Weather hazards Flashcards
1
Q
what is global atmospheric circulation?
A
the atmosphere- is a highly complex swirling mass of gases, liquids and solids. These include water droplets, water vapour, ash, carbon dioxide and oxygen…
2
Q
how does global atmospheric circulation work?
A
- air that is sinking towards the ground surface forms areas of high pressure (e.g north pole). winds on the ground move outwards from these areas.
- air that is rising from the ground surface forms areas of low pressure on the ground, e.g. at the Equator. winds on the ground move towards these areas of low pressure.
- winds on the ground are distorted by the Earth’s rotation, they curve as they move from areas of high pressure to areas of low pressure
- surface winds are very important in transfering heat and moisture from one place to another
- the patterns of pressure belts and winds are affected by seasonal changes. The tilt and rotation of the Earth causes relative changes in the position of the overhead sun. These seasonal changes cause pressure belts and winds to move north during our summer and neth south during our winter.
3
Q
How does global circulation affect the world’s weather?
A
Global atmospheric circulation is what drives the world’s weather. The circulation cells, pressure belts and surface winds affecr the weather around the world. For example, the trade winds in the tropics are responsible for driving tropical storms (hurricanes) across these regioons bringing chaos and destruction to coastal regions in their path.
4
Q
Cloudy and Wet in the UK
A
- located 55 degree North just below the 60 degree north line of latitude
- puts the Uk close to the boundary of cold pilar air moving down from the north and warm sub-tropical air moving up from the south.
- the boundary between these 2 air masses is unstable
- here there is rising air and low- pressure belts (the sub-polar low) on the ground.
- rising air cools, condenses and forms cloud and rain- this is why it is often cloudy and wet in the UK
- surface winds in these mid-latitudes come from the south west. These winds bring warm and wet conditions to the UK
- sometimes the cold polar air from the north moves down over the UK bringing snow and very cold winter weather.
5
Q
Hot and dry in the desert
A
- Most of the world’s hot deserts are fpund about 30 degree north and south of the equator
- here the air is sinking, making a belt of high pressure (sub- tropical high)
- As the air isn’t rising here there are few clouds forming and little rainfall
- the lack of cloud makes it very hot during the day whilst very cold in the night, as heat is quickly lost from the ground.
6
Q
Hot and sweaty at the equator
A
- At the Equator the air is rising and there is another low pressure belt (the equatorial low).
- this part of the world is very much hotter than the UK, with the sun directly overhead
- Equatorial regions, such as CENTRAL AFRICA and SOUTH-EAST ASIA, experience hot, humid conditions
- often cloudy with high rainfall
- this is the region where tropical rainforests are found.
7
Q
what is a tropical storm?
What are they called in different areas?
An example of a tropical storm?
A
it is a huge storm that develops in the region of the tropics
- In the USA and Caribbean- they are called hurricanes
- In south east Asia and Australia- they are called cyclones
- In Japan and the Phillipines- they are called cyclones
- Hurricane sandy - east coast of the USA in 2012
- 285 people died
8
Q
where do they form?
A
They form over warm oceans at 27 degrees or above- why they are often found in the tropics
- form in the months of summer and autumn- when the sea temperatures are at their highest
- mostly found 5-15 degrees north of the equator- not at the equator as there is not enough spin from the earth’s rotation there.
- CORIOLIS EFFECT- earth’s rotation
- they are spinning mass of clouds
- in tropical regions have itense heat and the air is unstable, so that air will rise rapidly
- this is important in the formation of hurricanes.
9
Q
how do they form?
A
- a strong upward movement of air draws water vapour up from the warm ocean surface (27 or above)
- this evaporated air cools as it rises and condenses to form towering thunderstorm clouds
- as the air condenses it releases heat which power the storm and draws up more and more water from the ocean
- several salle rhtunderstorms join together to form a giant spinning storm. when surface winds reach an average of 120km per hour (75 miles per hour) the storm officialy becomes a tropical storm
- the storm now develops an eye at its centre where air descends rapidly. The outer edge of the eye is the eyewall where the most intense weather conditions (strong winds and heavy rain) are felt.
