Topic 1: Tropical cyclones

GCSE geography edexcel

Tropical cyclones

Large rotating storms that form over the oceans in tropical areas.

Hurricane - countries?

US, Caribbean, Atlantic

Cyclones - countries?

Uk, India, Australia

Typhoons - countries?

Japan, Philippines

Seasonal global distribution of tropical cyclones

(In book)

Characteristics of tropical cyclones

- lasting 7-14 days

- High winds over 119km/hr

- Heavy rainfall

- storm surges

- landslides

Formation

The initial development of the tropical cyclone

Source Area

A location where tropical cyclones are formed

Track

A route that a tropical cyclone takes

Immaturity

when a tropical cyclone has developed but not reached full strength

Maturity

When a tropical cyclone is fully developed and has reached full strength (max wind speed)

Decay

When a tropical cyclone loses strength and dissipates (gradually disappears)

Structure of tropical cyclones (in book)

- Tall cumulonimbus storm clouds (up to 15km)

- Dense cirrus canopy

- Winds rotate outwards at top

- Thick cloud, heavy rain and very strong winds in the eye wall

- air descends in centre of the eye

- clear sky and no wind in the eye

- air rotates upwards in the eye wall

- sea level surface is slightly raised

- warm moist air rises and is drawn inwards to the base of the eye wall

- ocean temps above 26.5°C

Why do tropical cyclones form in source areas?

- The overhead sun means incoming solar radiation is concentrated when it reaches Earth

- This heats up the upper ocean; in the summer months, temps can reach over 26.5°C

- The air above is heated, making it warm and the rate of evaporation is high, meaning the air is also moist

- The warm, moist air rises rapidly, creating low pressure and thunderstorms

- If several thunderstorms converge, the upward flow of air becomes very strong, which in turn creates extreme low pressure

- As the air rises rapidly, more air is drawn in -air naturally flows from areas of higher to lower pressure- this creates a continuous upward flow of air

- As the air continuously rises rapidly, the water vapour condenses quickly -this process generates the huge amounts of energy (the latent heat of condensation) needed to power a tropical cyclone

Why do tropical cyclones rotate and follow regular tracks?

- As air is draw in to the cyclone, it is deflected by the Coriolis effect -this causes tropical cyclones to rotate anti-clockwise in the northern hemisphere and clockwise in the southern hemisphere

- This explains why tropical cyclones form just either side on the Equator-the Coriolis effect only begins at around 5°N and 5°S of the Equator

- The tracks that tropical cyclones follow as they move away from their source area are the direction of the prevailing winds -however, the Coriolis effect is also responsible for deflecting the cyclone to the right in the Northern hemisphere and to the left in the Southern hemisphere

- If the tropical cyclone reaches as far as 30 °N, prevailing winds at that latitude may start to lush it north-east, giving the track a hook effect

Why do some tropical cyclones intensify?

As long as the tropical cyclone continues to move over warm water, it will intensify - the warmer the water, the more intense (powerful) the cyclone will be

Why do tropical cyclones dissipate?

- Tropical cyclones sometimes dissipate if they run into other ocean weather systems - if winds are blowing in different directions in the different layers of the atmosphere, the tropical cyclone will be pulled apart

- If a tropical cyclone hits land, it loses energy because it loses its heat source (the warm water) and this causes it to dissipate -this may take one or two days. Tropical cyclones begin to dissipate over islands but re-intensify if their track takes them back over water again

- If a tropical cyclone does not hit land, it will eventually dissipate when it moves into colder water (below 26.5°C)

Saffir Simspon scale?

