Hazards - Tropical Storms Flashcards
(22 cards)
What is a tropical storm?
An intense low pressure weather system with winds above 74mph, that can last for days to weeks within the topical regions of our planet
Where do they form?
Between 5 and 30° N or S of the equator
Make landfall on eastern coasts of continents due to the earth’s rotation
What are the key conditions needed for a tropical storm to form?
Sea temps of 27°c or higher to a depth of at least 70m - provides enough heat and moisture for water to evaporate and create a storm
Location at least 5° N or S of the equator - provides strong enough coriolis effect
Low pressure
Low - level convergence of air in atmosphere
What direction do they travel in the northern and southern hemisphere?
Northern - anti-clockwise
Southern - clockwise
How are they formed?
- Atmospheric disturbance over warm seas between 5 and 30° N and S
- Air rises and cools, forming clouds and process of condensation releases latent heat, creating more warming and rising.
- This deepens low pressure area and winds converge as air moves from high to low pressure.
- Due to winds and coriolis effect the storm starts to spin. Moves over oceans and gathers moist air that rises, releasing latent heat.
- Storm grows, once wind speed reaches 74mph it is considered a tropical storm.
- Air descends around storm and fuels it more creating a positive feedback loop. When tropical storms reach land they lose energy and friction with land surface causes storm to dissipate.
What are the 5 forms of hazard associated with tropical storms?
Heavy rain, high winds, landslide, river flooding, storm surges
What are the social impacts of hazards?
People killed/ injured
People left homeless and houses destroyed
Flooding causes sewage to overflow, contaminating water supplies.
What are the economic impacts of hazards?
Buildings / infrastructure cost huge amount of money to repair
Businesses damaged so can’t trade
What are the environmental impacts of hazards?
Beaches eroded and coastal habitats destroyed eg) coral reefs
Land polluted by salt water and oil / chemical spills from factories
What are the political impacts of hazards?
People blame authorities for food / water shortages leading to conflict / political unrest
How many storms do tropical oceans generate per year?
Around 80-100
Which ocean generates the highest number of storms?
Pacific Ocean
When do storms occur in the northern and southern hemisphere?
Majority in summer to autumn as this is when sea temps are at their highest
Northern Hemisphere- July-October
Southern Hemisphere - December-March
What is happening to tropical storm intensity?
Becoming more intense
What has happened to the energy released by the average storm?
It has been calculated that the energy released by the average storm has increased by 70% in the past 30 years.
What measures tropical storms?
Saffir Simpson scale
What is the saffir Simpson scale and what are the categories/ wind speeds ?
The scale measures storms from category 1-5
1 and 2 are classified as non-major
3-5 are classified as major
Minimum windspeed for category 1 is 74mph
Minimum windspeed for category 5 is 157mph
What are limitations of the saffir Simpson scale?
Does not assess impact
Does not assess all associated hazards, eg) rainfall
Area affected is not taken into account
Tropical storm - preparation
Satellite and radar technology used to track the development and approach of a tropical storm can predict path storm should take
HICs such as the USA, have an effective hurricane monitoring and prediction system because they have the finances available to invest in these
National Hurricane Centre in Florida tracks all hurricane activity over eastern pacific and Atlantic
a hurricane watch is issued when hurricane-strength winds are detected to alert people and give them time to prepare. The National Weather Service publicises this information.
In Florida, evacuation routes and cyclone shelters are clearly signposted.
Individual families are encouraged to make a plan and have provisions ready in case they need to act quickly. People are also urged to take out insurance.
Tropical storm - mitigation
Structural responses include soft and hard engineering schemes.
Along some coastlines (e.g. north-east India) trees, such as mangroves, are planted to protect coastal communities whilst in other areas (e.g.Texas) the construction of sea walls may be more appropriate. Grants may also be given to households to make their property more able to withstand storm hazards. This includes strengthening roofs and reinforcing gable ends.
Disaster aid includes both immediate relief and longer-term aid. The priority in the immediate aftermath of any disaster is to save lives and prevent any further loss of life. Governments may declare a state of emergency and mobilise the armed forces in addition to emergency services. Aid can come from trading blocs such the EU or from international bodies such as the World Bank or the United Nations.
Insurance cover used particularly in HICs.
Eg) in the USA, people in hurricane-prone areas are encouraged to take out insurance against wind damage
and to follow certain building codes and regulations.
Insurance is only an option for the wealthiest, however, who can afford the high premiums.
This can result in richer people being more likely to evacuate, in the knowledge that their property and possessions are covered, whilst the poorest may stay to protect their home and its contents. This happened in New Orleans in 2005 when Hurricane Katrina struck.
Tropical storm - prevention
Like other natural hazards, tropical storms cannot really be prevented
but there has been research into the use of cloud seeding in order to cause more precipitation which could
potentially force more water to be released over the sea, weakening the storm system as it approached land.
However, concerns about knock-on effects has led to the search being halted.
Tropical storms - adaption
land-use zoning to reduce the vulnerability of people and property at the coast.
Usually, low-value land use is permitted along the coastal strip e.g. recreation, whilst high-value land use
occupies higher ground.
Coastal properties can also be adapted to reduce vulnerability to flooding. Eg) In Florida, some houses are raised above the ground on stilts or have non-residential functions on the ground floor, such as a garage.
In poorer countries, people are also building properties more able to withstand effects. Eg) Bangladesh NGOs helped communities build stronger houses in concrete stilts designed to withstand tidal surges. Buildings constructed of brick rather than bamboo with reinforced roofs and solid doors and windows.