- as the storm is carried across the ocean by the prevailing winds, it continues to gather strength
- on reaching land the storm’s energy supply (evaporated water) is cut off. Friction with the land slows it down and it begins to weaken. If the storm reaches warm seas after crossing the land, it may pick up strength again.
10
Q
what is the structure of a tropical storm?
A
tropical storms can be huge, up to 480km (300 miles) across. A tropical storm has a roughly symmetrical shape.
11
Q
will climate change affect tropical storms?
A
strong scientific evidence that global temperaturs have risen over the last few decades. These rises may be impacting on the world’s natural systems.
12
Q
Distribution
A
- over the last few decades sea surface temperatures in the Tropics have increased by 0.25-0.5 degrees celsius. As patterns of sea surface temperatures change, they may affecr the distribution of tropical storms.
- in the future, they may affect areas outside the current hazard zone, such as the South Atlantic and parts of the sub-tropics. Hurricanes may also become more powerful
13
Q
Hurricance Catrina- 2004
A
- March 2004
- South East coast of Brazil
- category 2 hurricane
- first ever recorded there
- coastal communities were taken by surprise and extensive damage was done- some people died, 40000 homes were damaged and 85 per cent of the region’s banana plants were destroyed.
- hurricanes do not usually form in the South Atlantic. - cold ocean currents keep waters below the minimum temperature required for hurricane formation. Strong winds ‘shear’ rising air preventing storms from forming
- in march 2004, sea surface temperatures were unusually high- conditions were right for a hurricane to form– events such as this may become more common as sea surface temperatures change.
14
Q
frequency of tropical storms
A
page 27 graph B -
In the North Atlantic since 1878
– six of the ten most active years since 1950 have happened since the mid-1990s
- some computer models indicate that the frequency of tropical storms may decrease in the future– however their intensity might increase.
15
Q
intensity -
A
Graph C page 27- hurricane intensity in the North Atlantic has risen in the last 20 yeats
- appears to be linked to increases in sea surface temperatures
- comparisons with the past may not be completely reliable, more data will be needed over a longer period of time
16
Q
typhoon haiyan
- what happened?
A
- November 2013
- ‘Super’ typhoon Haiyan- category 5 on the saffir simpson scale
- hit the phillipines
- huge areas of coastline and several towns were devastated by winds of up to 275km/h (170mph) and waves as high as 15m (45ft)
17
Q
what were the effects of Typhoon Haiyan
A
- province of Leyte took the full force of the storm
- city of Tacloban was one of the worst affected places– 220,000 inhabitants left homeless
- most of the destruction in Tacloban was caused by a 5- metre high storm surge- wall of water similar to a tsunami.
- low atmospheric pressure associated with the typhoon caused the level of the sea to rise- strong winds swept this water onshore, forming a wall of water several metres high
18
Q
primary effects of Typhoon Haiyan
A
- 6300 killed- most drowned in the sea surge
- over 600,000 displaced and 40,000 homes damaged or flattened
- 90% of Tacloban city destroyed
- Tacloban airport terminal badly damaged
- it destroted 30,000 fishing boats
- strong winds damaged buildings and power lines and destroyed crops
- over 400mm of rain caused widespread flooding
19
Q
secondary effects of Typhoon Haiyan
A
- 14 million people affected, many left homeless and 6 million people lost their source of income
- flooding caused landslides and blocked roads, cutting off aid to remote communities
- power supplies in some areas cut off for a month
- ferry services and airline flights disrupted for weeks, slowing down aid efforts
- shortages of water,food and shelter affected many people, leading to outbreaks of disease
- many jobs lost, hospitals were damaged, shops and schools were destroyed, affecting people’s livelihoods and education
- looting and violence broke out in Tacloban
20
Q
immediate responses - typhoon haiyan
A
- international government and aid agencies responded quickly with food aid, water and temporary shelters
- us aircraft carrier George Washington and helicopters assisted with search and rescue and delivery of aid
- over 1200 evacuation centres were set up to help the homeless
- UK government sent shelter kits, each on able to provide emergency shelter for a family
- French, Belgian and Israeli field hospitals set up to help the injured
- The Philippines Red Cross delivered basic food aid, which included rice, canned food, sugar, salt and cooking oil.
