Major hot deserts are located between 20-30 degrees latitudes and on the western side of the continents. Why?

hot deserts

Question- Major hot deserts are located between 20-30 degrees latitudes and on the western side of the continents. Why? (UPSC Mains Previous Year Question)

 Structure of the Answer

  1. Introduction- Define: What is a hot desert?
  2. Main Body- Explain: Why major hot deserts are located between 20-30 degrees latitudes and the western side of the continents? Explain the role of Ocean Currents and give suitable examples.
  3. Conclusion- Conclude on a lighter note.

Model Answer

Introduction

A hot desert is a part of the world that has high average temperatures and very low precipitation. To be classified under this category, these areas need to have less than 250mm or 25cm of rainfall per year. 

world deserts distribution

Body

  • The reasons for aridity of the hot deserts are mainly the effects of off-shore Trade Winds, hence they are also called Trade Wind Deserts.
  • The major hot deserts of the world are located on the western coasts of continents between latitudes 15° and 30°N and S.
  • The biggest desert, Sahara Desert (3.5 million square miles) is also one of the hot deserts. The next biggest desert is the Great Australian Desert. 
  • The other hot deserts are the Arabian Desert, Iranian Desert, Thar Desert, Kalahari, and Namib Deserts.

distribution of hot deserts

  • The hot deserts lie along the Horse Latitudes or the Sub-Tropical High-Pressure Belts where the air is descending, a condition least favorable for precipitation of any kind to take place.
  • The rain-bearing Trade Winds blow off-shore and the Westerlies that are on-shore blow outside the desert limits. 
  • Whatever winds reach the deserts blow from cooler to warmer regions, and their relative humidity is lowered, making condensation almost impossible.
  • There is scarcely any cloud in the continuous blue sky. The relative humidity is extremely low, decreasing from 60 percent in coastal districts to less than 30 percent in the desert interiors. Under such conditions, every bit of moisture is evaporated and the deserts are thus regions of permanent drought. Also, Precipitation is both scarce and most unreliable.
  • On the western coasts, the presence of cold currents gives rise to mists and fogs by chilling the on-coming air. This air is later warmed by contact with the hot land, and little rainfalls.
  • The desiccating effect of the cold Peruvian Current along the Chilean coast is so pronounced that the mean annual rainfall for the Atacama Desert is not more than 1.3 cm.
  • So, all these factors contribute towards the creation of various hot deserts in various parts of the world.
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Conclusion

Therefore, we can see that cold ocean currents play a very important role in the formation of hot deserts along the western coast of the continents and in between 20-30 degrees latitude.

 

Read More about Ocean Currents HERE