphere, the rotation is to the East (counterclockwise) –Objects will ‘drift’ to the right In the Southern hemisphere, the rotation is to the West (clockwise) In the Southern hemisphere, the rotation is to the West (clockwise) –Objects will ‘drift’ to the left The Coriolis effect is noticed the least at the equator and the most at the poles The Coriolis effect is noticed the least at the equator and the most at the poles

Winds Some winds are small and regional Some winds are small and regional Many are major wind patterns that cover large areas Many are major wind patterns that cover large areas –These winds are called Prevailing Winds

Wind Patterns (Surface) Between 60° latitude and the poles Between 60° latitude and the poles –Winds move from East to West –They are called the Polar Easterlies W E

Wind Patterns (Surface) Between 30° and 60° latitude Between 30° and 60° latitude –Winds flow from West to East –They are called the Westerlies W E

Wind Patterns (Surface) Between the equator and 30° latitude Between the equator and 30° latitude –Wind flows from East to West –North of the equator they are called the Northeast Trade Winds –South of the equator they are called the Southeast Trade Winds

Jet Streams Jet streams are high speed winds in the upper troposphere Jet streams are high speed winds in the upper troposphere They flow from West to East and steer the weather like highs and lows They flow from West to East and steer the weather like highs and lows

Causes of Prevailing Wind Solar energies (the ones that make it through the atmosphere) strike close to the equator Solar energies (the ones that make it through the atmosphere) strike close to the equator Here, hot air rises and expands leaving a LOW pressure area behind Here, hot air rises and expands leaving a LOW pressure area behind When the rising air reaches the tropopause it moves North When the rising air reaches the tropopause it moves North

Causes of Prevailing Winds #2 Once the air reaches 30° latitude it has become colder and more dense so it sinks Once the air reaches 30° latitude it has become colder and more dense so it sinks –A HIGH pressure area is created Air at the surface then moves away from the HIGHpressureLOW at the equator that was created previously Air at the surface then moves away from the HIGH pressure towards the LOW at the equator that was created previously –As it moves it twists to the right THE NORTHEAST TRADE WINDS!!! THE NORTHEAST TRADE WINDS!!!

Causes of Prevailing Winds #3 Not all of the air goes back to the equator once it has reached the surface Not all of the air goes back to the equator once it has reached the surface Some of it is deflected North towards the LOW pressure area at 60° latitude Some of it is deflected North towards the LOW pressure area at 60° latitude –Twists to the right and creates the mid- latitude Westerlies At 60° latitude polar air creates a LOW when it pushes warmer air up to the jet stream At 60° latitude polar air creates a LOW when it pushes warmer air up to the jet stream

Causes of Prevailing Winds #4 At the North pole the air is cold and dense so it sinks creating a HIGH pressure area at the surface Surface air moves South, away from this high pressure area –I–I–I–It twists to the right creating polar easterlies Air rising at the 60° latitude can go North or South once it reaches the tropopause

Effects of Prevailing Winds The high and low pressure areas that are created by the prevailing winds allow heat to be transferred throughout the world The high and low pressure areas that are created by the prevailing winds allow heat to be transferred throughout the world They also cause precipitation and affect the climate of different regions They also cause precipitation and affect the climate of different regions –Rising air is warm and moist –Falling 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 change with the seasons –T–T–T–They follow the sun!! The Northeast trade winds move south, closer to the equator during the winter