21
Q
long- term responses - Typhoon Haiyan
A
- The UN and countries including the UK, Australia, Japan and the US donated financial aid, supplies and medical support
- rebuilding of roads, bridges and airport facilities
- ‘cash for work’ programmes- people paid to help clear debris and rebuild the city
- foreign donors, including the US, Australia and the EU, supported new livelihood opportunities
- Rice farming and fishing quickly re-established. Coconut production- where trees may take five years to bear fruit- will take longer
- aid agencies such as Oxfam supported the replacement of fishing boats- a vital source of income
- thousands of homes have been built away form areas at risk from flooding
- more cyclone shelters built to accommodate people evacuated from coastal areas.
22
Q
What are the UK’s weather hazards?
A
Thunderstorms
- July 2014 dramatic electrical storm resulted in 3000 lightning strikes across southern Britain following a period of hot weather
- Torrential rainfall associated with thunderstorms can result in flash flooding- Boscastle in Cornwall in 2004
Prolonged rainfall
- persistent rainfall over a long period can lead to river floods– common in the UK especially during the late winter and early spring when snowmelt makes the problem worse
- During the very wet winter of 2014 flooding was widespread across southern England
Drought and extreme heat
- the UK has experienced long spells of dry, hot weather result in drought. Rivers can dry up and reservoirs become dangerously low– affect water supplies and wildlife
- very high temperatures - heatwaves- can be dangerous to elderly and frail people
- 2003, much of Europe sffered the most extreme heatwave of 500 years – over 20,000 people died.
- Several countries, including the UK, recorded their highest ever temperatures.
Heavy snow and extreme cold
- Long periods of severe winter weather have become less common n recent years, but there are occasions when heavy snow and severe cold can cause great hardship to people particularly in the north of the UK.
Strong winds
- The UK does occasionally get battered by strong winds. Sometimes the remnants of hurricanes travel over the Atlantic from the USA and Caribbean
- these can cause disruption to power supplies and damage form fallen trees
- strong winds hit the UK in Feb 2014
- 21,000 people without power
- electricity supplies were affected in South Wales, the south-west and the West Midlands
- wind speeds of up to 105mph were recorded in Aberdare in north-west Wales
- gusts of 92mph ion the Gower peninsula, south-west Wales.
- Clifton suspension bridge in Bristol closed briefly due to high winds and fallen trees.
23
Q
why does extreme weather occur in the UK?
A
The UK is rather like a roundabout (Map E page 33) because it is at the meeting point of several different types of weather form different directions. This explains why we experience such varied weather from week to week and how occasionally we can be affected b extreme weather events.
24
Q
Somerset Level floods- 2014
Where are the Somerset levels?
A
- county in south-west England
- The somerset Levels and the somerset Moors form an extensive area of low-lying farmland and wetlands bordered by the Bristol Channel and Quantock Hills to the west and the Mendip Hills to the North.
- area is drained by several rivers, most notably the Tone and the Parrett, which flow to the severn estuary via Bridgwater
- flooding has occurred naturally here for centuries
- as the area has been developed for farming and settlement, many people are now at risk from extreme flood events.
25
what caused the somerset level floods?
- wettest january since records began in 1910, a succession of depressions (areas of low pressure) driven across the Atlantic Ocean brought a period of wet weather, lasting several weeks
- About 350mm of rain fell in January ad February, about 100mm above average
- high tides and storm surges swept water up the rivers from the Bristol channel- prevented fresh water reaching the sea and it spilled over the river banks
- rivers had not been dredged for at least 20 years- clogged with sediment.
