Weather Hazards and Atmospheric Systems

Atmospheric hazards — tropical storms, tornadoes, heatwaves, blizzards and other extreme weather events — affect more people globally than tectonic hazards. Understanding why they occur requires knowledge of the global atmospheric circulation, energy transfer mechanisms and the role of the jet stream. This lesson establishes the atmospheric science foundations that underpin all weather hazard topics in the AQA specification.

---

The Global Atmospheric Circulation

The atmosphere is a giant heat engine. The fundamental driver of atmospheric circulation is the unequal heating of the Earth's surface by solar radiation:

• The tropics receive more incoming solar radiation (insolation) than they emit as outgoing longwave radiation — they have a radiation surplus
• The poles receive less insolation than they emit — they have a radiation deficit
• This imbalance creates a temperature gradient that drives the atmospheric (and oceanic) circulation, transferring heat from the equator to the poles

The Three-Cell Model

The global atmospheric circulation is conventionally described using the three-cell model, first conceptualised by George Hadley (1735), William Ferrel (1856) and others: