Climatic Hazards

HideShow resource information

Causes and effects of tropical storms and hurrican

Tropical storms= winds of 64-118k/h  Hurricanes: Winds of over 118km/h

Conditions for:

  • Intense tropical depressions
  • Seasonal: June-November in northern hemisphere

Formation

  • High humidity releases latent heat
  • Sea temperature of more than 26-27'C for at least 60m depth
  • More than 5' north or south of Equator for Coriolis effect to impart spin
  • Almost constant vertical conditions
  • Divergent airflow with height to draw air upwards
  • Unstable air- surface winds converge
  • Two moist tropical airstreams meet and denser one undercuts the other
1 of 71

Formation of a hurricane

1. Warm ocean water (above 27'C) causes a large amount of water evaporation. The depth of water should be about 60m, so that cold water is not stirred up by the storm

2. Winds converge close to the ocean's surface, forcing air upwards

3. The winds rise rapidly because of the unstable air, triggering thunderstorms

4. Warm rising air condenses to form storm clouds and rain. The heat generated from water vapour condensing to form rain heats the surrounding air, causing it to rise

5. High pressure in the upper atmosphere removes heat from the rising air, which pulls warm air up from below

6. Wind speeds at all altitudes and wind direction must be consistent to prevent the storm breaking up and weakening

2 of 71

Development and characteristics

Development

  • Move westward due to Earth's rotation - 15-30km/h
  • Continue to grow as condensation releases heat energy picks up warmth from the sea
  • Break up over land (friction and little moisture) or as they move out of tropics 35'N/S as sea gets cooler

Characteristics

  • Central clear 'eye' of descending air
  • Around eye, massive cloud walls with rapid uplift
  • 12km high, 200-500km in diameter
  • High volume rainfall - up to 500mm in 24hrs
  • Very low air pressure- 900mb
  • Eye wall dominated by intense thunderstorms
  • Movement difficult to predict
3 of 71

Impacts from tropical storms and hurricanes

Impacts from:

  • Wind, storm surge, intense high rainfall, lightning

Types of impact

  • Primary- homes destroyed, deaths and injuries from flying debris
  • Secondary- flooding, pollution (sewage/drains etc), disease, hunger, fires (power lines down), transport disrupted
  • Tertiary- long-term economic impacts (e.g. cost, destruction of infrastructure, loss of jobs,etc)
4 of 71

Impacts

Environmental impacts

  • Relief- landslides, mudflows
  • Drainage- waterlogging, floods
  • Vegetation- trees destroyed/uprooted, habitats destroyed
  • Pollution of water supplies, disease

Social impacts

  • Health- injuries and death, disease, depression
  • Housing- destroyed, temporary shelter, forced to migrate
  • Social unrest- looting, family break up, tension

Economic impacts

  • Infrastructure- destroyed (e.g. roads, power, schools)
  • Agriculture- cash and food crops lost, pollution, tree crops hit hard
  • Transport- bridges destroyed, road and rail damage, loss of aeroplanes
  • Trade- loss of exports, need to import, cost of aid
5 of 71

Hurricane strength

Measured on the Saffir-Simpson scale:

Category 1: 120-53km/h, 980+mb, 1.5m storm surge, limited damage but flooding

Category 2: 154-77km/h 965-79mb, 2.0m storm surge, damge to roofs and vegetation

Category 3: 178-209km/h, 945-64mb, 3.0m storm surge, structural damage and storm surge

Category 4: 210-49km/h, 920-44mb, 3.0m storm surge, structural damage and mass evacuation

Category 5: 250+km/h, <920mb, >5.5m storm surge, Complete building failure and mass evacuation

6 of 71

Monitoring hurricanes

  • No known atmospheric conditions that automatically lead to hurricane formation
  • The National Hurricane Centre in Miami, Florida searches out potential hurricanes in their early stages and tracks them through their life cycle
  • Satellites detect hurricanes in their early stages of development and can help to provide early warning of imminent hurricanes- provide vital information about the location and movement of weather systems as well as information about the vertical structure and composition of the atmosphere
  • A combination of visible and infrared images is very useful
  • Reinforced aircraft fitted with instruments fly through and over hurricanes, and weather radar can locate storms within 200 miles of the radar station
7 of 71

Reducing the impact of Hurricane Katrina

Prediction- Proved very good but US National Oceanic and Atmospheric Administration (NOAA) is improving it by adding more weather buoys in the Gulf of Mexico

Risk assessment- Computer models gave a good assessment of areas at risk by 26th August

Prevention- Flood protection, levees in place

Planning-  60,000 National Guard troops mobilised on 26th August, Coast Guard at the ready

Warnings- Constant media warnings but mandatory evacuation order came only 19 hours before impact, 80% evacuated by much of the transport infrastructure shut down


8 of 71

Reducing the impact of Hurricane Katrina

Responses

  • Coast Guard rescued 35,000 people
  • Federal Emergency Management Agency (FEMA) put in 28 search and rescue teams, supplied 85 million litres of water and 50 million meals, and rehoused 700,000 in trailers 
  • Red Cross supplied 68 million meals and shelter for 1.4 million families
  • Salvation Army set up 178 canteen units and gave emotional and spiritual aid to 277,000 people

