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Factors Controlling Temperature Distribution
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- Latitude
- Altitude
- Distance from the sea
- Air mass and ocean currents
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Inversion Of Temperature
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- When the temperature decreases with an increase in elevation are called the normal lapse rate. At times, the situation is reserved and the normal lapse rate is inverted. It is called inversion of temperature. Eg. Sea breeze, land breeze, Fog, etc.
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Atmospheric Pressure
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- The weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere is called atmospheric pressure.
- In the lower atmosphere, the pressure decreases rapidly with height.
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Force Affecting The Velocity And Direction Of The Wind
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- The air in motion is called wind. The wind blows from high pressure to low pressure. Forces – Gravitational force, Friction force, Pressure Gradient force, Coriolis Force.
- The force exerted by the rotation of the earth is known as the Coriolis force.
- The wind circulation around a low pressure is called cyclonic circulation. Around high pressure, it is called anticyclonic circulation.
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General Circulation Of The Atmosphere
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It depends on the –
- Latitudinal variation of atmospheric heating
- The emergence of pressure belts
- The migration of belts following the apparent path of the sun
- The distribution of continents and oceans
- The rotation of the earth
The pattern of the movement of the planetary winds is called the general circulation of the atmosphere.
- The air at the Inter-Tropical Convergence Zone (ITCZ), which lies near the equator, rises due to the heating caused by the reflected radiation from the surface thus creating low pressure.
- The winds from the tropics (i.e. region around the Tropic of Cancer and Capricorn) flow from their positions towards this low-pressure area. As the air from the tropics reaches the convergence zone it begins to rise because of heating. It reaches an altitude of 14 km and then starts to move towards the poles thus creating the upper air circulation or upper atmospheric circulation.
- While travelling towards the poles, as the air of the upper air circulation gets cold and dense, there is accumulation around 30° N and S latitudes. Some part of the cold air sinks towards the ground creating a subtropical high.
- As it reaches the surface, the wind again starts moving towards the ITCZ near the equator and becomes known as easterlies. This cycle of air circulation in between the Equator and the Tropics is known as the Hadley Cell.
- The cycle of the air in between the mid-latitudes (i.e. around the tropics) and the poles is known as the mid-latitude cell or Ferrel cell. In this case, the rising warmer air) is coming from the subtropical high and the sinking cool air is coming from the poles. Such winds near the surface are known as
- The cycle of air circulation in-between the poles and the mid-latitudes is known as the Polar cell.
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