The atmospheric pressure is uniform between certain latitudes. Based on that the earth’s surface is divided into different pressure belts. These are known as global pressure belts.
Equatorial low pressure belt: This pressure belt extends upto 5°N and 5°S of the equator. This is the zone where the sun’s rays fall vertically throughout the year. Hence the temperature will be high in this zone all through the year. The air expands due to sun’s heat and ascends on a massive scale. This is the reason for the formation of low pressure here. As the air in this zone ascends on a large scale, winds are feeble here. This pressure belt is also known as Doldrum, meaning the zone with no winds.
Subtropical high pressure belts: Subtropical high pressure belts extend about 30°N and 30°S. The hot air ascending from the equatorial low pressure belt cools gradually and subsides at the subtropical zone due to the rotation of the earth. This is the reason for the formation of high pressure belts all along this zone. These latitudes are also known as horse latitudes.
Subpolar low pressure belts: The pressure belts formed over 60°N and 60°S are the subpolar low pressure belts. As this zone is close to the poles, the air is colder here. Though the cold air remains closer to earth, the air is thrown up due to the rotation of the earth. As a result, low pressure is experienced all along the subpolar region.
olar high pressure belts: These zones experience severe cold throughout the year. As a result, the air remains chilled under the extreme cold that prevails over the poles. This contributes to the steady high pressure experienced here.