26
Impacts of the Somerset flood-
| Social
- over 600 houses flooded
- 16 farms evacuated
- residents evacuated to temporary accommodation for several months
- villages such as Moorland and Muchelney cut off - affected people's daily lives, e.g. attending school, shopping
- many people had power supplies cut off
27
economic problems- somerset level floods
- somerset county council estimated the cost of the flood damage to be more than £10 million
- over 14000 ha of agricultural land under water for 3-4 weeks
- over 1000 livestock evacuated
- local roads cut off by floods
- Bristol to Taunton railway line closed at Bridgwater
28
environment problems-
| Somerset level floods
- floodwaters were heavily contaminated with sewage and other pollutants including oil and chemicals
- a huge amount of debris had to be cleared
- stagnant water that had collected for months had to be deoxygenated before being pumped back into the rivers
29
immediate responses- Somerset floods
- As the floodwaters spread out over the Somerset Levels, homeowners coped as best they could.
- Villagers cut off by the floods used boats to go shopping or attend school. - Local community groups and volunteers gave invaluable support
30
longer- term responses - Somerset floods
- a £20 million flood Action Plan has been launched by Somerset County Council who will work together with agencies such as the Environment Agency to reduce the risk of future flooding
- In march 2014, 8km of the Rivers Tone and Parrattt were dredged to increase the capacity of the river channel.
- road levels have been raised in places to maintain communications and enable businesses to continue during future flood events
- vulnerable communities will have flood defences
- river banks are being raised and strengthened and more pumping stations will be built
- In the Longer term- by 2024- consideration will be given to a tidal bank at Bridgwater
* ** 1) silt is deposited on river bed
2) heavy rain causes river to food
3) diggers or pumps remove silt to build river banks and increase river capacity***
31
Evidence of extreme weather in the UK
Heatwave- 2003
- 38.5 degrees celsius in Kent
- over 2000 people died
- railway tracks buckled and in places roads melted
Floods- 2007
- several people died
- many left homeless
- summer floods affected Hull, Shefield and Gloustershire
Floods- 2008
- south-west and north-east England
- Somerset, Worcestershire and Northumberland
Heavy Snow- 2009
- parts of south-west and south-east England were affected by heavy snow with 20cm falling in the capital
Floods- 2009
- town of Cockermouth in Cumbria
- devastated bt floods
- record rainfall amounts fell in November in the Lake District
Heavy snow- 2010
- much of the UK was hit by heavy snowfalls in December
- Northern Ireland recorded a record low temperature of -18.7 degrees celsius at Castlederg
Floods- 2013/14
- severe flooding occured across southwen England
- River thames bursted its banks and vast areas of Somerset Levels to become inundated
- England's wettest winter in 250 years
Floods- 2015/16
- severe storms and exceptionally heavy rainfall caused devastating floods to many areas, especially the north of England.
- Yorkshire and Cumbria were badly affected
- December 2015 was the wettest and warmest month ever recorded in the UK
32
why might extreme weather events be on the increase?
- More energy in the atmosphere could lead to more intense storms-- global warming
- The atmosphere circulation may be affected, bringing floods to normally dry regions and heatwaves to normally cooler areas
33
Saffir- simpson scale
category 1:
- Wind speed: 74-95 mph, 64-82 kt, 119-153km/h
- Description: Very dangerous winds will produce some damage- e.g. to roof tiles or gutters
category 2:
- Wind speed: 96-110 mph, 83-95 kt, 154-177 km/h
- Description: extremely dangerous winds will cause extensive damage- .g. major roof damage
category 3:
- Wind speed: 111-129 mph, 96-112 kt, 178-208 km/h
- Description: devastating damage e.g. removal of decking, trees snap/uprooted- trees could block roads
category 4:
- Wind speed: 130-156 mph, 113-136kt, 209-251 km/h
- Description: catastrophic damage will occur e.g. loss of complete roof structure and maybe exterior walls- trees will also be uprooted
category 5:
wind speed: 157mph - / 137 kt - / 252 km/h -
description: high percentage of houses will be wiped out/destroyed, fallen trees/power poles. most of the area will be inhabitable, fallen power poles will cause isolation, little chance of survival for anyone within the storm itself