Recovery100m3 of debris removed and 2414km of channels cleared, over 1 million housed out of the area

Redevelopment-  US Army Corps has reinforced and raised 354km of levees FEMA given US$5.5 billion to rebuild public infrastructure and government $17 billion for rebuilding

9 of 71

Cyclone Rusty- Australia 2013

  • Duration: 18th February – 28th February
  • Winds of at least 230km/h
  • Cloud temperatures colder than -52C surrounding the eye of the storm
  • Thunderstorms in Rusty’s eye reported to have reached heights of over 12km (7 miles)
  • Recorded rainfall of over 138mm per hour near Rusty’s western side
  • Affected 1.6 million people

Timeline

  • On 18th February a tropical low formed over the Arafura Sea
  • 22nd February the tropical low moved into the area of responsibility of TCWC Perth
  • 24th February, the low reached Tropical Cyclone strength and was named Rusty
  • Cyclone watch declared for a large area of the Pilbara/Kimberley coastline between Broomeand Mardie extending to Marble Bar
  • Rusty remained relatively stationary off the Western Australian coastline reaching category 4 strength on 27th February with winds gusting to 230km/h
  • Rusty made landfall on 27th February near Pardoo, 100km East of Port Hedland
10 of 71

Cyclone Rusty- Australia 2013

Impacts

  • The effects of Rusty are far reaching, with areas of Southern WA and the Goldfields experiencing heavy rains, the city of Kalgoorlie-Boulder and the surrounding areas had non-stop rains for over 15 hours.
  • The Department of Fire and Emergency Services warned there was a possible threat to lives and homes in Marble Bar, Nullagine and De Grey Station because of rising rivers and streams.
  • Residents near the Yule and Turner river catchments near Port Hedland prepared for flooding.
  • The bureau’s Neil Bennett said a 3.5m to 4m storm surge was predicted, which could have increased to 10m if Rusty crossed high tide at midday.
  • The Pilbara region, close to where Rusty has hit, is the world's largest source of Iron Ore. Residents in the area prepared to be locked indoors for a few days waiting for the storm to pass over.
  • 600mm of rain fell in 24 hours (UK averages around 900mm of rain per year)
11 of 71

Tornadoes

= Violent rotating small-scale wind storms - can reach 500km/h

Conditions for formation

  • Seasonal: June-November in northern hemisphere
  • Often a remnant of a tropical storm

Formation

  • Air masses of differing temperature and humidity meet
  • Anvil thunderclouds, known as supercells, exist
  • Downward rapid current of cool air
  • Almost constant vertical conditions
  • Divergent airflow with height to draw air upwards
  • Very unstable air - surface winds converge or very hot surfaces
  • Flat land, as easily disrupted by relief
12 of 71

Development and characteristics of tornadoes

Development

  • Continue to grow as condensation releases latent heat energy
  • Break up over land (due to friction and little moisture) or where land is cooler

Characteristics

  • Small and short lived (rarely over an hour) but highly destructive
  • Elongated funnel of cloud (vortex) in contact with cloud and ground
  • 200m in diameter
  • High volume rainfall
  • Twisting wind rotation so lifts objects
  • Very steep pressure gradient (25mb per 100m)- centre is at very low pressure- pressure difference so great that many buildings 'explode'
  • Movement difficult to predict but tend to follow certain routes (e.g. tornado alley in Kansas)
13 of 71

Tornado strength

Measured using the Fujita scale

Category 0 - 117km/h, light damage (e.g. trees blown over)

Category 1- 117-80km/h, Moderate damage (e.g. moving cars blown over)

Category 2- 181-253km/h, Considerable damage (e.g. roofs torn off)

Category 3- 245-332km/h, Severe damage (e.g. parked cars lifted)

Category 4- 333-418km/h, Devastating damage (e.g. houses levelled)

Category 5- 419-512km/h, Incredible damage (e.g. houses blown away

14 of 71

Types of impacts

Primary- destruction of buildings, crops, deaths

Secondary- cost of rescue, loss of power, depression

Tertiary- long term economic impacts, e.g. cost, loss of jobs, etc

15 of 71

Impacts of tornadoes

Environmental impacts

  • Drainage- choked with wind-blown debris
  • Vegetation- trees destroyed/uprooted, habitats destroyed
  • Pollution of water supplies - disease

Social impacts

  • Health- injuries and deaths, disease, depression
  • Housing - destroyed, temporary shelter
  • Social unrest- looting

Economic impacts

  • Infrastructure- destroyed e.g. roads, power, schools
  • Agriculture- cash and food crops lost, pollution, tree crops hit hard
  • Transport- bridges destroyed, road and rail damage, loss of aeroplanes
  • Cost of aid
  • Industrial capacity reduced- damaged buildings, loss of power etc
16 of 71

Indiana tornado, November 2005

Characteristics

  • Developed along a squall line along a cold front
  • 4 tornados formed into 2 supercells
  •  Cut a swathe of damage 400m wide and 66km long
  •  Wind speeds reached 320km/h It lasted 10 hours
  • Unusual, as it occurred in November (most are June-March)  and at 1.50am (most occur during the day)

