Transcript Wind
Wind Coriolis Effect (p. 516) Prevailing Winds (p. 516-519) Coriolis Effect • 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 – 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) – Objects will ‘drift’ to the right • 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 Winds • Some winds are small and regional • Many are major wind patterns that cover large areas – These winds are called Prevailing Winds Wind Patterns (Surface) • 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 – Winds flow from West to East – They are called the Westerlies W E Wind Patterns (Surface) • 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 • 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 • Here, hot air rises and expands leaving a LOW pressure area behind • 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 – A HIGH pressure area is created • 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!!! Causes of Prevailing Winds #3 • 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 – Twists to the right and creates the midlatitude Westerlies • 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 – 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 • 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? • Prevailing winds and jet streams change with the seasons – They follow the sun!! • The Northeast trade winds move south, closer to the equator during the winter