1c - Tropical Storms Flashcards
What are Tropical Cyclones?
Tropical cyclones are intense low pressure weather systems with heavy rain and strong winds that spiral around the centre
Include: hurricanes, cyclones, typhoons - all same, just different location
What is needed for tropical cyclones to form?
- sea temp of 27 degrees or higher
- low wind shear in the upper atmosphere
- source location in the tropics (8-20 degrees N/S of equator)
- westerly trade winds
How do tropical cyclones form?
- Warm surface water evaporates, rises and condenses, releasing lots of energy powering the storm
- The rising air drawn up quickly creating an area of low pressure, increasing surface winds
- Due to Coriolis force (winds moving in specific direction due to Earth’s axis) the storm spins
- When rising air reaches top of cyclone, air flows away from the centre and descends forming the eye wall
- As the storm moves over the ocean, energy from warm water strengthens storm, so increased windspeed
- Storm loses its strength when moving over land/cool water due to energy supply being cut off causing it to dissipate
What is the structure of tropical cyclones?
- alternating bands of rising and sinking air around a central eye
- rapidly rising air forms cumulonimbus clouds and rainfall
- eye has low pressure, light winds, no cloud or rain, high temp
- eye surrounded by eyewall, where there’s spiralling rising air, very strong winds, storm clouds, torrential rain, low temps
- spins anticlockwise in northern hemisphere and clockwise in southern
How are tropical storms measured?
- using the Saffir-Simpson scale
- based only on the measured, sustained wind speed
How do tropical cyclones intensify and dissipate?
Tropical cyclones intensify when water temperatures are warm, there is a low wind shear and high humidity
Tropical cyclones dissipate when they reach land so lose energy, move into colder waters and run into other weather systems where winds are blowing in different direction
What physical hazards do tropical cyclones cause?
High winds
Intense rainfall
Storm surges - a large rise in sea level caused by low pressure, high winds
Coastal flooding - caused by storm surges and strong winds driving large waves onto shore
Landslides - heavy rain makes hills unstable causing landslides
What are the impacts of tropical cyclones on people?
- drowning in currents created by floodwater, storm surges
- wind speeds can destroy buildings, homelessness
- high winds and floodwater can carry debris which kills/injures people
- electricity supplies cut off because cables damaged by flood water
- flooding causes sewage overthrow, contaminating water supplies making it easier for disease to spread
- shortage of food as crops damaged and livestock killed
- damaged roads makes it difficult for aid & emergency vehicles to get through
What impacts do tropical cyclones have on the environment?
- trees uprooted by high winds which can damage/destroy wooded habitats
- storm surges can erode beaches and damage coastal habitats
- flooding can damage industrial buildings on the coast causing harmful chemicals to leak into the environment
- landslides deposit sediment in rivers and lakes which can kill fish/wildlife
Why are some countries more physically vulnerable than others to the impacts of tropical cyclones?
- low lying coastlines are vulnerable to storm surge flooding as well as large waves caused by high winds
- areas in the path of the tropical cyclones are hit more frequently
- steep hillsides may increase the risk of landslides
Why are some countries more socially vulnerable than others to the impacts of tropical cyclones?
Poorer countries are often more socially vulnerable as:
- health care is poor so they struggle to treat all casualties
- there is less money for flood defences/ training emergency teams
- its hard to rescue people due to poor infrastructure
- often higher pop. density in low quality buildings which are easily damaged
Why are some countries more economically vulnerable than others to the impacts of tropical cyclones?
Poorer countries are more economically vulnerable:
- people may not have insurance to cover cost of repairing damages
- many people depend on agriculture which is often badly affected leading to a loss of livelihoods
Economic impact is often greater in richer countries as the buildings/infrastructure is worth a lot more
How can countries predict tropical cyclones?
Weather forecasting - to predict its track and estimate likely storm surge heights and rainfall levels
Satellite technology - can be used to spot and track cloud formation
How can countries prepare for tropical cyclones?
ST: Warning and evacuation strategies - alerts people, giving them time to leave their home & govs can plan evacuation routes
Setting up shelters, emergency hospitals
LT: Flood defences - sea walls & levees could protect against storm surges
Education - residents know about dangers and how to respond
What were the environmental impacts on Hurricane Harvey, Houston?
- 30,000 gallons of crude oil spilled from damaged oil refineries into Gulf of Mexico
- alligators displaced and found all over Houston
- spike in people with West Nile virus, carried by mosquitoes living by stagnant water
What were the environmental impacts on Typhonn Haiyan, Philippines?
70,000ha of farmland ruined across Philippines
30,000ha of tropical mangroves lost - no protection against future storms
7m high waves - 5m storm surges hit 6 islands
Communication between 6 islands cut so ppl isolated for weeks
What were the social impacts on Hurricane Harvey, Houston?
107 deaths caused mainly by flooding
1000 damaged homes + 17000 with major damage
30,000 people displaced
What were the social impacts on Typhoon Haiyan, Philippines
7000 killed
6 million displaced and 1.9 million left homeless
Tacloban gov devastated with 70/2500 able to work
What were the economic impacts on Hurricane Harvey, Houston?
$125 billion of damage
Oil refineries closed - fuel shortage, 12% drop in US oil production
Texas cotton harvest damaged
US insurance companies with bill of $10bn
What were the economic impacts on Typhoon Haiyan, Philippines?
$5.8 billion damage
6 million workers lost income
Rice, corn & sugar production destroyed
Tacloban City Airport flooded so planes couldn’t land
Philippine fishing communities lost 30,000 boats
What was the response to Hurricane Harvey, Houston?
- charity response eg American RedCross
- commercial planes used to evacuate and bring supplies
- local companies provided meals for volunteers and victims
- Mexico sent volunteers, Israel sent $1m, Singapore shared Chinook helicopters and Venezuela provided $5m
- federal gov provided $15bn for flood insurance, low interest rebuilding loans and hotel room costs
What was the response to Typhoon Haiyan, Philippines?
- 2 days warning
- 750,000 evacuated
- nearly £500m raised by global UN appeal
- UK (DHL) provided portable toilets, hygiene supplies and psychological first aid
- emergency aid from charity - repairing fishing boats and distributing rice seeds
- Taiwan mobilised 31,000 workers to clear debris
