5.5- Tropical Cyclone hazards

Question 1

what are tropical storms?

Answer 1

huge spinning storms with strong winds (over 250km/hr) and torrential rain- they are circular in shape, hundreds of kilometres wide and usually last 7-14 days

Question 2

tropical storms only form over warm waters, and water this warm is only found

Answer 2

within the tropics between the tropic of Cancer and Capricorn

Question 3

how are tropical storms formed?

Answer 3

• as warm moist air rises over the tropical oceans it cools, condenses and forms storm clouds
• the sea temp needs to be at least 27 degrees celcius to at least 50m deep to encourage huge amounts of evaporation
• this results in an area of low pressure at the surface
• as warm air rises, cooler air is drawn in towards the centre of low pressure; this area of air convergence forces the rising warm air upwards
• The ITCZ where two limbs of the Hadley cell converge to form low pressure on the ground provides perfect conditions for the formation of tropical storms

Question 4

What is Coriolis effect?

Answer 4

force caused by the Earth’s rotation- it deflects the path of the converging winds causing the winds to rotate

Question 5

when do tropical storms lose strength?

Answer 5

when they move over land as the supply of warm-moist air is cut off

Question 6

what are the different forms of storm hazard (impacts) ?

Answer 6

• high winds
• storm surges
• heavy rain
• flooding
• landslides

Question 7

explain how high winds are a storm hazard

Answer 7

Wind speeds on the ground can exceed 300km/hr. Wind can destroy buildings, uproot trees. Wind carries debris like cars and branches makes the wind extremely damaging and dangerous

Question 8

what are storm surges?

Answer 8

a large rise in sea level caused by the low pressure of the storm- drawing the sea surface upwards. This is enhanced by strong winds blowing this water towards the coast resulting in coastal flooding. The sea level is typically 3-5m above normal tide level

Question 9

explain how heavy rain is a storm hazard?

Answer 9

As warm moist air rises it cools and condenses, causing torrential rain. For example Hurricane Katrina brought 250mm to Louisiana

Question 10

explain how flooding is a storm hazard

Answer 10

Heavy and prolonged rainfall can cause river discharge to increase. This can result in rivers bursting their banks and flooding the surrounding area (see also the links with storm surges and flooding at the coast)

Question 11

explain how landslides are storm hazards?

Answer 11

Water infiltrates soil and rock, making it less stable and increasing the risk of landslides

Question 12

what are the different names for tropical storms in different countries?

Answer 12

• Caribbean sea= hurricanes
• Bay of Bengal= cyclones
• China sea= typhoons
• Northern Australia= typhoons

Question 13

describe the spatial distribution of tropical storms

Answer 13

• tropical storms don’t form between 0-5° north and south of the equator due to the Coriolis effect being weak
• due to the influence of the Coriolis effect tropical storms move away from the equator and rotate anticlockwise in the northern hemisphere and clockwise in the southern hemisphere.

Question 14

storm magnitude is classified using the

Answer 14

Saffir-Simpson scale

Question 15

what is the Saffir-Simspon scale?

Answer 15

• scale is based on wind speed and estimates the resulting damage:
• category 5 is the strongest with winds over 250 km/hr resulting in catastrophic damage. Category 1 is the weakest with winds 120-150 km/hr resulting in limited damage

Question 16

what is the general frequency of tropical storms?

Answer 16

frequent with around 100 a year

Question 17

why do many tropical storms not turn into hazards?

Answer 17

they don’t reach land

Question 18

when are tropical storm more frequent?

Answer 18

• in northern hemisphere between June and November - in the southern hemisphere between November and April

Question 19

The path of a tropical storm can be accurately monitored and predicted thanks to satellite imagery- explain how they can be tracked

Answer 19

• storms can be tracked using satellite imagery
• computer models based on historical data help scientists understand where the storm is likely to make landfall
• these areas can then receive warnings in good time to make arrangements, secure buildings and services and evacuate if necessary

Question 20

what are a few social impacts?

Answer 20

• People drown on flood water or killed by wind-blown debris.
• Houses destroyed so people are left homeless.
• Electricity cables damaged- supply cut-off
• Flooding causes sewage to overflow and contaminate water. This can result in the spread of diseases

Question 21

what’s an environmental impact?

Answer 21

Beaches are eroded and coastal habitats e.g. coral reefs are damaged. Sediment deposited in aquatic ecosystems may damage fish breeding grounds

Question 22

what are a couple political impacts?

Answer 22

• Authorities may be blamed for shortages of food, water and energy. This could result in looting, conflict and political unrest
• Expensive repairs to buildings and services can hinder a countries development

Question 23

what are a few economic impacts?

Answer 23

• Buildings cost a huge amount to rebuild
• Businesses are damaged or destroyed- stops trade
• Agricultural land id damaged affecting commercial farming

Question 24

what are some short-term responses?

Answer 24

• people secure their properties and board up their windows to reduce the damaging effects of the tropical storm e.g. strong winds and torrential rain
• preparing emergency supplies to enable them to be more self-sufficient in the aftermath
• planning evacuation routes if the risk is high enough
• mass evacuation programmes have been extremely successful in saving lives
• in some locations prone to tropical storms, people have had to adapt to the problem making use of emergency shelters e.g. Bangladesh and the Philippines

Question 25

what are some further short-term responses?

Answer 25

• depending on the scale, following the disaster communities rally together to search for people and possessions, repair damage and clear up the local environment
• governments may declare a state of emergency- this triggers/mobilises the armed forces and emergency services
• help from the international community may be sought by the government, this could come in a variety of forms depending on need: Experts e.g. doctors, engineers, search and rescue; transport or relief supplies e.g. food, water and shelter
• aid can also arrive from trading blocs such as the EU or international bodies like the World Bank or he UN. Charities and NGOs provide donations and support

Question 26

what is involved in long-term responses?

Answer 26

• preparedness
• mitigation
• prevention
• adaption

Question 27

what is involved in preparedness?

Answer 27

• scientists study and monitor tropical storms using satellites and radar to identify the areas most at risk
• the USA and Caribbean issue a ‘Hurricane watch’- 36 hrs warning, this is then upgraded to a ‘Hurricane warning’ is the risk is still present with 24hrs notice
• governments plan evacuation routes and educate people about how to prepare. Emergency services and authorities train and prepare for disasters

Question 28

what is involved in mitigation?

Answer 28

1- structural intervention- Soft engineering (e.g. planting mangrove trees) and Hard engineering schemes (e.g. sea walls) can be implemented to offer protection from storm surges. In the South Carolina, USA the Safe Homes Programme provides grants to homeowners to make their homes more resilient to wind damage, this includes strengthening roofs and installing stronger windows
2- Insurance cover- is widely used particularly in MEDCs. People take out insurance cover against wind damage and have to follow strict building codes and regulations. Social issues with this approach as only the wealthy can afford the high premiums. The poorest people in New Orleans were the hardest hit during Hurricane Katrina, 2005

Question 29

what is involved in prevention?

Answer 29

• tropical storms cannot be prevented. Understanding of vulnerable locations enables future developments to be appropriate to the setting. Highly vulnerable coastal areas can be avoided in new developments
• ‘Cloud seeding’ (dropping crystals into clouds to encourage rain) is an approach that has been used (unsuccessfully) in an attempt to dissipate clouds

Question 30

what is involved in adaption?

Answer 30

• People learn to live with the threat of tropical storms and do what they can to minimise the risks
• Adaptation includes elements of preparation and mitigation
• Land-use zoning aims to reduce the vulnerability of people and property in high risk coastal locations
• Levees can be built along rivers
• In Australia wind resistant structures are built and regularly inspected and maintained