Weather Hazards

Global Atmospheric Circulation

• Worldwide system of winds moving heat from the equator to the poles to reach a balance in temperature

• Air moves due to difference in air pressure (area of high pressure to low pressure) which generates wind

• This pressure difference is because the sun heats the earth surface unevenly

• Insolation that reaches the Earth's surface is greater at the equator than at the poles due to Earth's curvature and angle of the Earth's tilt

3 Cell atmospheric wind model

• The sun warms the earth at the equator causing the air to rise

• This creates a low pressure belt

• As that air rises it cools and moves away from the equator

• 30 north and south of the equator cool air sinks creating a high pressure belt

• At the ground surface the cool air moves either back to the equator (trade winds) or towards poles (westerlies)

• 60 north and south of the equator the warmer surface wind meet colder air from the poles

• The warmer air rises creating low pressure

• Some of the air moves back towards the equator and the rest moves towards the poles

• At the poles cool air sinks creating high pressure

• The high pressure air is then drawback to equator

Where is each cell in atmospheric circulation model located?

• Hadley Cell - Located near the equator (0° to 30°)

• Ferrel Cell - Found in the mid-latitudes (30° to 60°)

• Polar Cell - Situated near the poles (60° to 90°)

• Moves surplus heat

Coriolis Effect

• Each cell has prevailing winds associated with it 

• These winds are influenced by the Coriolis effect

• The Coriolis effect is the appearance that global winds and ocean currents curve as they move

• The curve is due to the Earth's rotation on its axis, and this forces the winds to actually blow diagonally

• The Coriolis effect influences wind direction around the world in this way:

  • In the northern hemisphere, it curves winds to the right

  • In the southern hemisphere, it curves them left

exception is low pressure systems where wind flow in reverse (anticlockwise in northern clockwise is southern)

Global wind belts: surface winds

• The trade winds: Blow from the subtropical high-pressure belts (30 degrees N and S) towards the Equator's low-pressure zones and are deflected by the Coriolis force

• The westerlies: Blow from the sub-tropical high-pressure belts to the mid-latitude low areas but, again, are deflected by the Coriolis force

• The easterlies: Polar easterlies meet the westerlies at 60 degrees S

Name the major global surface winds.

• Trade winds (0°–30°)

• Westerlies (30°–60°)

• Polar easterlies (60°–90°)

How does global circulation influence climate?

• Rainforests are near Equator

• Deserts are at 30°

• UK is wet and mild

• Poles are cold and dry

Why does air rise at 60° latitude?

• Warm air from Ferrel cell meets cold polar air

• Warm air is forced to rise

• Creates low pressure

• Frequent storms

: Why is the UK wetter than 30° regions?

• Located around 50°–60°

• Rising air at Polar Front

• Low pressure systems

• Frequent rainfall

Why are there deserts around 30° latitude?

• Air rises at Equator

• Moves poleward

• Cools and sinks at 30°

• Sinking air = high pressure

• Little cloud formation

• Dry conditions

What is a tropical storm?

A large, rotating low-pressure system that forms over warm tropical oceans, bringing very strong winds, heavy rainfall, storm surges, and sometimes tornadoes.

Why are they called hurricanes / typhoons / cyclones?

A: Same hazard, different regions:

• Hurricanes = Atlantic + NE Pacific

• Typhoons = NW Pacific (East Asia)

• Cyclones = Indian Ocean + SW Pacific (e.g., Australia)

Where do tropical storms form globally (latitudes)?

• Over warm tropical oceans

• Between 5° and 30° north and south of the equator

• When winds converge (meet) near the ocean surface

• There is low vertical wind shear

Three main structural components of a tropical storm

• The eye - Central zone up to 50 km wide with very low pressure, light winds, clear skies, no rain, and high temperatures

• The eyewall - Surrounds the eye with spiralling air, extremely strong winds (around 160 km/hour), dense clouds, and torrential rain → most destructive

• Outer edges - Beyond the eyewall with decreasing wind speeds, scattered clouds, less rainfall, and rising temperatures

How do tropical storms form?

• warm surface water evaporates rises and condenses into clouds

• This releases huge amount of energy producing powerful storms

• The rising air creates an area of low pressure which increases surface winds

• Low wind shear prevent clouds breaking up as they rise so storm stays intact

• Easterly wind near the equator move tropical storms toward the west

• Storms spin due to coriolis effect

• as storm moves over ocean the energy from the warm water strengthens the storm so wind speeds increase

• storms lose strength when the move to land or cooler water because their energy supply from the warm water is cut off

How might climate change affect distribution/frequency/intensity of tropical storms?

• Global temperatures are set to rise as a result of global warming

• More of the world's oceans will be above 27° C, therefore, more places across the world will experience tropical storms

• Oceans will stay at 27°C or higher for longer during the year, which will increase the annual number of tropical storms 

• Higher temperatures will mean storms will be stronger and more frequent and cause more damage

What are Primary effects and secondary effect

• Primary effects are the immediate impacts of strong winds, high rainfall and storm surges

• Secondary effects are the impacts that occur later on, after the storm has passed

Primary impacts of tropical storms

• Buildings and bridges are destroyed

• Roads, railways, ports, and airports are damaged

• Electricity lines are damaged/destroyed

• Gas lines broken

• Sewage overflows

• Rivers and coastal areas are flooded

• Businesses destroyed

Secondary impacts of tropical storms

• lack of shelter leaves people homeless - distress/poverty/ill helath/death

• cost of rebuilding can be expensive and some people may not have insurance

• Blocked or destroyed roads prevent rescue and emergency vehicles and aid from getting through

• Life support systems, hospitals, shops and homes left without power supplies

• Clean water supplies are contaimnated - increase of waterborne diseases and death

• Crops livestock and habitats are destroyed leading to shortage of food and famine

What are immediate responses?

Immediate response

• When a tropical storm is forecasted (predicted) to hit an area

• As the tropical storm is happening

• Immediately after the tropical storm has passed

What are long term responses?

• Long-term responses are:

  • Restoring an area to its past conditions

  • Reducing the impact of future storms 

Immediate responses to tropical storms

• Evacuation of people before the tropical storm arrives

• Rescue people before the storm cuts people off from flooding and treat injured people

• Temporary shelters for the homless and post notices where they are being housed for missing family members

• Provide temporary supplies for power/food and water and restore communication systems

• Overseas aid may be sent in the form of workers, supplies, equipment or financial donations

Long term responses to tropical storms

• Improve long-term forecasting techniques to give people more time to evacuate in the future

• Repair and improve flood defences – floodgates, levees, etc. 

• Provide aid, grants or subsidies to residents to repair and strengthen their properties

• Repair, replace and improve infrastructure

• Improve building regulations so that more buildings withstand the impacts of tropical storms or change planning rules to restrict homes being built in risk areas

How does monitoring and prediction reduce effect of tropical storms?

• storms can be monitored using radar satellites and aircraft

• computer models can then be used to calculate storms predicted path

• predicted where and when tropical storm is going to happen gives people time to evacuate and protects homes and businesses

• eg. Typhoon Haiyan predicted storm path and helped authroties dcide which areas need to be evacuated

How does planning reduce effect of tropical storms?

• future devleopment eg. enw house can avoid high risk areas such as low lying costal zones

• government can plan evacuation routes to ensure people can get away quickly

• emergency services can prepare for disasters by practising rescuing people from flooded areas

• eg. Typhoon Haiyan volunteer started resuce simulation to prepare for future storms

How does protection reduce effect of tropical storms?

• building can be designed to withstand tropical storms

• buidling can also be put on stilts so they are safe from flood water

• flood defences can be built along rivers (levees and sea walls)

• eg. mangrove forests are being planted in Philippines to act as natural flood defence

Five types of air masses that bring different weather to the UK

Air Mass	Weather
Polar Maritime	Cold and wet
Arctic Maritime	Very cold and wet
Polar Continental	Cold and dry
Tropical Continental	Warm and dry
Tropical Maritime	Warm and wet

Extreme weather in the UK (all)

• Depressions

  • very wet unstable low pressure weather

  • form when warm air meet cold air and strongest wind and heaviest rain are in autmn as summer heat meets polar air

• Anticyclones

  • very cold or very hot stable high pressure dry weather

  • winter anticyclones bring longer periods of cold foggy weather

UK weather hazards

• strong winds

• heavy rainfall

• heatwaves

• thunderstorms

• drought

• snow and ice

Weather Hazard - Strong Winds

• Strong gales (winds) damage properties and cause general disruptions

• Uprooted trees and debris can injure or kill

• Winds are strongest in coastal areas, particularly the west coast and upland areas

• eg. Storm Ali 2018 - 100mph winds blew over several trees

Weather Hazard - Heavy Rainfall

• Flooding causes damage to homes and possessions, disrupts transport networks

• Costs for recovery can cost millions of pounds

• eg. South Wales flooded in 2018 after over 180mm of rain feel in 48 hours during Storm Callum

Weather Hazard - Snow and Ice

• Causes injury through slips and falls

• Death through the cold

• Closures have an economic impact on businesses, transportation, and schools

• eg. Beast from the East brough up to 50cm of snow causing major disruption to traffic and schools

Weather Hazard - Drought

• Water supplies run low

• Causes economic impacts through loss of crops, death of animals, loss of wildlife

• Water supply restrictions and hosepipe bans impact people

• eg. 2022 drier that the average year for UK 62% of the usual summer rainfall ground water levels were also very low

Weather Hazard - Thunderstorms

• Heavy rain, lightning and strong winds

• Most common in summer in the south and east of the UK

• Lightning strikes can kill and can also cause fires and damage properties and the environment

• july 2014 - series of thunderstorms struck south and central england with lightning strikes causing power cuts/delaying flights

Weather Hazard - Heatwaves

• Long periods of extremely hot weather cause breathing difficulties, death and heat exhaustion

• Roads can melt and rails buckle under the heat, which disrupts transport

• Tourism may benefit from good weather

• eg. 2022 was one of the hottest summer on record with temperature exceeding 40C Lincolnshire

Prediction that weather in UK is becoming more extreme

• IPCC has warned temp will increase during this century

• Global warming increases the frequency and intensity of extreme weather events through increased evaporation and rainfall

• Scientists believe UK will continue to experience higher amount of rainfall and increased temperatures (1980s extreme winter rainfall has increased)

• Uk temp has increased about 1C since 1980

Evidence that weather in UK is becoming more extreme

• UK ten warmest years have occurred since 2002

• 2018 was joint hottest summer on record

• Extreme colt event are more frequent with seven of the UKs eleven coldest recorded temperature since 1980 and December 2010 was the coldest month for over a 100 years

• More rainfall record were broken between 2010-2014 than in any decade on record

• Major flooding events have become more frequent over the past 10 years

• December 2015 was the wettest month ever recorded and sever flooding occurred in many areas of the UK

Evidence of climate change - earth is getting warmer

• Quaternary period span from about 2.6 million year ago to present day

• Last ice age ended approximately 12000 years ago

• Global temperature has shifted between cold glacial periods that last about 100000 years to warmer interglacial periods that last around 10000 years

• The last glacial period was 15k years ago since then earth has been warming

• Global warming is the term used to describe sharp rise in global temperatures over the last century

Evidence of climate change - Ice and Sediment Cores

• Ice sheets are made up of layers of ice one layer is formed each year

• Drill into ice sheets to get long cores of ice

• Analyse gases trapped in layer of ice we can predict temperature each year

• Remains of organisms found in cores taken from ocean sediments can also be analysed

• These extend temperature record back at least 5 million years

Evidence of climate change - Pollen Analysis

• Pollen from plants get preserved in sediment

• Scientists can identify and data preserved pollen to show which species were living at that time

• Scientists know the conditions that plants live in now so preserved pollen from similar plants shows that climate conditions were similar

Evidence of climate change - Tree rings

• Tree ring grows - new ring each year the tree ring are thick in warm wet conditions

• Scientists take cores and count the rings to find the age of the tree

• The thickness of each ring shows what climate is like

• Reliable source of evidence of climate change for past 10k years

Climate change causes

• greenhouse effect

• allow short wave radiation to pass through and reach earth surface

• earth surface absorbs this and releases it as long wave radiation

• ghgs then abosrb this and re radiate it in all directions

• maintain earth temp/increasing earth temperature

Greenhouse gases from natural sources

• Water vapour: Evaporation from the oceans/seas and plants

• Carbon dioxide: Volcanic eruptions, wildfires and respiration

• Methane: Emitted from oceans and soils as part of decomposition, termites also emit methane

• Nitrous oxide: Soils and oceans

Causes of natural climate change

• Milankovitch Cycles (Orbital changes)

• Volcanity activity

• Solar output

• Atmospheric dust

Causes of natural climate change - Orbital Changes

• Affect how much solar radiation the earth receives

• More energy = more warming

• Variations in the way earth orbits around the sun

  • Strech - earth orbit around sun varies from circular (cooler) and ellipitcal warmer) change happens ever 100000 years - eccentricity

  • Tilt - Axis tilted at an angle (40k years) greater the tilt the hotter the summer the cooler the winters

  • Wobble - every 24k years earth wobbles on its axis (precession) this affect seasonal temp

• Could have caused the glacial and interglacial cycles of the Quaternary period

Causes of natural climate change - Volcanic Activity

• Large scale eruptions lead to vast quantities of ash being ejected into the atmosphere

• Ash in the atmosphere blocks solar radiation leading to a decrease in temperatures

Solar Output

• Suns energy output isnt constant and changes in short cycles (11 years)

• Reduced solar output means that the Earth climate may become cooler in some areas

• Solar output isn’t thought to have major effect on global climate change

Causes of natural climate change - Human Activity Examples

• GHGs

• Fossil Fuels

• Agriculture

• Construction

• Deforestation

Causes of natural climate change - Fossil Fuels

• Fossil fuels account for almost 50% of global greenhouse gas emissions

• Fossil fuels are used in transportation, construction, heating, manufacturing and energy production 