Impacts

  • 25 killed and 230 injured
  • US$92 million of damage
  • Gas leaks
  •  25,000 left without power
  • 225 mobile homes destroyed
17 of 71

Indiana tornado, November 2005

Responses

  • Rescue services were on site very quickly, as they were prepared
  • US$2.4 million of state aid made quickly available for housing etc
  • Long-term grants for rebuilding
18 of 71

High pressure systems: anticyclones

Characteristics:

  • Large area of slow-moving air
  • High pressure, as air is sinking
  • As air sinks it warms, causing temperature inversion
  • As air is sinking it can't rise to form clouds so there are clear skies
  • Winds are light, as gentle pressure gradient
  • Winds blow outwards, usually clockwise, in the northern hemisphere
  • Usually ends when uplift overcomes temperature inversion, leading to thunderstorms
19 of 71

Summer weather associated with high pressure

Temperature- Hot all day, Chilly at night, as no cloud to trap heat

Cloud- little but cumulus may form during the day

Precipitation- low- drought but may end with thunderstorm

Wind- Little - mostly calm

Sunshine - long hours of sunshine = heat stroke

Humidity- Varies with source of air, e.g. if tropical then very humid

Visibility- Mist in the early morning or over the colder sea, combined with heat haze, reduces visibility

20 of 71

Winter weather associated with high pressure

Cold in day, freezing at night = penetrating frost, Cold Spells

Little cloud

Very low precipitation as it is so cold, but if it warms snow can occur

Little wind- calm but if it blows then intense wind chill

Long hours of sunshine but if fog gets trapped under inversion layer it leads to anticyclonic gloom

low humidity = dry conditions

Fog common, especially along coasts near warmer sea or collecting in hollows

21 of 71

Low pressure systems: depressions

These develop along the polar front where cold northerly air meets/undercuts warm tropical air moving north. Depressions form as waves along this front.

Characteristics

  • Relatively small area of fast-moving air
  • Low pressure, as air is rising
  • Tend to move west to east across the UK
  • As air is rising it forms clouds, so bringing rain
  • Winds are strong, as steep pressure gradient
  • Winds blow inwards, usually anticlockwise, in the northern hemisphere
  • Rarely last more than a day but frequently one in a stream of depressions
  • Depressions have cold and warm fronts, as the warm air is undercut by the cold
22 of 71

Summer weather associated with low pressure

Temperature- Mild in the day, warm at night as cloud traps in heat

Cloud- heavy especially at the fronts

Precipitation- high- often heavy thunderstorm producing intense downpours

Wind- strong and gusty

Sunshine- relatively little sunshine

Humidity- high as warm air holds a lot of moisture

Visibility- Good but poor in rain and can cause hill fog as clouds are level with summits. Also frontal fog where air masses meet

23 of 71

Winter weather associated with low pressure

Temperature- Mild in the day, warm at night as cloud traps heat. No frost

Cloud- heavy especially at the fronts

Precipitation- high- usually rain but can be snow over hills. With strong winds this causes blizzards

Wind- strong and gusty so can cause wind chill

Sunshine- little sunshine- very dull and gloomy

Humidity- High as warm air holds a lot of moisture

Visibility- Good but hill fog common

24 of 71

European drought 2003

  • A drought is 15 consecutive days without rain
  • The 2003 drought lasted from February to October

Causes-  A series of intense anticyclones (blocking highs) that forced depressions north or south of the UK

Nature of the hazards

  • Lowest rainfall since 1921 and in August-October 77% below average
  • Evaporation 15% above normal
  • High temperatures (37 degrees recorded)
  • Thunderstorms and electrical storms, as the air was so dry
25 of 71

European drought 2003

Impacts

  •  High levels of pollution, high pollen count (hay fever) and danger of sunstroke and skin cancer
  •  Expansion of tourism (4%+) mainly to the cooler coast
  • Retailers expanded sales of beer, ice cream etc 
  •  900 deaths from poor air quality (high levels of ozone) 
  • Loss of work days- people took time off (estimated cost of £10 million a day)
  • Harvest yield fell 20% and milk yield fell 15% 
  • Water shortage so hosepipe bans
  • Roads melted in Essex, rails buckled
  • Subsidence in buildings as ground dried up and shrank
  • Trees hit hard- wilted and died
  • Reservoirs dried up (50% below capacity)- standpipes needed in driest areas
  • Fires, as the land was so dry (e.g. rare birds wiped out on Dorset heaths) 
  • Water-using industries were hard hit e.g. swimming pools, golf
  • Increased eutrophication (and fish deaths) in East Anglia
26 of 71

Drought management in Chad

Causes

  • Chad is hot and dry on account of its location relative to the heat equator
  •  High pressure Sahel area
  •  Inland
  • Desertification – bush felling and overgrazing with goats
  • Commercialisation of farming (e.g. cotton, which needs water for irrigation)

Water development possibilities

  • Water transfers but high cost and huge water loss- long distance transfers or inter-basin transfers
  • New dams- cost and where?
  • Desalinisation
  • Using icebergs as a source of fresh water
  • Develop groundwater sources- limited and will lower water table
  • Re-use effluent and recycle grey water
27 of 71