The saffir simpson hurricane wind scale is the most common scale used to classify tropical cyclones. It is based on the wind speed generated by the tropical cyclone and estimates the likely damage to property and the environment

Hazards of Tropical Cyclones

high winds, intense rainfall, storm surges, coastal flooding, landslides

Primary impacts of tropical cyclones

- buildings and bridges destroyed

- roads, railways, ports and airports damaged

- electricity lines damaged

- sewage overflows

- rivers and coastal areas flooded

Secondary impacts of tropical cyclones

- people homeless, poverty, ill health or death due to lack of shelter

- blocked or destroyed roads prevent rescue and emergency vehicles and aid from getting through

- means of communication are prevented

- clean water supplies contaminated bringing increased risk of water bore diseases and death

- people drowned or injured. Crops, livestock and habitats destroyed leading to shortage of food and potentially famine

Vulnerability

diminished capacity of an individual or group to anticipate, cope with, resist and recover from the impact of a natural hazard

Factors which affect the vulnerability of a country to the impacts of a tropical cyclone

- Coastal locations

- Relief

- Geographic isolation

- Poverty

- Age

- Prediction

- Coastal defences

- Response procedures

How do coastal locations affect the vulnerability of a country to the impacts of a tropical cyclone?

The closer to the coast, the more vulnerable you are to storm surges flooding and high winds.

- The Philippines has over 20,000 km of coastline, the longest of any under threat from tropical cyclones

How does relief affect the vulnerability of a country to the impacts of a tropical cyclone?

Steep slopes increase risk of landslides. Low lying lands are more vulnerable.

- Large areas of the city of New Orleans, USA, are below sea level making them at high risk of tropical cyclones

How does geographic isolation affect the vulnerability of a country to the impacts of a tropical cyclone?

Smaller, isolated areas are more vulnerable as they may have poor connections to larger ones therefore they may not be informed quickly or effectively enough. It is also harder to rescue people.

- The Philippines has over 2000 inhabited islands, many of the smaller ones have poor connections to the larger ones

How does poverty affect the vulnerability of a country to the impacts of a tropical cyclone?

Developing countries are more vulnerable as badly built houses are unable to withstand typhoons

- The USA has strict building codes in hurricane risk areas and are able to afford materials to build buildings able to withstand typhoons however many houses in the Philippines are built informally and cannot withstand typhoons

How does age affect the vulnerability of a country to the impacts of a tropical cyclone?

As age increases, vulnerability also increases

- In hurricane Katrina, USA, 49% of those killed were over 75 years of age

- In typhoon Haiyan, Philippines, 39% of those killed were over 60

How do predictions affect the vulnerability of a country to the impacts of a tropical cyclone?

Developed countries have abilities to predict cyclones due to advanced technology allowing them to prepare/ evacuate making them less vulnerable

- The USA has the world's most advanced hurricane prediction, whereas the Philippines relies on support from Japan to track typhoons

How do coastal defences affect the vulnerability of a country to the impacts of a tropical cyclone?

Developing countries are unable to invest in protection like sea walls/ levees increasing the risk

- The GDP per capita of the USA is $53,000 compared to $2800 for the Philippines; the USA has invested heavily in sea walls and river/ canal levees but the Philippines has not

How do response procedures affect the vulnerability of a country to the impacts of a tropical cyclone?

Developed countries have better response procedures allowing them to recover from tropical cyclones more quickly and effectively making them less vulnerable

- The USA has a disaster management agency called FEMA and the Philippines has one called MDRRMC however the Us agency is by far the best funded

Measuring atmospheric pressure:

Buoys are anchored in tropical ocean areas and provide pressure and wind speed data. Ships also record this data and send records ashore

Monitoring tropical cyclone development:

Some countries.

such as the USA, have highly

sophisticated monitoring technology. The National Hurricane Centre uses 'hunter' planes and dropsonde technology to collect weather data from the difterent layers in a hurricane (e.g wind speed, pressure)

Tracking tropical cyclones:

Satellites technology allows for huge areas of ocean to be monitored for distinctive tropical cyclone cloud formations. Once the eye has formed, these are easy to spot.

Modelling tropical cyclones:

Super-computers can process weather and satellite data to model tropical cyclone behaviour; this generates estimates of likely tracks of tropical cyclones, likely points of landfall and likely patterns of intensification and dissipation, plus likely storm surge heights.

