1.2 Hazardous Earth Flashcards
How are extreme weather events increasingly hazardous for people?
what are the characteristics of a tropical cyclone? (5)
storm surges; high winds (119-250 km/h); intense rainfall; landslides; river flooding
where are the sources for hurricanes and tropical cyclones?
sources are always near the equator.
in what direction do tropical cyclones travel in?
they travel to the north-west when formed north of the equator; they travel south-west when formed south of the equator
when do hurricanes and tropical cyclones occur?
occur during summer months - june-august (height of the hurricane season) in the northern hemisphere; during dec-feb in the southern hemisphere
sometimes extends into spring/autumn months
where do tropical cyclones/hurricanes not occur?
no/little cyclone activity further north/south 30° of the equator; dissipation at the coast
what is the structure of tropical cyclone?
surface ocean temps rise above 26.5°; storm surge in centre is caused by increased sea level due to strong surface winds (sea level is raised slightly); warm, moist air rises and is drawn inwards to the base of the eye wall; air rotates upwards in the eye wall, rotates outwards at the top; dense cirrus canopy; thick clouds, heavy rain and v strong winds in eye wall; air descends in the centre of the eye, clear sky and no wind
there are also bands of rain, tall cumulonimbus clouds and they can be up to 15km tall and 1,000km in diameter
how does a tropical cyclone form?
incoming solar radiation heats the upper ocean to at least 26.5°; the air above it is heated and rate of evaporation are high, making it also moist; rises rapidly, creating low pressure; this draws more air in and a continuous upward flow of air is created; as it cont. to rise, water vapour condenses rapidly, generating the huge amount of energy needed to power a tropical cyclone; the Coriolis effect causes it to rotate
why do tropical cyclones rotate and follow regular tracks?
air drawn in is deflected by the Coriolis effect - causes them to rotate anticlockwise in the northern hemisphere and clockwise in the southern; the effect only begins around 5°N and 5°S if the equator; the tracks followed are the direction of the prevailing winds; if it reaches as far as 30°N, prevailing winds at that latitude may start to push it north-east, giving the track a hook effect
why do some cyclones intensify?
as it continues to move across warm water, the warmer the water, the more intense the cyclone will be
why do cyclones dissipate?
they will 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 it heat source and therefore its energy; may take one or two days to dissipate; they may begin to dissipate over islands, but re-intensify is their track takes them back over water
it neither happens, it will eventually dissipates when it moves to colder water (below 26°C)
why are some countries more physically vulnerable to tropical cyclones?
coastal locations - they are most powerful when they hit land - storm surges
- Philippines is more vulnerable than the USA bc it has
the longer/est coastline - 20,000km
relief - lower-lying land is more vulnerable than higher
- USA is more vulnerable - large areas of New Orleans
are blow sea level; some Philippian islands are <3m
above sea level
geographical isolation - harder to get aid, evacuate
- Philippines is more vulnerable - many small islands
are poorly connected to larger ones; USA has well
developed infrastructure
why are some countries more socially vulnerable to tropical cyclones?
poverty - could lead to poorly built houses - increasing risks and decreasing recovery speed
- Philippines is more at risk than the USA - USA has
strict building codes; most houses in the Philippines
cannot withstand typhoons
age - older people are more at risk to health issues
- USA is more vulnerable - 49% of deaths in Katrina were 75+ year-olds; in Haiyan 39% of deaths were 60+ year olds
why are some countries more economically vulnerable to tropical cyclones?
prediction - if a country can predict them, it makes it easier for them to take measures to cope w them
- Philippines is more at risk - USA has the world’s most
advanced hurricane tracking system, Philippines has
to rely on support from Japan
coastal defences - as coastal locations are most at risk, coastal defences are needed to resist impacts
- Philippines is more at risk - USA has heavily invested
in cyclone defences, whereas Philippines has not
response procedures - the speed of recovery relies on response procedures
- Philippines is more vulnerable - USA’s FEMA is much better funded than the Philippines’ NDRRM
how can countries prepare (by monitoring and predicting) for tropical cyclones?
buoys and ships can provide pressure and winds speed data for prediction
‘hunter’ planes and dropsonde technology can be used to collect weather data from different lays of the hurricane for monitoring
super-computers can process weather and satellite data to model tropical cyclone behaviour - generates estimated track, likely points of landfall, likely patterns of intensification & dissipation, likely storm surge heights
satellite technology can monitor huge areas of the ocean for distinctive tropical cyclone cloud formations to spot and track
how can countries prepare for tropical cyclones? (advance and short term planning)
governments can invest in storm surge defences, put strict building codes in place, organise training of emergency services, put response plans in place eg emergency shelters, evacuation routes/points
public can be educated and regularly given advice on how to prepare - how to secure homes, prepare emergency packs
governments will inform public, order evacuations and order emergency services to be on standby