Drought management in Chad

Management

  • Reduce water losses – cover aqueducts etc
  • Increase cost of water
  • Ration water
  • Reduce water use (e.g. dryland farming, drought-resistant animals, etc)
  • Better technology (e.g. irrigation of individual plants)
  • Low level technology (e.g. walls of stones to slow runoff) 
  • The use of meters in people’s homes
  • Repairing leaking pipes
  • New technology such as desalinisation
28 of 71

North American Blizzard, February 2003

  •  Hit the east coast, especially Boston and Washington and lasted 5 days

Cause-  A blocking high pressure system over Canada forced air from Rockies (PC air mass) to cross the cold interior but then it met the moist warmer air of the coast

Nature of the hazards

  •  Snow 40-60cm deep- Blizzards (in Boston 70cm snow fell but in massive drifts)
  • Very low temperature and wind chill75km/h winds

Impacts

  • 27 deaths (car and other accidents and elderly deaths)
  • Transport paralysed- airports, rail and road links shut
  • Major power cuts as lines brought down- 95,000 homes blacked out in West Virginia
  • Schools closed for a week
  •  Some damage to buildings from weight of snow- cost US$14million 
  • High cost of clearing snow (eg. US$20million in New York)
29 of 71

Australian fires January 2013

  • Heatwave began on 27th December and lasted 8 days- widest spread heatwave in 80 years
  • Sydney went from sweltering record breaking highs of over 45’C to below average temperatures in the space of 10 minutes
  • Tasmania experienced peak temperature of 41.8'C on 4th January
  • Wind gusts of up to 100km/h swept through Sydney
  • Record-breaking temperature of 45.8’C recorded at Sydney’s Observatory Hill at 2.55pm
  • Heat-related illness Ambulance crews busier than usual
  • Transport meltdowns, melting roads and ice rinks
  • On 4th January, the ambulance service of NSW had responded to 93 cases of heat exposure and 133 people fainted and 37 people were treated for vomiting 
  • In western Sydney, the Australia Youth Olympics were postponed
  • Most trains across the CityRail network were delayed due to problems with overhead wiring and signalling
  • 20km section of Bells Line road started to melt
  • Scorching heat caused dry conditions
  • At least 100 homes destroyed in Dunalley by fires
  • Millions of dollars of property lost
  • Boats were sent to rescue people from the smoke
30 of 71

Air masses

These are large bodies of air with fairly uniform conditions. They are named on the basis of:

  • Their origin in high pressue source areas: polar (from high latitudes) Arctic (from the Arctic), tropical (from the tropics)
  • What they have travelled over: maritime (ocean), continental (land)
31 of 71

Polar maritime

  • Cool, dry and stable air mass at origin but picks up moisture over warm sea and becomes more unstable
  • Air comes from the high latitudes over the Pacific and Atlantic oceans and is essentially cool, moist and relatively unstable in the lower layers
  • It gives dull wet weather
  • The dominant air mass for the British Isles- 80%
  • Brings cloudy, cool, wet weather
32 of 71

Tropical maritime (Tm)

  • Warm, moist and unstable at origin but becomes more stable as it move north over cooler sea
  • Tends to occur in the summer in the British Isles making it very humid and if forced to rise it brings thunderstorms
  • Air comes from the oceans of the lower latitudes
  • It is warm, moist and unstable, especially in summer when convectional heating causes cooling of the air
33 of 71

Tropical continental (Tc)

  • Warm, dry and unstable at origin and rarely changes as it moves north in summer over warm dry land
  • Brings poor visibility (Saharan dust) and fog over the sea but little rain to the British Isles
  • Brings very hot weather to the UK
  • Air masses originate over hot deserts
34 of 71

Polar continental

  • Originate over central Canada and Siberia
  • At origin it is cold, dry and stable and this increases as it crosses cold land in winter
  • If it comes from north-east it crosses the North Sea, which warms it and adds moisture
  • It brings bitter cold winds to the British Isles causing very low temperatures and if it crosses the North Sea it can bring heavy snow to east coast and fog over sea
35 of 71

Arctic Maritime

  • Very cold, dry and stable at origin but becomes wetter and less stable as it moves south over the sea
  • Brings heavy snowfalls and bitter wind chills
36 of 71

Anticyclone environmental hazards

Ecosystems- Drought, fires, heat, frost

Vegetation

  • Trees susceptible to drought (lose their leaves)
  • Frost kills seedlings and buds (can't reproduce)
  • Trees wilt in heat, as increased transpiration means they need more water

Drainage

  • Bakes ground in drought so flash floods when it rains
  • Rivers and lakes dry up

Soils- Dry and shrink = subsidence

37 of 71

Anticyclone social and economic hazards

Social

  • Health
    • Poor due to heat/cold/fog and high pollen count
    • Heat stroke
  • Housing- heat and cold damage the fabric
  • Accidents- frost and fog cause poor driving conditions

Economic

  • Agriculture- Need to irrigate, frost kills crops
  • Forestry- Fires, droughts
  • Transport- Accidents in fog and on frost, heat buckles rails and melts roads
  • Industry- water shortage
  • Power- water shortage
38 of 71

