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Tropical Cyclones and Droughts - Coggle Diagram
Tropical Cyclones and Droughts
2.5
a. + b.
a tropical cyclone (hurricane/typhoon/cyclone) is a rotating storm characterised by an intense low-pressure centre =, strong winds and spiralling thunderstorms that produce heavy rainfall
collectively tropical storms
originate near the equator (no on equator -> coriolis effect does not have as much impact at equator)
do not reach higher latitudes (belts of high pressure dissipates them, also lost heat + energy)
coastal
coriolis effect causes a bending pathway (away from equator)
global atmospheric circulation has an impact on the formation of tropical cyclones. as air moves around the planet, it begins to rotate because of the need to disperse the high levels of heat at the equator across the planet's surface. the movement, as result of the coriolis effect, combined with the evaporation caused by higher temperatures, leads to the formation of tropical storms
tropical storms form near the equator, between the tropics. tropical storms do not reach higher latitudes, so do not go very far N/S - curve away from equator, but do not reach high latitudes. concentrated in equatorial areas. tropical storms form particularly near America, especially central America and near Mexico and also in the Indian Ocean, in Indonesia and the Caribbean and also on the east coast of Africa and Madagascar. predominantly in coastal areas.
formation
equatorial areas - but some distance so coriolis effect impacts, temperatures greater than (/equal to) 27 degrees C, ocean depth of >= 60m
initial low pressure - causes evaporation, warm, rising air = storm
intensified low pressure - condensation releases latent heat which injects more energy into the storm, intensifying low pressure
revolving storm - coriolis effect causes rotation. rotating storm pulls air vertically, creating the 'eye' of the storm - a pocket of high pressure
storm surge - huge tidal wave accompanies hurricane. strong winds push the storm in a direction, intense low pressure draws up the sea level, causing a storm surge
tropical storms do not remain where they are formed. cyclones follow the direction of local prevailing winds and ocean currents. the track of the tropical cyclone affects how strong it becomes. the further it travels over the ocean, the more heat and moisture it collect, so increasing its strength. when the cyclone reaches dry land, it is cut off from its energy source. it can no longer extract heat from the ocean, loses strength and slows.
the formation of tropical cyclones can be forecast and the track of the cyclone can be predicted, to allow preparations to be made as potential landfall locations
because a tropical cyclone requires specific conditions for its formation, they are more likely to occur in some periods of the year than others, e.g. more likely to form between june and november in the northern tropics and between november and april in the southern tropics - periods where tropical cyclone formation is more likely are referred to as seasons.
it is impossible to predict how many tropical storms will be formed in a season and how many will become cyclones. in warmer years more cyclones are more likely, but numbers will vary. since 1968, an average of 12 named hurricanes have formed each season
2.6
b. + c.
Typhoon Haiyan - Philippines
affected Philippines (SE Asia) in November 2013
one of strongest tropical cyclones ever recorded, winds of 313 km/h
281.9mm of rainfall recorded in some areas, most falling in less than 12 hours
waves up to 7m high
Philippines is a fairly poor part of the world, with minimal investment in prediction, planning + protection schemes
impacts
social
7,000+ killed
1.9mil left homeless, 6mil displaced
outbreaks of disease due to lack of sanitation, food, water, shelter + medication
huge no.'s of refugees - less affected areas reported populations more than doubled due to this
Tacloban city govt. devastated - 70/2500 people at work in the immediate days after the disaster - many killed, injured, lost family or were too traumatised to work
widespread looting took place in Tacloban in the days following the typhoon
environmental
widespread floods - damaged or destroyed homes + businesses in coastal areas
est. 71,000 hectares of farmland affected
1000s of trees uprooted - massive release of CO2 + loss of habitat with resulting effects on wildlife
flooding knocked over Power Barge 103 - resulting oil spill affecting mangrove ecosystems
major roads blocked by trees
economic
overall est. $5.8bn (£3.83bn)
6 mil workers lost their sources of income
major rice, corn + sugar-producing areas in Philippines destroyed - affecting international trade + farmer's incomes
Tacloban's city airport damaged - loss of business + tourism
30,000 boats and associated equipment destroyed
responses
