Air Pressure and Winds

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  • Created by: remy
  • Created on: 21-08-12 07:09
  • What is Air ?
  • Air is a mixture of several gases present in the atmosphere and it has its own weight.
  • What is meant by Atmospheric pressure?
  • Atmospheric pressure is the pressure at any point on the surface of the earth due to the weight of the column of air above that point.
  • Name the factor on which changes in weather depends, and changes in air density?
  • Changes in  weather depends on air pressure, while changes in air density depends on  temperature
  • What is wind?
  • The variation in pressure causes horizontal movement of air. This horizontal variation in pressure is called wind. Wind transports heat and moisture.
  • Why does air pressure vary from place to place?
  • Air pressure varies from place to place because of the variations in temperature. At sea level air pressure decreases and the temperature increases.
  • Name  the factors affecting Air pressure.
    • Altitude: A we  go higher the air pressure decreases. Air is compressible. Earth gravity pulls the molecules of air downwards. As we go higher these molecules move apart due to lesser gravity and heat absorption is less.
    • Temperature: Air pressure decrease with increase in temperature. When temperature rises air expands as the molecules of air move apart and exert less pressure.
    • Water vapour: Moist air exerts less pressure than dry air because moist air is lighter than dry air and water vapour displaces equal amount of dry air (nitrogen and hydrogen). Therefore a given volume of humid air contains comparatively less amount of oxygen and nitrogen. Hence exerts less pressure.
  • What are the Effects of Air pressure?
  •  Winds are caused :
    •  Warm air being lighter rises up and low pressure is created.
    • Cold air sinks and high pressure is created.
    • Since the atmosphere constantly works to  restore a balance, air moves in from a area of high pressure to low pressure.
    •  This movement of air is known as wind.
  • Influences weather conditions:
    • Upward movement and downward movement of air creates cloudy or clear skies.
    • When air rises it create an area of low pressure, water vapour in the air condenses and formed clouds.
    • Therefore low pressure is associated with cloudy or wet conditions,
    • high pressure indicates clear skies, sunny weather or dry weather.
  •  Weather forecasting:
    • Fluctions in air pressure indicate weather conditions.
  • Name the major pressure belts of the earth.
    • Equatorial low pressure belt
    • Sub tropical high pressure belt
    • sub polar low pressure belt
    • Polar high pressure belts
  • What are the factors responsible for the majorpressure belts of the earth?
    • We have major pressure belts on this earth as
    • Unequal heating of the earth and temperature
    • Rotation of the earth
  • Write a short note on Equatorial Low pressure Belt (Doldrum)
  • Low pressure prevails at the  Equatorial Low pressure Belt  due to
    • Intense Heating
    • High water vapour content in the air reduces the density of the air
    • Earths rate of rotation is maximum at the equator (centrifugal force) which pushes the air away / deflects and causes low pressure
    • Note : The…


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