Hazards brought by depressions

Environmental

  • Ecosystems- flooding, gales and storms
  • Vegetation- lack of sun, trees blown down
  • Drainage- flooding, waterlogging
  • Soils- swell = landslides, creep, soil erosion

Social

  • Health- dampness= bronchitis and depression
  • Housing- wind can damage housing (e.g. roofs)
  • Accidents- Wet roads and flooding, gales

Economic

  • Agriculture- lack of sun, waterlogging of crops, wind damage
  • Forestry- waterlogging, gales
  • Transport- wet surfaces= aquaplaning, strong winds halt flights and shut bridges
  • Industry- Gales and flooding. Gales bring down power lines
39 of 71

Hazards and their causes

Heavy snowfall and blizzards= arctic maritime and polar continental North Sea track, depression following prolonged anticyclone in winter

Frost= polar continental, anticyclone in winter, cold spells

Fog= anticyclones especially in autumn, polar air masses in summer over the warm land and over sea in winter, tropical over sea in summer

Drought= tropical continental, anticyclone

Heatwaves= tropical air mass, anticyclone in summer

Thunderstorms and heavy rain= tropical maritime, depression

Gales= depression

40 of 71

Factors influencing the severity of impacts

  • Time of day/season, how long it lasts
  • Scale: size of area it covers
  • Strength: the more extreme, the greater the impact
  • Frequency: is it common or rare and thus unexpected?
  • Awareness of population: warnings, communications, are people prepared?
  • Precautons taken: long term planning and short term measures
41 of 71

Impacts of climatic hazards vary over time

  • Level of development/technology
  • Duration
  • Recurrance interval and frequency of event
  • time of day/season/year
  • Build-up of events - warning interval
42 of 71

Impacts vary with location

  • Coastal versus inland
  • Ability to predict or forecast (level of technology)
  • Population density, distribution, level of perception and education
  • Level of communications - warning, mobility of population
  • Highland versus lowland
  • Urban versus ural
  • Level of development - building type, ability to warn / evactuate
  • Remoteness
  • Type and size (power) of hazard or mix of hazards
  • West versus east (depressions move west to east in the northern hemisphere) or north versus south (hurricanes die out as they move north and cool down)
43 of 71

Impact at different ends of development continuum

  • Tropical storms and droughts have the greatest impact in poorer countries
  • Poorer countries are particularly vulnerable because they are less well prepared to cope with natural hazards
  • Widespread poverty means that most individuals lack the resources and economic entitlements to buffer against natural disasters
44 of 71

Impact at different ends of development continuum-

  • Hurricane Katrina caused massive economic damage in the USA in 2005 (US$90 billion) and showed that even the richest countries are not immune to natural disasters
  • The death toll - 1,400 - was relatively low
    • Due to the effective hazard mitigation which reduced the vulnerability of the population of the Gulf states
    • Included advance warning of the hurricanes approach, evacuation strategies, disaster planning and the construction of maintenance levees
    • This level of disaster mitigation is costly and confined to wealthy countries
    • Evacuation is easier in a countries where most people own cars, telecommunications are universal and the road network is modern and efficient
45 of 71

Impact at different ends of development continuum-

  • In May 2008, Cyclone Nargis hit Myanmar, one of the poorest countries in Asia
  • A storm surge, similar to Katrina's, killed 140,000 people and either destroyed or damaged 800,000 homes
  • The human cost of this disaster was far greater than Hurricane Katrina
  • Most people hit by the disaster were poor farmers, who lost their crops and livestock and lacked the resources to survive without emergency relief aid
  • Cyclone Nargis highlighted Myanmar's vulnerabiity to storm surges, especially in the densely populated Irrawaddy Delta
  • Its impact was increased by poorly maintained levees along the coast, a lack of coastal radar to estimate the height of storm surges and the failure of the government to provide warning until 24 hours before the storm made landfall
46 of 71

Impact at different ends of development continuum-

  • Drought has a much greater human and economic impact in poorer countries
  • In 2005, the drought in southern Spain was the worst in 60 years
    • It caused severe water shortages which damaged tourism and agriculture, lowered water tables and triggered wildfires
    • The losses suffered by agriculture were 2-3 billion euros
  • Even so, in rich countries the impact of drought can easiery be absorbed and for many might be little more than an inconvenience
  • In poor countries, where most people rely heavily on subsistence and semi-subsistence farming, the human cost of drought can be devestating
    • Water holes dry up, animals die and crops fail
    • Indigenous people face food shortages and famine
  • In the summer of 2005, in southern Niger, drought reduced the grain harvest by a quarter, bringing famine to 3 million people
    • Despite international relief aid, thousands died from starvation and disease
    • 
47 of 71

Impacts in urban and rural areas

  • The impact of extreme weather events such as heatwaves often varies between urban and rural areas
  • Urban microclimates are warmer than those in rural areas because:
    • Building materials such as brick, tarmac and concrete store heat in the day and release it at night
    • Air pollution helps to keep heat in
    • There is less vegetation to cool the atmosphere
    • Cities produce heat (motor vehicles, space heating etc)
48 of 71

