GA Notes:”PRESSURE BELT (The horizontal distribution of air pressure)” For Railway & SSC Exams 2018-19

Dear Students,

General awareness is an important section that can help you get the maximum time You need not perform complex calculation to settle for the correct option so, it is the best to be ready with the facts and figures in advance. For Railway Group-D Exam 2018, important awards, current affairs, history, geography, general science, economy and static GK is the main part.  To let you have an information about all important sections of GA, this post is to provide you with one of the important topics related to PRESSURE BELT (The horizontal distribution of air pressure). Grab the below given important points related to this particular topic. 

PRESSURE BELT 

(The horizontal distribution of air pressure)

The horizontal distribution of air pressure across the latitudes is characterised by high or low pressure belts.

These pressure belts are: 
(1) The Equatorial Low-Pressure Belt 
(2) The Subtropic High Pressure Belts 
(3) The Sub-polar Low-Pressure Betts 
(4) The Polar High-Pressure Belts


The Equatorial Low-Pressure Belt:

  • The sun shines almost vertically on the equator throughout the year. 
  • As a result, the air gets warm and rises over the equatorial region and produce equatorial low pressure. 
  • This belt extends from equator to 100N and 100S latitudes. 
  • Due to excessive heating horizontal movement of air is absent here and only conventional currents are there. 
  • Therefore this belt is called doldrums (the zone of calm) due to virtual absence of surface winds. 
  • These are the regions of convergence because the winds flowing from sub-tropical high-pressure belts converge here. 
  • This belt is also known as-Inter Tropical Convergence Zone (ITCZ).




The Sub-tropical High-Pressure Belts:

  • The sub-tropical high-pressure belts extend from the tropics to about 35° latitudes in both the Hemispheres. 
  • In the northern hemisphere it is called as the North sub-tropical high-pressure belt and in the southern hemisphere it is known as the South sub-tropical high pressure belt.
  • In olden days vessels with cargo of horses passing through these belts found difficulty in sailing under these calm conditions. 
  • They used to throw the horses in the sea in order to make the vessels lighter. 
  • Henceforth these belts or latitudes are also called ‘horse latitudes’. 
  • These are the regions of divergence because winds from these areas blow towards equatorial and subpolar low-pressure belts.



The Sub-polar low-Pressure Belts:

  • The sub-polar low-pressure belts extend between 45°N and the Arctic Circle in the northern hemisphere and between 45°S and the Antarctic Circle in the southern hemisphere. 
  • They are known as the North sub-polar low and the South sub-polar low-pressure belts respectively. 
  • Winds coming from the sub-tropical and the polar high belts converge here to produce cyclonic storms or low-pressure conditions. 
  • This zone of convergence is also known as polar front.  



The Polar High-Pressure Belts:

  • In polar regions, sun never shines vertically. 
  • Sun rays are always slanting here resulting in low temperatures. 
  • Because of low temperature, air compresses and its density increases. Hence, high pressure is found here. 
  • In northern hemisphere the belt is called the North polar high-pressure belt while it is known as the South polar high pressure belt in the southern hemisphere. 
  • Winds from these belts blow towards sub-polar low pressure belts.



Note:
Pressure belts also shift northwards and southwards with the shift of thermal equator (commonly known as the belt of highest temperature). 

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