Global Atmospheric Circulation

Understanding global atmospheric circulation is essential for explaining why different parts of the world experience different weather patterns, and why tropical storms form where they do. This lesson covers the three-cell model, pressure belts, and surface winds — all key components of the AQA GCSE specification.

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Why Does the Atmosphere Circulate?

The atmosphere circulates because of unequal heating of the Earth's surface by the Sun:

• At the equator, the Sun's rays hit the Earth at a high angle (close to 90 degrees), concentrating energy over a small area. This means the equator receives more heat per unit area.
• At the poles, the Sun's rays hit at a low angle, spreading energy over a larger area. The poles receive less heat per unit area.
• The atmosphere and oceans redistribute this heat from the equator towards the poles through circulation cells and ocean currents.

The Role of the Coriolis Effect

The Coriolis effect is caused by the Earth's rotation: