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Geography > Weather Hazards 1 > Flashcards

Weather Hazards 1 Flashcards

Global atmospheric circulation, UK weather hazards, Somerset levels flooding

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1
Q

What is Global atmospheric circulation?

A

The transfer of heat from the equator to the poles by the movement of air.

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2
Q

Why does air move?

A

Due to differences in air pressure: winds blow from high pressure areas to low pressure areas.

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3
Q

Low pressure air

A

Warm rising air which condenses to form clouds, and so creates a wet climate.

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4
Q

Weather

A

The state of the atmosphere at a given time and place.

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5
Q

Climate

A

The long-term pattern of weather, based on an average over 30 years. For example , the average temperature or rainfall we’d expect each month.

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6
Q

The global atmospheric circulation system is divided into loops, called the…

A

Hadley, Ferrel, and Polar cells.

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7
Q

How are low pressure belts formed?

A

By warm rising air.

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8
Q

How are high pressure belts formed?

A

By cool sinking air.

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9
Q

How many cells does each hemisphere of the globe have?

A

3

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10
Q

What type of belt is found at the equator and why?

A

A low pressure belt, because the earth at the equator is heated by the sun, causing air to rise.

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11
Q

Does warm air hold moisture?

A

No.

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12
Q

Does cold air hold moisture?

A

Yes, so clouds form when air rises then cools and condenses (at low pressure zones).

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13
Q

At what type of pressure zone are clear skies found?

A

High pressure zones, as cold dense air falls but warms at the same time.

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14
Q

Why do we get wind?

A

When warm air rises, it creates an area of low pressure. Sinking air rushes in from high pressure areas to fill the empty space, and this movement of air is how we get wind.

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15
Q

Where does the vast majority of atmospheric motion occur?

A

The Hadley cell.

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16
Q

Processes at the Hadley cell:

A

The sun warms the Earth at the equator, causing air to rise. This creates a low pressure belt.

As the air rises, it cools and moves towards the poles.

30°N and S of the equator, the cool air sinks, creating a high pressure belt. Little rainfall occurs here so there are deserts in these areas.

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17
Q

What can you do to explain global atmospheric circulation in exams?

A

Draw the diagram!!

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18
Q

What do we mean by saying the ferrel cell is thermally indirect?

A

The motion that occurs is not directly caused by heating from the sun.

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19
Q

Processes at the Ferrel cell:

A

60° N and S of the equator the warmer surface winds (westerlies) meet colder air from the poles.

The warmer air rises, creating low pressure.

This uplift is responsible for the unstable weather conditions known as depressions.

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20
Q

Processes at the Polar cell:

A

At the poles, the cool air sinks, creating high pressure. The high pressure air is then drawn back towards the lower latitudes (nearer the equator).

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21
Q

What happens at the ground surface 30°N and S of the equator?

A

The cool air warms and either moves back to the equator (as trade winds) or moves towards the poles (as westerlies).

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22
Q

Why do winds curve?

A

Due to the Coriolis effect aka. the bending of winds as Earth rotates.

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23
Q

In what direction does the Coriolis effect deflect winds in the northern hemisphere?

A

To the right which is why wind blows anticlockwise in low pressure zones in the northern hemisphere.

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24
Q

In what direction does the Coriolis effect deflect winds in the southern hemisphere?

A

To the left which is why wind blows clockwise in low pressure zones in the southern hemisphere.

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25
Q

What happens at the ground surface 60°N and S of the equator?

A

Some of the air moves back towards the equator, and the rest moves towards the poles.

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26
Q

Why does climate differ at different latitudes?

A

The earth is a sphere. This means that solar insolation is dispersed differently at different latitudes, which is why climate differs. This is known as differential heating.

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27
Q

What is the climate at the equator like and why?

A

At the equator, the sun hits the Earth’s surface at a right angle (it’s directly overhead).

This means that solar insolation is focused over a small area, which means that heating is intense.

Therefore, the climate at the equator is hot.

So, warm moist air rises (low pressure).

This then condenses to form clouds, which means it rains a lot.

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28
Q

Global atmospheric circulation influences…

A

…weather and climate.

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29
Q

What is the climate at 30°N and S of the equator like and why?

A

By the time air reaches these latitudes, it has released most of its moisture as rain.

This dry air means that there are few clouds and little rainfall, which means that deserts are often found here.

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30
Q

What is the climate at 60°N and S of the equator like and why?

A

Warm air rising at these latitudes brings lots of cloud cover and rainfall, often as low pressure systems carried from the Atlantic by westerly winds (westerlies).

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31
Q

What does the movement of air in loops (cells) from the equator and back do?

A

Give us surface winds and create belts of high and low pressure that affect the climate.

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32
Q

Name the surface winds.

A

-Polar Easterlies
-Westerlies
-Trade winds

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33
Q

Polar Easterlies

A

Winds blowing from the high pressure poles towards the low pressure westerlies.

34
Q

Westerlies

A

Winds blowing from the west to the east in the mid latitudes (30° to 60° N and S). Also known as prevailing winds.

35
Q

Trade winds

A

Surface winds that blow from 30° north or 30° south back towards the equator.

36
Q

Which way do trade winds blow in the southern hemisphere?

A

south-east to north-west (until they reach the equator).

37
Q

Give examples of ‘extreme weather events’

A

Flooding
Tropical storms
Prolonged/heavy rainfall
Snow
Drought
Heatwaves
Wildfires

38
Q

Which cells is the UK located between?

A

The polar cell (bringing cool dry air) and the ferrel cell (bringing warm moist air).

39
Q

What is the jet stream? (not on spec)

A

A narrow band of strong winds that generally blow from west to east across the globe. It affects air masses and hence weather patterns.

40
Q

Which way do trade winds blow in the northern hemisphere?

A

north-east to south-west (until they reach the equator).

41
Q

What happens to trade winds at the equator?

A

They are heated and the cycle begins again.

42
Q

What weather hazards does the UK experience?

A

Thunderstorms
Heat waves
Heavy rainfall
Strong winds
Snow and ice
Drought

43
Q

Strong winds (gales) impacts

A

-Damage to properties
-Disrupted transport
-Uprooted trees and debris which can kill/injure people

44
Q

Example of a strong wind UK

A

In 2018, Storm Ali killed two people when 100mph winds blew over several trees.

45
Q

Heavy rainfall impacts

A

-Too much rain can cause flooding, which can damage homes, disrupt transport links, and drown people

-Recovering from flooding can cost millions of pounds

46
Q

Example of heavy rainfall UK

A

Parts of South Wales flooded in 2018 after over 180mm of rain fell in 48hrs during Storm Callum.

47
Q

Snow and ice impacts

A

-Can cause injuries due to slipping
-Can cause deaths due to the cold
-Schools and businesses forced to shut
-Disruption to travel can have economic impacts

48
Q

Snow and ice example UK

A

In March 2019, the ‘Beast from the East’ brought up to 50cm of snow, causing major disruption to traffic and schools.

49
Q

Drought (a lack of precipitations) impacts

A

-Water supplies can run low, causing economic impacts such as crop failures

-Rules to conserve water (like banning hosepipes) have to be introduced.

50
Q

Drought example UK

A

2022 was a drier than average year for the UK with only 62% of the usual summer rainfall. By autumn 2022, groundwater levels were very low.

51
Q

Thunderstorms impacts

A

-Heavy rain, strong winds, and lightning can all occur

-Lightning can cause fires, which can damage property and the environment, and occasionally kill people.

52
Q

Thunderstorm example UK

A

In July 2014, a series of thunderstorms struck southern and central England, with lightning strikes causing power cuts and delaying flights.

53
Q

Heat wave impacts

A

-During long periods of hot weather, pollution builds up in the air, which can cause heat exhaustion or breathing difficulties - killing people.

-Disruption to transport from rails buckling or roads melting can cause economic impacts

-However, the tourism industry may benefit from the better weather

54
Q

Heat wave example UK

A

2022 was one of the hottest summers on record, with temperatures exceeding 40°C in Lincolnshire.

55
Q

Weather is becoming more extreme in the UK. It’s weather is naturally variable, but…

A

extreme events seem to be becoming more common and severe.

56
Q

What two things should we mention when talking about the UK weather becoming more extreme?

A

Temperature
Rainfall

57
Q

UK temperatures (warmth)

A

The UK’s ten warmest years have all occurred since 2002.

This includes the joint hottest summer on record (2018).

58
Q

UK rainfall

A

More rainfall records were broken between 2010 and 2014 than in any decade on record.

59
Q

Our example of a recent extreme weather event in the UK is…

A

…the somerset levels flooding.

60
Q

Extreme weather events in the UK have impacts on what?

A

Human activity.

61
Q

Types of causes for the Somerset levels flooding.

A

Climatic
Topographic (landscape)
Human (farming)

62
Q

When did the Somerset levels flooding occur?

A

December 2013 to February 2014

63
Q

Human causes of the Somerset levels flooding.

A

The rivers hadn’t been dredged regularly for 20 years, which reduced their capacity meaning they’d overflow more quickly.

Due to arable farming, the soil would’ve been compacted. Without air in the soil, it becomes impermeable so more water runs off into drainage basins.

64
Q

Dredging

A

Clearing rivers of sediment.

65
Q

Soil type somerset levels. (topographical cause)

A

The ground is made up of impermeable soil types (clay and peat). This means that water cannot pass easily into the ground, which leads to extensive flooding in periods of heavy rainfall.

66
Q

How did urbanisation influence the somerset levels flooding?

A

Urbanisation leads to the building of new roads and other surfaces using impermeable materials such as concrete.

This means that surface runoff increases which means that flooding increases also.

67
Q

Relief of the land somerset levels (topographical cause).

A

The land is located just 3-4 m above sea level.

This means that the levels are an extensive area of floodplains and marsh, which makes them vulnerable.

68
Q

Economic impact of Somerset levels flooding

A

Costly
Loss of tourism
Agricultural land underwater

69
Q

Cost of Damage Somerset levels flooding

A

£80 million

70
Q

Local companies lost how much in business?

A

Over £1.2 million

71
Q

A Loss of tourism cost the county…(Somerset levels flooding)

A

£200 million

72
Q

How many farms were evacuated and why? (somerset levels flooding)

A

16 farms were evacuated.

Because over 1400 hectares of agricultural land were flooded and so underwater, a huge economic blow for many.

73
Q

Environmental impact of Somerset levels flooding

A

11, 500 hectares of land was flooded, including farmland - this destroyed many crops.

Standing water

Mud and debris left by the flood, damaging vegetation.

74
Q

Standing water (somerset levels flooding)

A

Standing water made the ground toxic and unproductive for over a year.

This meant a loss of nutrients and damage to the structure of the soil, which decreased the long-term fertility of the land.

75
Q

Social impacts of the Somerset levels flooding

A

-villages cut off
-homes damaged
-insurance prices soared so people couldn’t afford to insure their homes against future flooding
-electricity lines damaged
FIX USING TEXTBOOK

76
Q

How many homes flooded somerset levels flooding?

A

more than 600
-this meant that many were forced to evacuate and live in temporary accommodation for months.

77
Q

Villages such as Muchelney were…

A

…cut off by road, so the only way in or out was by boat.

78
Q

Management strategies used to reduce flood risk:

A

Monitoring
Prediction
Protection
Planning

79
Q

Prediction and protection (Somerset Levels flooding)

A

Warning systems were used (e.g. from the Met Office).

This meant that people had time to prepare, for example by finding emergency accommodation in case they had to leave their homes.

Individuals and local authorities used sandbags and flood boards to try and limit flood damage to homes.

80
Q

Somerset Levels and Moors Flood Action plan

A

A 20 year plan set up since the flood which aims to limit the risk of future flooding.

81
Q

For the ‘Somerset Levels and Moors Flood Action plan’, £100 million will be spent on what?

A

-regular dredging of the rivers Parrett and Tone
-turning temporary pumping stations into permanent ones
-building a tidal barrage at Bridgewater
-Widening the River Sowy’s channel and King’s Sedgemoor drain

82
Q

Climatic causes of the Somerset levels flooding.

A

Prolonged and heavy rainfall are arguably the root cause of the floods.

350mm of rainfall in January and February followed the wettest year recorded. This meant it was falling on already saturated ground, which meant increased surface run off.

This coincided with high tides and storm surges swept up the Bristol Chanel, which prevented freshwater from reaching the sea. This meant that the volume of water in rivers increased drastically, which is why they burst their banks.

Geography (19 decks)

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