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Difficulty: HardClimatic Controls and World Climate Types

During the Northern Hemisphere winter (low-sun season), the southward migration of the thermal equator causes global wind and pressure belts to shift equatorward. Which climatic condition directly occurs over tropical savanna regions (AwAw) in the Northern Hemisphere as a consequence of this seasonal pressure belt displacement?

  1. Dominance of dry continental tropical air masses and Northeast Trade Winds, resulting in a pronounced dry season.Answer
  2. B
    Intense convective heating and daily squall-line thunderstorms driven by maritime equatorial air masses.
  3. C
    Persistent mid-latitude frontal depression activity bringing uniform year-round precipitation.
  4. D
    Upwelling of cold oceanic water along eastern continental margins generating persistent coastal fogs.

Answer

Dominance of dry continental tropical air masses and Northeast Trade Winds, resulting in a pronounced dry season.
Tropical Savanna (AwAw) climates feature distinct wet and dry seasons driven by the annual oscillation of global wind and pressure belts. During the Northern Hemisphere winter, the solar equator shifts south, causing the Inter-Tropical Convergence Zone (ITCZ) to retreat southward. As a result, subtropical high-pressure ridges expand over tropical savanna regions, bringing stable, descending continental tropical air masses and dry Northeast Trade Winds (the Harmattan), which create the dry season.

Step-by-Step Solution

1
Identify the geographical region and seasonal shift described in the stem.
The target region is the Northern Hemisphere tropical savanna (AwAw), and the event is the low-sun (winter) seasonal shift of pressure belts equatorward.
Climatic controls in tropical regions are primarily governed by the seasonal migration of the thermal equator and the Inter-Tropical Convergence Zone (ITCZ).
2
Analyze atmospheric circulation patterns during Northern Hemisphere winter.
The ITCZ moves south toward the equator, bringing the Subtropical High-Pressure Belt and continental tropical (cTcT) air masses southwards over the savanna belt.
Descending air within subtropical high-pressure zones creates stable, dry atmospheric conditions.
3
Determine the prevailing wind system and resulting weather.
The dry Northeast Trade Winds (Harmattan in West Africa) sweep across the savanna, causing a marked dry season.
Outflowing winds from continental interior high-pressure cells carry minimal moisture.

Key Concept

Seasonal migration of global pressure belts and ITCZ as climatic controls for Tropical Savanna (AwAw) climate seasonality.
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Topics

Climatic Controls and World Climate Types

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