Pressure Belts of the Earth
There is a systematic pattern of alternate high and low pressure belts over the surface of the Earth. It is established that, there are altogether seven such Pressure Belts and certain natural factors are responsible for their creation. These seven identified Pressure Belts on the Earth’s surface are geographically named as, the Equatorial Low, the two Sub-Tropical highs, the two Sub-polar or Temperate lows and the two Polar highs. It is evident that, except the Equatorial low, the others form matching pairs in the Northern and Southern Hemispheres.
As the shape of the Earth is spherical, all the parts of the Earth are not heated uniformly. The Equatorial region receives a great amount of heat throughout the year and as a result, the warm air at the Equator being light, rises up and creates a low pressure. On the other hand, at the poles the cold heavy air causes high pressure.
Apart from the shape of the earth, the rotation of the earth also plays an important role in it. The rotation of the earth pushes up the bulk of the air towards the Equator, creating a low pressure belt in the Sub- Polar Regions, situated around latitudes 60° to 65° North and South of the Equator and the cold heavy air causes high pressure.
In general, the distribution of pressure portrays a good indication of the Prevailing winds. However, these belts are not necessarily continuous, since the surface of the Earth consists of both land and sea and there is unequal distribution of the heat received from the rays of the Sun. Apart from that, as it is mentioned previously, the rotation of the Earth also has its effects on them.