Impacts in urban and rural areas- examples

  • In July and August 2003 an exceptional heatwave struck western europe
  • It raised mortality rates sharply in large urban areas, where temperatures were several degrees higher than in the countryside
  • The heatwave caused 15,000 deaths in France, with around 1/3 in the Paris region alone
  • Rural areas, dependent on agriculture, are more likely to suffer economically in a prolonged heatwave (accompanied by drought) because of reductions in crop yields
    • The 2003 heatwave badly affected wheat yields, which were 13% below average in Italy and 20% below average in France
    • 
49 of 71

Impacts in urban and rural areas- examples

  • Rural areas are often more badly affected by tropical storms
  • This is partly because it is more difficult to access survivors and provide emergency aid
  • Bridges and roads, destroyed by floods and landslides, may leave many rural communities isolated in the days immediately after a storm disaster - and without food, clean water and medical supplies
  • Rural economies, dependent on farming are more vulnerable to climatic hazards than urban economies, and urban populations are on the whole better off than rural populations, therefore more resilient in the face of climatic hazards and disasters
50 of 71

Impacts in coastal and inland areas

  • Coastal regions in the tropics and sub-tropics are exposed to tropical storm hazards
    • Partly explained by the nature of tropical storms, which originate over the ocean and derive their energy from warm surface waters
    • Once tropical storms make landfall, they quickly lose their energy
  • Coastal regions are also, by definition, at or near sea level and so at particular risk from storm surges generated by tropical storms
  • Coastal areas tend on average to be more densely populated than inland areas, further increasing their exposure to tropical storms and other climatic hazards

In contrast:

  • Exceptional rainfall events that trigger mass movements are more likely to occur inland, and especially in mountainous regions where rainfall is intense and slopes are steep and often unstable
  • Much of the destruction associated with Hurricane Mitch in Central America, 1998, was the result of mudflows and mudslides in the mountains
51 of 71

Impacts in coastal and inland areas- examples

  • In the UK, blizzard conditions occur more often inland than on the coast- two reasons:
    • Mountainous regions like the Scottish highlands increase precipitation through uplift and experience higher average wind speeds than lowland areas
    • Coastal areas experience milder conditions in winter, when sea surface temperatures are 2 or 3'C higher than those over land
  • Although tornadoes can occur over the sea, they are more common and powerful in central continental areas like the US Midwest- explanation due to tornado formation
    • Humid warm airmass that develops over the ocean and tracks inland
    • A dry, cool airmass of continental origin
    • The convergence of these two contrasting airmasses most often occurs in continental locations hundreds of miles from the coast
52 of 71

Impacts vary over short and long time periods

  • The immediate impacts of natural hazards such as tropical storms and droughts create emergency situations such as food shortages, lack of clean water and the need for urgent medical treatment and temporary shelter
  • Resources to address these problems are provided by disaster relief agencies such as the Red Cross and the Federal Emergency Management Agency (FEMA), non-governmental organisations (NGOs) like Oxfam, and multilateral organisations (e.g. the UN)
  • Governments focus initially on meeting essential needs and protecting life
    • The drought and subsequent famine in Niger 2005, the priority was food aid, clean water and medicines
    • In the Hurricane Katrina disaster, the immediate need of the victims of flooding in New Orleans was accommodation. Thousands were housed temporarily in the city's Convention Centre and in the Louisiana Sports Dome
53 of 71

Impacts vary over short and long time periods

  • Natural disasters also have long-term effects- economies need to be reconstructed, infrastructure rebuilt and jobs provided
    • In New Orleans a decision has still to be made about the future of some low-lying suburbs several metres below sea level
    • Meanwhile, long-term reconstruction is underway- Levees high enough to withstand storm surges generated by category 5 hurricanes have been constructed and new pumping stations are being built
    • 4 years after the disaster, thousand of people had still not returned to their homes
  • The long-term impact of severe drought in sub-saharan Africa is often permanent land degration and the destruction of pasture, water and soil resources, which once sustained whole communities
    • In extreme cases, farmers are forced to abandon the land and head for the nearest city
    • For those farming communities that remain viable, the legacy of drought might be long term aid in the form of tube wells to guarantee water supplies, irrigation schemes and expert education and advice on sustainable methods of farming
    • Most of these initiatives will be supported by international aid
54 of 71

Measures used to reduce impacts

Prediction- based on past events (hazard mapping), monitoring of pressure, satellites, weather balloons, etc.

Risk assessment- calculate size and extent of risk, inform population, adapt building design and location of vital buildings/facilities (e.g. power stations)

Prevention- seed depressions/hurricanes, afforest slopes, raise and strengthen levees, build reservoirs, modify channels, move vulnerable population and livestock, establish exclusion zones, remove dangerous objects e.g. signs

Planning- individual e.g. store water, local authority (e.g. emergency centres or shelters), state or central (e.g. mobilsation of rescue services), building controls

Preparation- education (emergency drills), contingency plans (e.g. evacuation routes signposted, training of emergency staff, etc)

Warnings - use of media, communications, level of threat, planning evacuations

55 of 71

Measures used to reduce impacts

Prevention during event- dam or divert rivers, stabilise slopes, pass laws to force evacuation or water saving (e.g. hosepipe bans), rationing, etc

