The characteristics, formation and global distribution of tropical storms; their primary and secondary impacts in a named example; and immediate and long-term responses, including how development affects vulnerability.

What this dot point is asking

This is OCR GCSE Geography B (J384) Component 1, Our Natural World, within Global Hazards: "What are the causes and impacts of extreme weather?" For tropical storms, OCR expects you to describe their characteristics and global distribution, explain how they form within the global circulation, and use a named example to describe their primary and secondary impacts and the immediate and long-term responses. A recurring theme is that a country's level of development shapes how badly it is affected.

Characteristics and distribution

A tropical storm is an intense low-pressure system with very strong winds and torrential rain, spiralling around a calm centre called the eye. Around the eye is the eye wall, a ring of towering cloud where the most violent winds and heaviest rain occur. The same hazard has different regional names: hurricanes in the Atlantic and east Pacific, cyclones in the Indian Ocean, and typhoons in the west Pacific. They occur in a belt either side of the Equator, over the warm tropical oceans, in the late summer and autumn of each hemisphere when sea temperatures are highest.

How tropical storms form

Tropical storms need a specific set of conditions, all of which trace back to the global circulation.

Primary and secondary impacts

OCR wants you to separate the two clearly.

• Primary impacts happen immediately and directly from the storm: buildings and infrastructure destroyed by winds, and coastal areas drowned by the storm surge (a wall of seawater pushed ashore by the wind and low pressure). People are killed and injured, and crops are flattened.
• Secondary impacts follow in the hours, days and weeks afterwards: flooding and landslides from the rain, disease spreading through contaminated water, food and water shortages, loss of jobs and income, and the cost of rebuilding.

Responses

Responses are graded by time and by a country's resources.

• Immediate responses aim to save lives: search and rescue, evacuation, emergency shelter, medical care, and emergency aid (food, water, tents). In Typhoon Haiyan, international aid and military support arrived to reach cut-off communities.
• Long-term responses aim to rebuild and reduce future risk: repairing homes, roads and power, restoring the economy, and improving preparedness through better warning systems, sea defences and building codes.

A country's level of development runs through all of this. In a lower-income country such as the Philippines, weakly built homes collapse, warnings may arrive late, and emergency services are stretched, so the death toll is high. In a higher-income country, sturdier buildings, well-rehearsed evacuation and faster recovery reduce the human cost even from a powerful storm.

Try this

Q1. Explain why a tropical storm weakens when it reaches land. [3 marks]

• Cue. It is cut off from its energy source (warm ocean water and moisture), so the rising air and latent heat that power it decline.

Q2. Suggest two immediate responses that could reduce deaths from a tropical storm. [4 marks]

• Cue. Evacuation before landfall and rapid search and rescue with emergency shelter and medical aid afterwards.