Answer:

Introduction

Deserts are regions characterized by an annual precipitation of less than 25 centimeters, resulting in exceedingly arid environments. They cover more than one-fifth of the Earth’s land area and are found on every continent. However, major hot deserts, including the Thar Desert, Sahara Desert, and Arabian Desert, are primarily situated along the western coasts of continents in the Northern Hemisphere, particularly in latitudes between 20° and 30°, owing to the following reasons:

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Reasons behind the Geographical Location of Major Hot Deserts:

• Trade Wind Patterns: Trade winds, laden with moisture, deposit their moisture on the eastern portions of continents. By the time these winds reach the western margins, they have become dry, contributing to the arid conditions and desert formation in western regions of continents. Development of the Sahara Desert serves as an example.
• High-Pressure Zone: The hot desert regions are influenced by the subtropical high-pressure belt, where equatorial air currents ascend and then descend. Consequently, these areas experience elevated atmospheric pressure. These high-pressure systems create stable atmospheric conditions that impede the upward movement of moist air. This, in turn, leads to reduced precipitation and the development of arid conditions in these regions.
  • The Sonoran Desert (North America) exemplifies this influence of subtropical high-pressure systems.
• Cold Ocean Currents: Cold ocean currents prevail along the fringes of nearly all tropical deserts. These currents, by cooling the nearby land, hinder the formation of moist, warm air masses, thereby fostering conditions suitable for desert development. The presence of the cold California Current has played a role in the formation of the Arizona and Sonoran Deserts.
• Rain Shadow Effect: Mountain ranges often run parallel to the western coasts of continents. As moist air from the ocean is compelled to ascend over these mountains, it cools and releases moisture, leading to heightened precipitation on the windward side (facing the ocean) and the formation of a rain shadow effect on the leeward side (facing away from the ocean), resulting in arid or desert-like conditions. 
• • For example, the Thar Desert in India has developed due to the presence of a rain-shadow zone created by the parallel Aravalli mountains in the region.
• Subtropical Jet Stream: These regions are influenced by the subtropical jet stream’s trough, resulting in the formation of anticyclonic conditions. This leads to the descent of air, compression, and subsequent warming, which in turn causes a continuous decrease in moisture content, ultimately contributing to desert formation. The formation of the Mojave Desert in the western part of North America serves as an example.

Conclusion

Delving into the factors that influence the positioning of major hot deserts not only illuminates their unique formation but also provides valuable insights into the current expansion of arid regions. By recognizing these crucial connections, we can pave the way for informed strategies to address the pressing challenges posed by desertification and its far-reaching impacts on our environment and societies.