PAGASA - Philippines' meteorological agency - broadcast warnings 2 days before Typhoon Haiyan hit - evacuation of approx. 750,000 residents, reducing loss of life
Philippines formally declared 'A State of National Calamity' + asked for international help 1 day after Typhoon Haiyan hit the country
UK govt. provided shelter, clean water, medicine and other supplies for up to 800,000 victims
several charities provided emergency aid such as water, food and shelter. in the longer term, they are helping people get their livelihoods back, e.g. by repairing fishing boats or distributing rice seeds
UN launched and international aid appeal in December 2013 for £480mil to finance the humanitarian relief effort for 2014
in 2014, the Philippines commissioned billboards in some the world's prime advertising sites (e.g. Times Square and Piccadilly Circus) to thank people for their help
Hurricane Sandy - USA
occurred October 2012
hit east coast of USA
USA MEDC - had resources to prepare for/respond to the tropical cyclone quickly + effectively
impacts
social
at least 286 people killed directly/indirectly (72 direct in USA)
power failure at New York University Langone Medical Centre - evacuation of all 215 patients to other hospitals
people highly stresses + anxious, in longer term, people could have been affected psychologically by loss of family + friends
8.5mil+ homes + businesses left w/o power
Washington DC/other cities - many supermarkets ran out of essentials e.g. bottled water + batteries as people prepared for the worst
NYC marathon cancelled - loss of income for many businesses
environmental
346,000 houses damaged/destroyed in New Jersey, 305,000 damaged/destroyed in New York
fallen trees + flooded vegetation affected habitats
in some areas (New Jersey/New York), untreated sewage was washed into public drinking water, threatening human health
roads, train lines + other transport infrastructure became unusable due to flooding - disruptions to travel + work
approx. 10m of beach lost in some areas of New Jersey (narrower) - exposing coast to further erosion + impacting wildlife
economic
$71bn in damages (NYC $18bn+)
buildings, cars, possessions + business stock lost
18,000+ flights cancelled - disruption in business, tourism + trade
crops lost - loss of earnings for farmers
responses
USA invested more into tropical cyclone prediction, planning and protection
National Hurricane Centre in Miami predicted + monitored path of Hurricane Sandy, and was able to issue warnings to the local authorities + general public - helped reduce impact
steps taken to minimise damage:
President (Obama) + authorities appealed to people to stay calm + out of harm's way
police evacuated 100,000s of people from low-lying coastal areas most vulnerable to Hurricane Sandy
schools + public transport services closed down - many flights cancelled
people temporarily relocated to evacuation centres e.g. schools + community centres
a.
why tropical cyclones are natural weather hazards
storm surges
creates a large area of low pressure, which allows the sea level to rise
when this is combined with the high winds produced by the storm, a large mass of water can be forced towards the land by the strength of the wind
when the surge hits land, it does so with severe force
can erode beaches and coastal habitats, damage coastal defences and flow inland, contaminating farmland and freshwater areas such as lakes
coastal flooding
combination of intense rain and storm surges puts coastal areas at severe risk of flooding
not only puts people and property at risk, but can also affect the farming and tourism industries
environmental impact of flooding by salt water will also be very damaging
intense rainfall
as tropical cyclones move over the ocean they take up a large amount of water and this results in a large release of rain
weather forecasts can estimate how much rain may fall based on how fast the storm has been travelling over the water
intense rain can lead to flooding, damage to property and injury as fast-flooding water can knock people over, even if it is not particularly deep
landslides
intense rainfall affects areas of high relief as well as coastal lowlands. high levels of rain can saturate the soil very quickly, making the soil very heavy and, in areas with steep slopes, can mean the soil will no longer be able to hold its position and will start to slide down the slope
deforestation can make slopes unstable, as can the geology (e.g. where the underlying rock is impermeable) so the wet soil and rock above can easily slide over it and downhill
can cause massive devastation to any settlements at the base of the slope, and cause river flooding if the landslide blocks river channels
high winds
produce winds of over 119km/h
can cause severe damage to buildings, trees can be uprooted and some smaller constructions (sheds, beach huts) can be moved
these become dangerous as they can impact on people and buildings, causing damage, injury and loss of life
2.7
b.
