Vertical Distribution

  • Air is a mixture of various gases.
  • It is highly compressible. As it compresses, its density increases.
  • The higher the density of air, the greater is the air pressure and vice versa.
  • The mass of air above in the column of air compresses the air under it hence its lower layers are more dense than the upper layers. As a result, the lower layers of the atmosphere have higher density, hence, exert more pressure.
  • Conversely, the higher layers are less compressed and, hence, they have low density and low pressure.
  • The columnar distribution of atmospheric pressure is known as vertical distribution of pressure.
  • Air pressure decreases with increase in altitude but it does not always decrease at the same rate.
  • Dense components of atmosphere are found in its lowest parts near the mean sea level.
  • Temperature of the air, amount of water vapour present in the air and gravitational pull of the earth determine the air pressure of a given place and at a given time.
  • Since these factors are variable with change in height, there is a variation in the rate of decrease in air pressure with increase in altitude.
  • The normal rate of decrease in air pressure is 34 millibars per every 300 metres increase in altitude.
  • The effects of low pressure are more clearly experienced by the people living in the hilly areas as compared to those who live in plains.
  • In high mountainous areas rice takes more time to cook because low pressure reduces the boiling point of water.
  • Breathing problem such as faintness and nose bleedings are also faced by many trekkers from outside in such areas because of low pressure conditions in which the air is thin and it has low amount of oxygen content.