Hazardous Earth: Impact of Tropical Cyclones

What are tropical cyclones?
Large-scale rotating storms that form over the oceans in tropical areas.
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What are types of tropical cyclones?
Hurricanes, cyclones and typhoons.
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Where are hurricanes formed?
Between the tropic of cancer and capricorn, in the North Atlantic/ East Pacific ocean.
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Where are typhoons formed?
Between the tropic of cancer and capricorn, in the Pacific Ocean.
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Where are cyclones formed?
Between the tropic of cancer and capricorn, in the Indian Ocean.
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How are tropical cyclones formed?
High temperature causes air to rise away from ocean surface. Rising air causes storms. Converging storms (when they group together) form rapidly rising hot air (wind). This results in low pressure on the centre of storms.
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What 4 conditions do storms need to become tropical cyclones?
Warm, moist air (above 26.5°c); time of year when ocean is warmest (Jun-Nov-- Northern tropics, Apr-Nov-- Southern tropics); winds converging at ocean surface; location 5-30° N/S for Coriolis Effect.
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What is the eye of the storm?
The centre of the tropical cyclone, where air is falling back to the surface- no wind and clear skies.
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What is the eye wall?
Area around the eye, where there is the strongest wind and heaviest rain.
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Why does a tropical cyclone need high humidity?
So water in the atmosphere can cool rapidly to make air condense and lead to low pressure conditions.
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Why does a tropical cyclone need a low wind shear, and what is it?
When all wind is travelling in the same direction. Without a low wind shear, the centre of the storm will weaken so the air can't rise, which is needed to form a tropical cyclone.
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What is the Coriolis Effect?
It causes fluids to curve across or above the Earth's surface.
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Explain what happens to a tropical cyclone due to the Coriolis Effect?
Air rushes from areas of high to low pressure. These rushing winds are deflected into a spin by the rotation of the Earth.
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Which direction do tropical cyclones in the Northern Hemisphere spin?
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Which direction do tropical cyclones in the Southern Hemisphere spin?
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What is the source area?
The area where a tropical cyclone is formed.
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Where do tropical cyclones move (compared to the source area)?
Away from the source area and following the direction of the prevailing wind and ocean current.
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What is the track?
The path that the cyclone takes.
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Where are tropical cyclones most likely to occur?
In the Inter-tropical Convergence Zone.
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What is the ITCZ?
Inter-Tropical Convergence Zone: an area of permanently low air pressure around the Equator.
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Where does the ITCZ move at certain point of the year?
South in the Southern Hemisphere's summer and North in the Northern Hemisphere's summer.
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Why are tropical cyclones more intense when there is warmer water?
Tropical cyclones are powered by the heat energy released when warm, moist air condenses (the energy pushes air up into the upper atmosphere).
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What is dissipation?
Losing energy.
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Why does a tropical cyclone dissipate?
It reaches land (loses its source of fuel-water); moves into areas of colder water (below 26.5°c); runs into areas where winds are blowing in different directions.
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What is the most reliable indicator of damage a tropical cyclone will cause?
Wind speed.
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What does the Saffir-Simpson Scale do?
Categorises tropical cyclones based on wind speed and likely damage to property/the environment.
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What are the 4 hazards of tropical cyclones?
Strong winds; storm surges (high tides are higher than usual due to low air pressure- there is less weight on the ocean); intense rainfall (can get 1000mm+); landslides (ground becomes saturated, making it heavier, which causes it to slump).
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What are the 4 types of vulnerability?
Physical, Relief, Social, Economic.
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What is the physical vulnerability?
Coastal areas at greater risk because tropical cyclones form over water.
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What is the relief vulnerability?
Low lying areas at risk because flooding is more likely (wind, rain, storm surges). High relief areas likely to have heavy rain and therefore more at risk of landslides.
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What is the social vulnerability? (1)
Areas of poverty at risk: construction standards lower, so will be more easily damaged. After effects felt more there as people may not have access to food, clean water, shelter, medical care.
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What is the social vulnerability (2)?
Older/younger people more likely to be injured as they may have more difficulty evacuating. More at risk to disease especially with a limited supply to water.
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What is the economic vulnerability?
Poorer, less developed countries (LIC) have to wait for international: aid, food, water, medicine and temporary shelters.
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What are more developed countries more likely to have?
Access to weather prediction to prepare for the storm, coastal defences against storm surges, evacuation procedures and disaster response teams.
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How can a tropical cyclone cause a storm surge?
Low air pressure (needed to form a tropical cyclone) lifts weight off the ocean. This causes it to rise and makes high tides higher than usual.
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What are the forecasting methods?
Atmospheric pressure, satellite tracking, radar, modelling.
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What does atmospheric pressure do?
Gives the earliest information on a potential tropical cyclone.
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How do you measure atmospheric pressure?
Anchor buoys into oceans/ships and send the recorded readings/data back to shore. Or fly special planes through the upper layers of the tropical cyclone to help forecast.
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What does satellite tracking do?
Views large areas of the ocean to track the formation of tropical cyclones (can be mistaken for cirrus cloud canopy system).
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What does RADAR do?
Identifies large banks of precipitation from a large distance away -- expensive.
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What is modelling?
Where computer systems model information on the tropical cyclones, like: the likely track of the storm, it's intensity, when it's likely to dissipate.
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What can the government do in a tropical cyclone?
Activate flood defences, order evacuations, prepare emergency services.
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What ways do people respond to a tropical cyclone?
Trained rescue teams search for people trapped in collapsed buildings. Provide food, clean water, shelter, medicine care to prevent death from malnutrition, disease, injury. Restore/reconstruct area by clearing roads, restoring power, drinking water.
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When and where did Hurricane Katrina occur?
August 2005, in New Orleans, on the Southern coast of the USA on the gulf of Mexico.
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