5.5- Tropical Cyclone hazards Flashcards
what are tropical storms?
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
tropical storms only form over warm waters, and water this warm is only found
within the tropics between the tropic of Cancer and Capricorn
how are tropical storms formed?
- 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
What is Coriolis effect?
force caused by the Earth’s rotation- it deflects the path of the converging winds causing the winds to rotate
when do tropical storms lose strength?
when they move over land as the supply of warm-moist air is cut off
what are the different forms of storm hazard (impacts) ?
- high winds
- storm surges
- heavy rain
- flooding
- landslides
explain how high winds are a storm hazard
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
what are storm surges?
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
explain how heavy rain is a storm hazard?
As warm moist air rises it cools and condenses, causing torrential rain. For example Hurricane Katrina brought 250mm to Louisiana
explain how flooding is a storm hazard
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)
explain how landslides are storm hazards?
Water infiltrates soil and rock, making it less stable and increasing the risk of landslides
what are the different names for tropical storms in different countries?
- Caribbean sea= hurricanes
- Bay of Bengal= cyclones
- China sea= typhoons
- Northern Australia= typhoons
describe the spatial distribution of tropical storms
- 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.
storm magnitude is classified using the
Saffir-Simpson scale
what is the Saffir-Simspon scale?
- 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
what is the general frequency of tropical storms?
frequent with around 100 a year
why do many tropical storms not turn into hazards?
they don’t reach land
when are tropical storm more frequent?
- in northern hemisphere between June and November - in the southern hemisphere between November and April
The path of a tropical storm can be accurately monitored and predicted thanks to satellite imagery- explain how they can be tracked
- 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
what are a few social impacts?
- 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
what’s an environmental impact?
Beaches are eroded and coastal habitats e.g. coral reefs are damaged. Sediment deposited in aquatic ecosystems may damage fish breeding grounds
what are a couple political impacts?
- 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
what are a few economic impacts?
- Buildings cost a huge amount to rebuild
- Businesses are damaged or destroyed- stops trade
- Agricultural land id damaged affecting commercial farming
what are some short-term responses?
- 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