Responses- Search and rescue, emergency aid, insurance, state or international aid for rescue and relocation

Recovery- clearance of debris, state aid for reconstruction, tax relief

Redevelopment- long-term plans

56 of 71

Reducing impacts

  • Some hazards are easier to predict than others
  • While improvements in evacuation procedures and emergency aid can save many lives from climatic hazard, it is harder to mitigate the immense economic impact
  • One of the best ways of reducing hurricane impact is to maintain a complete cover of coastal forest e.g. been successfully done in parts of Dover Beach, Barbados, this reduces strength of the wind, and the vegetation slows down the force and height of the surge
  • One way of reducing the economic cost of hurricanes would be through better planning of human settlement, avoiding rickiest areas- but many countries authorities have no powers to prevent building
  • There is scope to mitigate the economic impact of disasters through making sure people have access to money to help them rebuild their lives and businesses
57 of 71

Physical and social adjustments to hazards

Physical

  • Altering characteristics of hazards (e.g. attempts have been made to seed clouds to reduce hurricane energy)
  • Building to withstand hazards (e.g. hurricane shelters in Florida)
  • Constructing diversions, barriers, etc (e.g. planting trees as windbreaks)
  • Moving people to less vulnerable locations (e.g. away from low-lying areas of New Orleans)

Social

  • Increasing public awareness via education, media, etc (e.g. tornado training for schoolchildren in the American Mid-West)
  • Making local evacuation plans and preparations (e.g. use of radio and village communication systems in Bangladesh when a tropical storm approaches)
  • Greater community involvement to reduce vulnerability (e.g. Neighbourhood Watch systems in UK to look out for elderly in cold spells)
58 of 71

Political adjustments to hazards

  • Emphasising evacuation plans, services and emergency centres (e.g. these were increased in the Gulf of Mexico following Katrina)
  • Land use zoning and restrictions (e.g. along the Mississippi in New Orleans following Katrina)
  • Issuing early warnings and coordinating emergency services (e.g. hurricane preparation in south-east USA)
  • Spreading economic loss via insurance, grants etc (e.g. US goverment in New Orleans following Katrina)
59 of 71

Managing climatic hazards

Depends upon:

  • The nature of the hazard - its severity, scale, frequency, any build-up signs etc
  • The level of preparation and awareness of risks
  • The nature of the area- its structure, geology, relief, climate etc
  • The level of development- research, technology available, communications, warnings
  • The nature of the population- density, education, mobility, level of perception etc
  • Political organisation - coordination, priority, existence of emergency plans etc
60 of 71

Managing water supplies

Approximately 25% of the world's surface experiences a shortage in water, can be sourced in many ways:

  • extraction from rivers and lakes
  • trapping behind dams and banks
  • pumping from aquifiers
  • desalinisation

'water harvesting' is making use of avaliable water before it drains away or evaporates. It can be achieved in many ways:

  • irrigation of individual plants rather than of whole fields
  • covering expanses of water with plastic or chemicals to reduce evaporation
  • storage of water underground in gravel-filled reservoirs

Inappropriate use of water can lead to: salinisation (build up of toxic salts in the soil) and waterlogging (which produces cold, oxygen deficient conditions in soil and is useless for farming.

61 of 71

Global Warming

Greenhouse gases in the atmosphere trap the Earth's longwave radiation- a process known as enhanced greenhouse effect

Earth's temperature is predicted to rise by 1-6'C this century. Causes:

  • Burning fossil fuels produces carbon dioxide (which will have doubled between 1950-2050)
  • Transport producing carbon dioxide and nitrous oxide
  • Farming- cattle (emit 100 million tonnes of methane a year) Rice paddy fields producing methane and agrichemicals (e.g. fertilisers) releasing greenhouse gases
  • Deforestation- less carbon absorbed and often cleared by burning
  • Waste tips produce methane
  • Industry producing hydrofluorocarbons (increasing at 4% a year)
  • Melting permafrost releasing methane and carbon dioxide
62 of 71

Causes of global warming

  • Current rise in average global temperature is almost certainly due to human activity
    • increased levels of atmospheric carbon dioxide and other atmospheric gases
  • These gases which are largely transparent to incoming solar radiation, trap increasing amounts of long-wave radiation emitted by the Earth - a process called enhanced greenhouse effect - responsible for the steady rise in global temperatures
  • Several human activities input greenhouse gases to the atmosphere
    • Burning of fossil fuels which has increased massively in the past 50 years
    • Deforestation also releases large quantities of carbon dioxide that was previously stored as carbon in trees
63 of 71

Effects of global warming

  • Effects are wide-ranging and if unchecked could be disastrous for the biosphere and society
    • Climate change- climatic belts will shift polewards
      • Semi-arid regions like the Mediterranean and the continental tropical and temperate grasslands will become drier, making farming unsustainable meaning millions will be displaced
      • Heatwaves will occur more frequently bringing major health problems to large cities in mid-latitudes
      • In a warmer world, evaporation will increase and rainfall, violent storms and river flooding will become more common accelerating coastal erosion and flood risk
    • Many plants and animals will be unable to adjust leading to mass extinctions and a loss of biodiversity
      • species found in higher latitudes and in mountain habitats are most vulnerable
    • Many tropic diseases such as malaria and yellow fever are likely to diffuse polewards in warmer and more humid conditions
64 of 71