causes of drought
hydrological causes
refers to a lack of water in the hydrological system
it will be seen as abnormally low flow in rivers and abnormally low levels in lakes, reservoirs and groundwater
e.g. California
(may have same cause as meteorological, but effects different/less obvious)
human causes
dams
dams are built on rivers to act as flood defences, to create stores of water and to provide electricity through hydroelectric power
but it does this by restricting the flow of water in the river
this can lead to a drop in water levels further downstream, leaving and area in drought as it no longer receives the same amount of water as before the construction of the dam
deforestation
locally:
trees supply moisture into the atmosphere through transpiration, which leads to cloud formation + precipitation
losing trees eradicates this link between vegetation + atmosphere
globally:
trees take in CO2
with fewer trees, there will be more CO2 in the atmosphere enhancing the greenhouse effect
this will create warmer temperatures and increase drought risk
agriculture
intensive or large scale agriculture is highly dependent on water
when several agricultural systems rely on the same water source, overexploitation occurs leading to intense water shortages
the aral sea was once the fourth largest lake in the world, however, during the soviet occupation of central Asia, there was intense pressure on agriculture. vast areas depended on the aral sea for water, and it was unsustainably depleted
meteorological causes
level of dryness in an area due to an area receiving less precipitation than normal (an area can be classified as being in drought even if it receives more rainfall than other areas -> based on what is normal for the area)
most significant cause of drought
due to a change in the usual weather and climate patterns in an area
large-scale changed in weather + climate
closely linked to climate change e.g. increasing global temps + climate change -> dramatic shifts in temp and rainfall
mid-latitudes (where droughts most likely to happen) -> high atmospheric pressure
e.g. Ethiopia
c.
how global circulation makes some locations more vulnerable to drought
when the precipitation occurs
if the rainy season is during winter, there are lower temps and less intense sunlight, so water is absorbed by soil with relative ease - water is stored underground and will be available during drier months
if precipitation occurs during summer months, water is not as easily absorbed by soil
rain falls on soil that is likely to be baked hard by intense sunlight and therefore is more difficult for to soak in
there will also be higher rates of evaporation because of the higher temperatures - so more will evaporate before it soaks in
drought is therefore a more likely occurrence
drought also varies in severity
UK is less susceptible to drought, but can have drought conditions e.g. hosepipe bans and reservoirs drying up
impacts are in stark contrasts to those caused by drought conditions in areas such as the Sahel, where drought causes life-threatening conditions for many people
how an area receives its precipitation - throughout the year/in a rainy season
countries that receive rain throughout the year (e.g. UK) do not rely on a particular rainy season
places that receive the majority of their rainfall during particular months (e.g. the Sahel in central Africa and the 'monsoon' season in India) are more vulnerable to drought
drought results if changes in global circulation patterns mean the rains are delayed or weaker than normal, they do not produce as much rainfall or may even fail completely
if a place relies on rain coming at a specific time and this does not happen, it can have significant effects on farming etc. unlike a place that receives rain through the year which have more consistent rainfall
a.
arid environments do not suffer from droughts as aridity (low precipitation) is already the normal climate for the area
this is because they are located in regions which normally have high pressure e.g. where the Hadley and Ferrel cells meet and dry air, so clouds unlikely to form and they will have low levels of precipitation throughout the year
2.8
b. + c.
