4.2 Global Wind Patterns

Unequal heating drives wind

The sun heats Earth unevenly — the equator gets more direct radiation than the poles. This creates temperature and pressure differences that drive convection currents in the atmosphere, forming large-scale circulation cells (like Hadley cells) that move air, heat, and moisture from the equator toward the poles, creating global wind patterns.

The Coriolis effect bends wind

Earth's rotation causes the Coriolis effect, deflecting moving air to the right in the Northern Hemisphere and left in the Southern Hemisphere. This bending combines with convection cells to create prevailing winds like the trade winds, westerlies, and polar easterlies, which influence climate zones and weather patterns worldwide.

Winds shape climate and resources

Global wind patterns influence precipitation distribution, ocean currents, and desert locations. Rising air near the equator cools and releases moisture (tropical rainforests), while descending dry air around 30° latitude creates deserts. These patterns affect agriculture, water availability, and the spread of pollutants across regions.

Key terms

Coriolis effect

Deflection of moving air (and water) caused by Earth's rotation — right in the Northern Hemisphere, left in the Southern Hemisphere.

Hadley cell

Atmospheric circulation cell between the equator and 30° latitude; warm air rises at the equator and sinks at 30°.

Trade winds

Steady winds blowing from east to west near the equator, part of the Hadley cell circulation.

Westerlies

Prevailing winds blowing from west to east in the mid-latitudes (about 30°–60°).

Why deserts form near 30° latitude

Descending, dry air from Hadley cell circulation creates high pressure and low precipitation, forming desert climates.

Try an AP-style question

Why do many of the world's deserts lie near 30° latitude?

1. Strong polar winds
2. Descending dry air from Hadley cells
3. Constant ocean upwelling
4. Rising moist air at those latitudes