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Difficulty: MediumClimatic Controls and World Climate Types

Which global atmospheric mechanism is primarily responsible for the extreme aridity observed in world trade wind deserts located around latitudes 20∘20^\circ to 30∘30^\circ North and South, such as the Sahara and the Australian Desert?

  1. Subtropical high-pressure belt subsidence causing air to warm adiabatically and suppress cloud formationAnswer
  2. B
    Equatorial low-pressure convergence generating strong vertical convection and rain-shadow effects
  3. C
    Poleward displacement of warm ocean currents reducing evaporation rates over coastal margins
  4. D
    Continuous uplift of moist air along maritime polar fronts driven by prevailing westerly winds

Answer

Subtropical high-pressure belt subsidence causing air to warm adiabatically and suppress cloud formation
The correct answer highlights that global trade wind deserts lie under the subtropical high-pressure belts (Horse Latitudes). In these belts, descending air contracts and heats adiabatically, reducing relative humidity and preventing the formation of precipitation-producing clouds.

Step-by-Step Solution

1
Identify the geographical location of trade wind deserts
Trade wind deserts (such as the Sahara and Australian Deserts) lie in the subtropical zone between 20∘20^\circ and 30∘30^\circ latitude in both hemispheres.
Determining latitude pinpoints the dominant pressure cell and atmospheric circulation mechanism.
2
Analyze atmospheric circulation in subtropical belts
Air that rises at the Equator moves poleward in the upper troposphere and sinks (subsides) around 30∘30^\circ latitude within the Subtropical High-Pressure cells.
Subsiding air undergoes adiabatic compression, which increases temperature and lowers relative humidity, preventing cloud development.

Key Concept

Subtropical High-Pressure Subsidence as a Climatic Control
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Topics

Climatic Controls and World Climate Types

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