Storm hazards Flashcards
(31 cards)
What are the conditions for the formation of a tropical storm
- A disturbance near the sea surface e.g. area of low pressure
- Warm sea water above 27 degrees to 50m below surface
- Convergence of air in lower atmosphere which forces warm air to rise
- Location atleast 5 degrees from equator so coriolis effect is strong enough for storm to spin
Give the steps of formation of a tropical storm
- Warm, moist air rises off the warm ocean
- A central vortex starts to develop as more air is drawn in
- As the air continues to rise it cools and condenses to form large rain clouds
- When condensation occurs, latent heat is released which powers the storm
- As the storm continues to grow, the prevailing wind pushes it across the ocean
- Upon reaching land, the supply of moisture and energy is cut off so the storm starts to decay (slow down)
What are the 3 types of tropical storm ?
- Hurricanes (north Atlantic)
- Cyclones (Indian ocean)
- Typhoons (Pacific ocean)
Describe features of tropical storms
- [Intense low pressure system with wind speeds exceeding 75mph]
- Form in the tropics as warm water exists there which rises and condenses which releases energy that increases wind speed
- Lose strength when they move over land as supply of warm moist air is cut off
- Move away from equator due to coriolis effect
- Circular in shape
- Spin anticlockwise in northern hemisphere and clockwise in southern hemisphere
- At center is an area of low pressure called the EYE
- The EYEWALL is rising air which spirals around the eye which generates high winds
- Near top of storm is the OUTFLOW of moist eye which causes cloud cover to extend for long distances either side of eye
How is the magnitude of a storm measured ?
Saffir-Simpson Scale
- Based on windspeed
- Categories 1-5
Explain high winds as a form of a tropical storm
- Wind speeds can reach 300km/h
- Buildings can be destroyed and trees uprooted which is carried by the wind as debris
Explain storm surges as a form of a tropical storm
- Large rise in sea level caused by high winds pushing water onto the coast and low pressure environment of a storm
- 200-300mm
Explain coastal and river flooding as a form of a tropical storm
- Heavy rain caused by warm moist air rising, cooling and condensing to create torrential rain
- Downpours cause river discharge to increase suddenly meaning rivers break their banks and flood
- In coastal areas heavy rain and storm surges cause flooding
- Agricultural areas become contaminated with sea water
Explain landslides as a form of tropical storms
- Water from heavy flooding infiltrates rock, increases pore water pressure and makes it less stable by weakening cohesion which can cause land to subside which is called slope failure
- ## 90% of landslides yearly caused by heavy rainfall
Explain the spatial distribution of tropical storms
- Form in the tropics as warm water exists there which rises and condenses which releases energy that increases wind speed
Explain the frequency of tropical storms
- Frequent: 100 a year globally
- However not all tropical storms reach land and become a major hazard
- More frequent in Northern hemisphere between June and November and in Southern between November and April
Explain the regularity of tropical storms
- Follow no spatial or temporal pattern
Explain the predictability of tropical storms
- Cloud formations associated with tropical storms can be identified with satellite imagery and storm can then be tracked to accurately predict the path of the storm
Explain a prevention strategy as a long term response to storm hazards
Can’t be prevented. Can only be studied to ensure future developments aren’t built in high risk areas
Explain 2 preparedness strategies as long term responses to storm hazards
- Educate people on preparing for a storm with emergency supply kits
- Governments plan evacuation routes
Explain 2 adaptation strategies as long term responses to storm hazards
- Use reinforced concrete to protect buildings from damage
- Build flood defenses such as levees along rivers and sea walls against coasts to protect against storm surges
How can climate change influence storm hazards ?
- Sea level rise exacerbates the impacts of storms from sea surges
- Warmer sea temperatures create more favorable conditions
Give statistic for climate change and storm hazards
The proportion of Category 4 and 5 hurricanes has increased by about 25–30% globally in the past 40 years
What type of system forms a tropical storm ?
Intense low pressure system
How wide can the diameter of a storm extend to ?
500km
What winds speeds must tropical storms exceed ?
75kmh
What are the main 2 features of a tropical storm ?
Eye and eyewall
Where do the vast majority of tropical storms form and give exception
In the tropics (5-30 degrees N and S) but can extend to regions such as China
Why can’t tropical storms form very close to the equator ?
Coreolis effect is too weak to cause storm rotation