Effects of global warming

  • Rising temperatures are already causing ice sheets, glaciers and sea ice to melt at an alarming rate
    • As the ice retreats and exposes land and sea surfaces, positive feedback raises global temperatures even higher
    • The melting of land-based ice will raise sea levels by 2m+ by the end of the century
    • In developed countries coastal defences will have to be strengthened
    • In poor countries like Bangladesh, millions of people will become environmental refugees
    • Some island states such as the Maldives and Tuvalu which are barely above sea level today will be lost completely
    • Meanwhile, the melting of permafrost in the Arctic and sub-arctic could release catastrophic amounds of carbon dioxide and greatly speed up the rate of warming and sea level rise
    • Global warming could drastically change the thermohaline circulation and pattern of ocean currents, with potentially devastating impacts on regional climates
65 of 71

Causes and effects of global dimming

  • Global dimming describes the gradual reduction in the amount of solar radiation reaching the Earth's surface in recent decades
  • It is caused by tiny airbourne particles or aerosols released into the atmosphere by combustion. dust storms and volcanic eruptions
  • However, human activity through the burning of coal, and to a lesser degree, oil and gas is thought to be the main driver of global dimming
  • The effects of global dimming could be both positive and negative
    • It could reduce incoming solar radiation and therefore help to cool the planet
    • The negative effects include possible reduction in photosynthesis, plant growth and crop yields, especially in middle and higher latitudes
    • It is also suggested that global dimming could increase the incidence of drought, due to lower evaporation and disruption to the hydrological cycle
66 of 71

Causes and effects of acid rain

  • Emissions of sulphur dioxide, nitrogen oxides and ammonia from coal-fired power stations, motor vehicles and intensive farming pollute the atmosphere
  • Mixed with water droplets in clouds, they eventually return to the surface as acid rain
  • The principle effects of acid rain are:
    • The acidification of lakes, streams and the soil
    • The destruction of forests and wildlife habitats
    • The corrosion of buildings and stone monuments
  • Acidic soils are leached of essential nutrients, and toxic metals such as aluminium get into food chains and destroy aquatic life
    • Toxic soilds and dry acid deposition on foliage caused widespread destruction of coniferous forests in Europe in the 1970s and 1980s.
    • Acid rain also adversely affects human health and contributes to respiratory diseases such as bronchitis and asthma
67 of 71

Responses to acid rain

  • In Europe there has been concerted international response to acid rain problems and levels of acidity in rainfall have been significantly reduced
  • Binding emissions targets to be achieved by 2010 were set in the Goteborg Protocol
  • As a result of this and earlier incentives, emissions of sulphur dioxide and nitrogen oxides fell by almost 3/4 between 1980 and 2004
  • Liming of acidified lakes was adopted as a solution of last resort in Scandinavia, and in the short term also proved successful
  • Although the acid rain has been effectively tackled in Eurpoe, it remains a serious environmental problem in rapidly industrialising countries such as China and India, which rely heavily on coal-fired power stations or electricity
68 of 71

LEDC, smog in Indonesia

  • Affected an area larger than western Europe including Malaysia, the Philippines and Thailand-  70 million people affected

Causes

  •  Burning (often illegally) of forest and plantations to clear land cheaply and easily, often organised by TNCs
  • El Nino effect led to drought, which dried up the forests
  • High pressure so inversion layer trapped smog
  • Late arrival of monsoon so no rain to put out fires and clear the air
  • Weak and corrupt local government made it difficult to enforce anti-burning laws
  • Damage to rainforests made them easier to burn
  • Lack of alternative fuels for the poor
  • Inadequate fire-fighting resources
69 of 71

LEDC, smog in Indonesia

Short term impacts

  • Over 60,000 treated for smog-related illnesses and eye problems
  • Airliner crashed, killing 234; flights cancelled or rerouted
  • Ships re-routed to avoid straits of Malacca
  • Schools closed
  • Loss of tourism
  • Loss of expatriates

Long term

  • Over 275 died from starvation
  • Deaths from cholera due to lack of clean water
  • Crop yields fell and many areas had to import food
  • Added to global warming and reduced carbon dioxide-absorbing vegetation
  • Loss of biodiversity – species wiped out and food chain disrupted
  • Peat may burn for 20 years so seeds can’t germinate
70 of 71

LEDC, smog in Indonesia

Reactions

  • Put out fires, e.g. using cloud seeding, water bombers (from USA) and fire fighters from Australia
  • Stop fires being lit- companies found guilty of starting fires have their operating licences revoked
  • Develop industries other than timber and tree crops (palm oil particularly)
  • International cooperation – in 2000 ASEAN adopted a zero burning policy to solve the problem
71 of 71

Comments

Mr A Gibson

A great collection of over 70 revision cards which will give you the information you need to revise thoroughly units on Climatic Hazards. All about cause and effect, demonstrated through case studies, colour coded for ease of use, and loads of examples and facts/figures. get this onto your mobile device if you can, print them out if you can't!

Similar Geography resources:

See all Geography resources »See all Natural hazards resources »