Advance planning:

Governments of countries at risk of tropical cyclones will invest in storm surge defences, may put strict building codes in place, will organise training of emergency services and put response plans in place, for example emergency shelters and evacuation routes and points. In the USA, the Federal Emergency Management Agency (FEMA) is responsible for disaster planning and response.

Education and awareness:

In countries at risk of tropical cyclones, the public are regularly given advice on being prepared for a tropical cyclone. This includes how to secure your home from damage, preparing emergency packs and what foute to take in an evacuation and what to bring.

Communicating information:

When a tropical cyclone is forecast to make landfall in a country, the government will inform the public, order evacuations of people in areas of risk and order emergency services to be on standby.

Implementing actions:

Governments activate any defences it has in the area, such as flood barriers or storm surge barriers, supports evacuations, and the public implement their personal action plans

Search and rescue:

Teams search for people trapped in buildings or on roofs in flooded areas vehicles, boats, helicopters may be deployed.

Emergency supplies:

Food, clean water and medical care provided where necessary, and shelters for those displaced by the tropical cyclone

Repair and reconstruction:

Restoration of electricity supplies and drinking water, and the clearing roads to facilitate travel. Longer term rebuilding of properties and infrastructure.

Hurricane Katrina:

- place?

- Year?

- Category at landfall?

- Height of storm surge (metres)?

- Number evacuated?

- Number of deaths inc missing?

- Homeless

- Economic cost

Place - USA

Year - 2005

Category at landfall - 3

Height of storm surge - 6

Number evacuated - 1.3 million

Number of deaths - 1800

Homeless - 400,000

Economic cost - $100 billion

Typhoon Haiyan:

- place?

- Year?

- Category at landfall?

- Height of storm surge (metres)?

- Number evacuated?

- Number of deaths inc missing?

- Homeless

- Economic cost

Place - Philippines

Year - 2013

Category at landfall - 5

storm surge height - 5

Number evacuated - 0.8 million

Number of deaths - 7400

Homeless - 4 million

Economic cost - 3 billion

Preparation strengths of Hurricane Katrina

- Good forecasting and tracking services, detailed and accurate

- encourage inhabitants to evacuate, approx 80% of city's population were evacuated before hurricane hit

- Football stadium (super dome) was designated as a shelter for inhabitants

Preparation limitations of Hurricane Katrina

- not everyone could evacuate as some did not have access to a car

- Many levees and barriers overwhelmed as they had not been properly maintained or upgraded (80% of the city was flooded)

- poorest suffered the most

Response strengths of hurricane Katrina

- improvement in recruitment and staff training at FEMA

- all levees rebuilt at a cost of $14 billion

Response limitations of Hurricane Katrina

- local and national governments not fast or effective enough

- people evacuated to the super dome had limited food and water

- The FEMA (Federal Emergency Management Agency) were unprepared for the scale of destruction and there were many more people needing help than FEMA could cope with

Preparation strengths of Typhoon Haiyan

- Philippines was assisted in tracking the typhoon with data from Japan

- Government used the public storm warning signal (PSWS) system to warn people across the country of the risk they faced

- People in areas at risk of flood evacuated to safer areas

- The military were ordered to send planes and helicopters

Preparation limitations of Typhoon Haiyan

- In some areas, government emergency shelters were not on high enough ground to escape the massive 5m surge

- Warning were initially only a level 1 meaning the data was not accurate

- limited time for people to respond

- there are many regional languages in the Philippines meaning warnings did not get to everyone

Response strengths of typhoon Haiyan

- over 1200 evacuation shelters were set up to help the homeless

Response limitations of Typhoon Haiyan

- The relief effort was slowed by blocked roads and damage to local airports

- Some areas remained isolated for days with no sources of clean water available due to burst pipes and contamination from sea water, many people without safe water for a long time

- the shelter response was underfunded and took longer to implement than expected.