drought in California
causes
a period of lower than lower rainfall and snowfall across the western side of the USA caused a distinct drop in water supplied for California
made worse by the fact that most of California's water comes from the Colorado River, which also provides water for six other states
states had been allowed to extract more water from the river than it receives, leading to a reduction in availability
combined with a very high level of wastage and over-use, water was becoming a very scarce commodity
impacts
subsidence - as surface water flows decrease, water is increasingly extracted from groundwater and aquifers to maintain supplies, changing the structure of the land, can cause it to settle to a lower level, causing infrastructure and building damage
seawater intrusion - natural groundwater flow (towards sea) is reversed because a lack of flow pressure, so groundwater supplies become contaminated with seawater, making them unusable or expensive to use for domestic/agricultural purposes
when water is diverted for domestic/agricultural use, wetlands and rivers receive less water - these environments suffer from lack of water faster as amount of water is being reduced both naturally and artificially. adverse effect on birds and fish
wildfires - warm + windy weather across the state dried out vegetation, making it easy for fire to start and spreads quickly. fires cause environmental damage and put lives and property at risk, but ash and debris from the fires also gets into water supplies, contaminating them
farming - farmers have had to adapt to the drier climate. 2015, farms lost est. $18.8bn and 10,000 jobs due to the drought. some increases in food prices.
power - reduced output of hydro-electric power stations + thermal stations require large amounts of cooling water, so reduced power output
2012-present
California one of the wealthiest states in the USA, a developed + rich country
January 2014, a state of emergency was declared by the state governor, allowing new laws and regulations to be put in place to deal with the drought
responses
limiting flows during winter months to try to build reserves for later in the year, when demand is higher
warning some areas they will be given limits on how much water they will receive because river levels are too low
reducing water supplies down to the minimum allowed for public health and safety
installing salinity control points in crucial areas, to prevent seawater intrusion
running education and information programmes to encourage people to use as little water as possible at home
increased monitoring of some rivers to check on levels of endangered species and the effects of the drought on them
drought in Ethiopia
causes
Ethiopia relies on two periods of rain throughout the year, one longer than the other
since the 1980s, the short rain season has been getting shorter and increasingly delayed and the long rain season has become equally unpredictable
a likely cause is the warming of the Indian ocean, where rising air loses moisture as rainfall. dryer air then moves westward and descends over Africa, causing drought
impacts
85% of the population lives in the countryside and depend on farming, and are the most vulnerable to climate change
farmers - unreliable rains make planning very difficult. harder to know when to plant and some types of crop they have used for generations no longer do well. livestock farmers - when land becomes too dry to support vegetation, there is less food and water for their animals
homes - people in rural areas rely on local plants and trees for building materials e.g. timber (houses) and grass (thatched roofs). drought reduces their availability or increases cost
food prices - less food means prices rise, particularly affecting the poorest and marginal people. this can lead to hunger and malnutrition and in the past has caused famine
water supplies - only 57% of Ethiopians have access to an improved water source - others rely on natural sources such as springs, rivers and lakes. when these dry up, people have to walk many kilometres to find water, particularly affecting elderly who cannot make the journey and women and children who do. the time spent fetching water takes children out of school and prevents women from working
health - water sources can also become polluted so people have no alternative but to use unsafe water, with the risk of diseases such as cholera, typhoid, dysentery and others. without access to medical care, these can be fatal
is also a cause of rural-urban migration
1983-present
Ethiopia a developing country in Africa
cycle of drought and famine still continuing with worse periods and less severe periods
responses
issues created by the drought brought to global attention in the 1980s through a large charity event called 'Live Aid'. this event was organised to make people more aware of the crisis caused by the drought and to try to raise money for the people affected
today, Ethiopia is developing rapidly and in times of hardship the govt. organises its own relief programmes
NGOs from around the world often work with Ethiopian experts in remote areas of the country to support those worse affected by drought. as the cycle of drought has continued, NGOs have been working to provide clean water, food and medical care for people affected by the droughts and food shortages. longer term, they also work with people to help them become more resilient to drought in the future e.g. by developing new farming techniques and crop varieties and improving access to safe water, education and training
a.
since water is such a valuable and necessary resource, droughts are extremely problematic
social impacts include: ill health/health risks, safety risks due to fires
economic impacts include: industries e.g. farming and other related industries unable to support jobs -> unemployment, loss of livelihood for farmers, food prices increase, water companies having to spend money on new supplies and pipes - leading to price rises
environmental impacts include: wild animals suffer with a lack of water, habitats damaged or lost, soil becomes dry so can no longer support plants, endangered species becoming extinct, forest fires - CO2 + damage to wildlife