The formation, distribution and structure of tropical cyclones; their physical hazards and impacts on people; why some countries are more vulnerable; and how preparation and response differ between a developed and a developing or emerging country.

What this dot point is asking

This is Edexcel GCSE Geography B (1GB0) Paper 1, Section A (Topic 1, Hazardous Earth). Edexcel expects you to describe the characteristics, structure and global distribution of tropical cyclones (hurricanes and typhoons); explain how the global atmospheric circulation produces them and why some intensify and others dissipate; describe their physical hazards and impacts on people; explain why some countries are more vulnerable physically, socially and economically; and compare how a developed country and a developing or emerging country prepare for and respond to them. Storm data and tracks often appear, so data and GIS skills are tested too.

Formation and distribution

Tropical cyclones form only where specific conditions combine, which is why they appear in particular places and seasons.

The global atmospheric circulation supplies the rising air near the Equator that triggers them. A cyclone intensifies while it sits over warm water with low wind shear, drawing up more energy. It dissipates when it moves over cooler water or onto land, because its warm-water energy supply is cut off and friction with the land slows it.

Structure and hazards

A mature tropical cyclone has a clear structure. At the centre is the eye, a zone of calm, clear, sinking air about 30 to 50 km across. Around it is the eyewall, a ring of towering cumulonimbus cloud where the winds are strongest and the rainfall heaviest. Spiralling out from the eyewall are bands of rain and wind that weaken with distance.

Vulnerability and management

The same-strength storm can have very different impacts depending on the country it hits.

Countries are more vulnerable for physical reasons (low-lying coasts and large river deltas flood easily, as in Bangladesh), social reasons (dense populations, weak buildings, limited education about warnings) and economic reasons (less money for defences, forecasting, evacuation and recovery). This is why a developing or emerging country often suffers far higher death tolls than a developed country hit by a similar storm.

Management differs accordingly. Preparation and response in a developed country (for example the USA) relies on accurate weather forecasting and satellite tracking, clear warning and evacuation systems, building codes, and well-funded emergency services. A developing or emerging country (for example the Philippines during Typhoon Haiyan in 2013, which killed over 6,000 people and displaced millions) may have warnings but struggle to evacuate dense populations, lacks storm-resistant housing, and depends partly on international aid for relief and recovery.

Try this

Q1. Explain why a tropical cyclone weakens when it moves over land. [4 marks]

• Cue. The storm loses its warm-ocean energy and moisture supply, and friction with the land surface slows the winds, so it weakens and dissipates.

Q2. Explain one reason a developing country may be more vulnerable to a tropical cyclone than a developed country. [2 marks]

• Cue. Less money for sea defences, forecasting and evacuation, weaker buildings, or dense populations on low-lying coastal land, so more people are killed or made homeless.