Atmospheric circulation, tropical storms and extreme weather in the UK.
Notes and quizzes readyCore topic
Named examples on this page are revision choices. Use your school’s examples if they differ.
Revise the key ideas
Global atmospheric circulation
The Sun heats the equator more strongly than the poles. This uneven heating drives a global circulation system that transfers heat through the atmosphere.
Near the equator, warm moist air rises, creating low pressure. As air rises it cools; water vapour condenses into clouds and frequent heavy rain.
Air moves towards higher latitudes at altitude and sinks around 30° north and south. Descending air warms and becomes relatively dry, producing high pressure and helping explain subtropical desert belts.
The Hadley cells operate between the equator and about 30°, the Ferrel cells between about 30° and 60°, and the Polar cells between about 60° and the poles. These are a simplified average model; their positions change with seasons.Simplified atmospheric pressure belts. Approximate average positions; belts shift seasonally. The model links rising air with low pressure and sinking air with high pressure.
Around 60°, warmer and colder air meet and air tends to rise, giving low pressure and changeable weather. At the poles, cold dense air sinks and creates high pressure.
Surface winds flow broadly from high to low pressure and are deflected by Earth's rotation. Trade winds blow towards the equator, prevailing westerlies affect mid-latitudes, and polar easterlies flow from polar high pressure.
Tropical storm formation and structure
Tropical storms form over warm tropical oceans, usually between about 5° and 30° north and south. They are called hurricanes in the Atlantic and northeast Pacific, typhoons in the northwest Pacific, and cyclones in other basins.
Storm formation needs warm water, typically at least about 26.5°C through a sufficient depth, abundant moisture, a starting disturbance and low vertical wind shear (little change in wind speed or direction with height).
Warm seawater supplies heat and water vapour. Warm moist air rises and condenses; condensation releases heat, encouraging more rising air and lowering surface pressure.
More air flows into the low-pressure centre. Earth's rotation makes the system rotate, and thunderstorms organise around the centre. Rotation is too weak at the equator for tropical cyclones normally to form there.
The eye is a relatively calm central area with descending air. The eyewall around it contains the strongest winds and intense rain; spiral rainbands extend farther out.Eye and eyewall. The central eye is relatively calm. Strong upward motion occurs in the surrounding eyewall; the sketch is not to scale.
A storm strengthens while it has a supply of warm moist air and favourable atmospheric conditions. It weakens over land, cooler water or stronger wind shear because its energy supply or structure is disrupted.
A storm surge is a rise in sea level mainly caused by winds pushing seawater towards land, with low pressure also contributing. Surge, high tide and waves together can cause severe coastal flooding.
Effects, responses and reducing risk
Primary effects include wind damage, storm-surge flooding and river flooding from heavy rain. Deaths, injuries and damage to buildings can occur directly.
Secondary effects include contaminated water, disease risk, disrupted transport, loss of income and food shortages. Flooded farmland or damaged fishing boats can affect livelihoods long after the storm.
Immediate responses include evacuation, rescue, emergency shelter, medical care and food and water. Long-term responses include restoring livelihoods, rebuilding homes and strengthening coastal protection.
Satellites, ocean buoys, radar and aircraft observations help monitor storms. Computer models predict possible tracks and intensity, but forecasts change as new information arrives.
Protection includes storm shelters, strong roofs and coastal defences. Planning includes warnings, evacuation routes, practice drills and keeping new buildings away from areas at highest risk.
A warning only helps if people receive it, understand it and can act on it. Transport, trust, shelter space and accessible communication affect evacuation.
Warmer oceans and a warmer atmosphere can increase tropical cyclone rainfall and the potential intensity of the strongest storms. The proportion of very intense storms is expected to increase, but total global storm frequency is not certain to increase.
Sea-level rise increases coastal flooding risk from storms. Where storms occur can also shift; climate change does not mean every ocean will develop tropical storms.
UK weather hazards and changing extremes
UK hazards include heavy rain and flooding, strong winds, snow and ice, thunderstorms, drought and heatwaves. Their effects depend on duration, intensity, season and local vulnerability.
Flooding can damage homes, transport and farmland. Drought can reduce river flows and water supplies. Heatwaves can increase illness and wildfire risk; snow and ice can interrupt travel and electricity.
The UK has warmed, and extreme heat is becoming more likely. Climate change also increases the potential for heavy rainfall because warmer air can hold more moisture, although rainfall trends vary by season and region.
A single event does not prove a long-term trend. Compare observations over many years and use attribution studies to assess how climate change has altered an event's likelihood or intensity.
For a UK extreme-weather example, explain its atmospheric causes, separate social/economic/environmental effects, then link management actions to the risks they reduce.
Named tropical storm: Typhoon Haiyan, Philippines, 2013
Typhoon Haiyan, known locally as Yolanda, crossed the Philippines on 8 November 2013. Warm western Pacific waters helped support an exceptionally powerful storm, and low-lying coastal settlements were exposed to its winds and surge.
Strong winds destroyed buildings and storm-surge flooding devastated parts of Tacloban and surrounding coastal areas. WHO reports 6,300 deaths and more than 28,000 injuries.
Damaged water supplies and health facilities increased health risks. Loss of homes, fishing boats, crops and businesses disrupted livelihoods, while damaged transport and communication delayed assistance.
Immediate responses included rescue, food, clean water, temporary shelter and medical care. Philippine authorities and international agencies worked together; WHO helped coordinate emergency medical teams and supplies.
Longer-term recovery included rebuilding health services, housing and livelihoods, alongside efforts to improve warning, evacuation and safer construction. Moving housing away from exposed coasts can reduce risk but may separate people from work.
Haiyan shows why predicting a storm is only one part of protection. People also need to understand surge warnings and reach shelters that are safe from wind and flooding.
Recent UK example: July 2022 extreme heat
During 16–19 July 2022, very hot air moved north from continental Europe and strong sunshine intensified the heat. On 19 July, Coningsby in Lincolnshire recorded 40.3°C, the UK's first recorded temperature above 40°C.
Social impacts included heat illness and extra pressure on health services. Older people, people with existing health conditions and those unable to cool their homes were especially vulnerable.
Transport and working conditions were affected: high temperatures can buckle rails and damage road surfaces, causing delays and extra costs. Businesses and schools had to adapt activities and protect people from heat.
Dry vegetation and extreme heat increased fire risk. Fires damaged homes and habitats, while low water availability and heat stress affected wildlife. Separate the July event from longer-lasting drought conditions that developed during the summer.
Warnings, health advice, checking vulnerable people and changing work or travel plans reduced exposure. Shading, cool spaces, water access and longer-term building adaptations can reduce future risk.
Human-caused warming made such exceptional UK heat much more likely. A record temperature provides event evidence, while long-term temperature observations establish the wider trend.
Test yourself
50 questions · Random sets of 10. These quick checks support revision; practise longer explanations and justified judgements too.
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