Model Answer
0 min readIntroduction
Hot deserts are arid regions characterized by high temperatures and low precipitation. A significant number of these deserts are found in the Northern Hemisphere, specifically between 20-30 degrees North latitude, and predominantly on the western margins of continents. This consistent geographical pattern isn’t coincidental; it’s a direct consequence of global atmospheric circulation patterns and the interplay between landmasses and oceanic currents. Understanding these factors is crucial to comprehending the distribution of these harsh environments and their impact on regional climates.
Global Atmospheric Circulation and Hadley Cells
The primary driver of this phenomenon is the Hadley Cell, a major atmospheric circulation system. Solar radiation is strongest at the equator, leading to intense heating and rising air. This rising air cools and releases moisture, resulting in heavy rainfall in the equatorial regions. As the air reaches the upper troposphere, it diverges and travels poleward.
Subtropical High-Pressure Belts
Around 30 degrees North and South latitude, the poleward-moving air begins to descend. This descending air creates areas of high atmospheric pressure, known as subtropical high-pressure belts. Descending air is dry as it suppresses cloud formation and precipitation. This is a fundamental reason for the presence of deserts in these latitudes.
Continental Influence and Western Margins
The western sides of continents are particularly susceptible to desert formation due to the influence of prevailing winds and ocean currents.
- Prevailing Winds: Trade winds, which blow from the subtropical high-pressure belts towards the equator, are dry. When these winds flow over land, they contribute to aridity.
- Cold Ocean Currents: The western coasts of continents in these latitudes are often affected by cold ocean currents (e.g., the Canary Current off the coast of North Africa, the California Current off the coast of California). These currents stabilize the atmosphere, reducing the potential for precipitation. Cold currents also cool the air above them, further inhibiting convection and rainfall.
- Rain Shadow Effect: Mountain ranges running parallel to the western coasts exacerbate the aridity. Moist air from the ocean is forced to rise over the mountains, leading to orographic rainfall on the windward side. By the time the air descends on the leeward side, it is dry, creating a rain shadow desert.
Examples of Major Hot Deserts
Several prominent hot deserts exemplify this pattern:
- Sahara Desert (North Africa): Influenced by the subtropical high-pressure belt and the Canary Current.
- Arabian Desert (Middle East): Located within the subtropical high-pressure belt and experiences dry descending air.
- Sonoran Desert (North America): Affected by the California Current and experiences a rain shadow effect from the Sierra Nevada mountains.
- Australian Deserts (Australia): Located within the subtropical high-pressure belt and influenced by cold currents.
| Desert | Latitude (approx.) | Influencing Factors |
|---|---|---|
| Sahara | 20-30°N | Subtropical High, Canary Current |
| Arabian | 25-30°N | Subtropical High |
| Sonoran | 30-35°N | California Current, Rain Shadow |
Conclusion
In conclusion, the concentration of major hot deserts between 20-30 degrees North latitude and on the western sides of continents is a result of the interplay between global atmospheric circulation, specifically the Hadley Cell and the formation of subtropical high-pressure belts, coupled with the influence of cold ocean currents and, in some cases, the rain shadow effect. These factors combine to create conditions of stable, descending air and limited moisture, fostering the development of arid environments. Understanding these geographical patterns is vital for predicting and mitigating the impacts of desertification and climate change.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.