Causes of natural climate change - Agriculture

• Farming livestock produces lots of methane

• Rice paddies contribute to global warming because flooded fields emit methane

• Deforestation to clear land for grazing reduced plant to do photosynthesis

• When trees are cut down they stop taking CO2

• CO2 is also released into the atmosphere when trees are burnt as fuel

• The production of fertilisers and pesticides uses fossil fuels

Causes of natural climate change - Construction + Transport

•  The manufacture of cement releases CO₂ - it is made from limestone which contains carbon

• The increasing global population has led to increased numbers of cars, lorries and planes

• Most transport uses petrol/diesel which comes from oil as fuel this releases CO₂

Effect of climate change - Social effects

• Health

• Increased temp and lack of precipitation lead to spread of diseases

• eg. Italy since 2017 when it was previously malaria free

• Heatwaves more common

  • Heat stroke/dehydration/sunburn

  • Respiratory diseases affected

• Loss of Jobs due to changes in tourism and agriculture

• Homes - Increased flooding due to sea level rise and increase frequency/severity of storms will lead to displacement of large numbers of people

Effect of climate change - Economic Effects

• Agriculture

  • Farmers may need to change the crop they grow if climate conditions become unsuitable

  • Reduced water availability mean irrigation is limited

  • Food shortages will lead to malnutrition and famine

• Employment

  • Job opportunites may change or decrease

  • Tourism may decline in some areas (ski resorts have less reliable snow)

  • Farmer may have to change crop they grow or leave farming

  • Agirculture/Fishing may decline due to rising temp and rainfall patterns

• Settlements

  • In low lying Ares may have to be abandoned or need additional defences against sea level rise (costly)

Effect of climate change - Environmental Effects

• Sea level rise

  • Warmer temp cause the water in sea to expand increasing sea level

• Melting ice

  • Average sea level has risen from 23cm to 1880

  • Sea levels are forecast 30cm by 2050

• Low lying costal areas are in high risk of flooding (eg. Maldives)

• Beach erosion will increase so greater coastal erosion

Mitigation strategies to reduce climate change

• Planting trees

• Carbon Capture

• Alternative Energy Production

• International Agreements

Mitigation Climate Change - Planting trees

• Planting trees increases the removal of CO₂ from the atmosphere

• Oxygen is created during photosynthesis

• Increased transpiration increases cloud formation which reduces incoming solar radiation

Mitigation Climate Change - Alternative Energy Production

• Replacing fossil fuels with nuclear/renewable energy resources to reduce GHGs emissions eg. Offshore wind farms/tidal project/nuclear pp

• They are becoming cheaper

• Renewable energy is not as efficient as fossil fuels

Mitigation Climate Change - Carbon Capture CCS

• Captures and removes CO₂ before it is emitted: 

  • The CO₂ is then compressed and stored underground

  • This is an expensive process and is not economically viable yet

  • It is unknown whether the CO₂ will be able to be stored long term 

Mitigation Climate Change - International Agreements

• Paris Agreement 2015 - reduce ghg emission and limit global warming

• Global agreement to limit global warming to 2C (preferable 1.5C) above pre industrial levels

• Argument also includes reducing CO2 emission by at least 60% by year 2050

• Signed by 196 countries

• encourages developed countries to help developing countries put mitigation strategies in place

• each country has submitted a pledge which indicates how much they will try reduce GHGs emission by (UK said at least 68% by 2030 from 1990)

Adaptation Climate Change

• Responding to effects of climate change

• Changing Agricultural systems

• Managing water supply

• Coping with rising sea levels

Adaptation Climate Change - Changing Agricultural systems

• Changing rainfall patterns and higher temp will affect productivity of existing systems

• It may be necessary to plant new crop types that are more suited to climatic conditions

• Development of drought-resistant crops (Millet In Kenya for example)

Adaptation Climate Change - Managing Water Supplies

• Reducing demand through the use of water-efficient appliances and devices (shower heads, dual flush toilets)

• Increasing supply through desalinisation

• Water storage facilities 

• Improved irrigation systems which waste/use less water

Adaptation Climate Change - Coping with rising sea levels

• Construction of sea walls as in the Maldives

• Mangrove forest restoration which protects the land from coastal flooding

• Raised homes on stilts and embankments in LICs

• Construction of artificial islands up to 3m high

• Flood barriers such as the Thames Barrier 

• Predicted to rise between 0.28m - 1.01m by 2100

Hadley Cell

• Largest cell

• Extends from the equator 30 and 40 north and south

• Air flows towards higher latitudes where it becomes cooler and sinks over subtropical regions

• Dry cloudless → warmed by sun as it descends climate is warm and dry

Mechanisms of why we get variations of temperatures

• Volcanic eruptions can dim global for about a year (eject ash into the sku → jet sream can circulate around the world → global dimming)

• Solar flares can affect global temperatures for years and sometimes pules (sunspots)

  • Incoming solar radiation (insolation)

Ferrel Cell

• Middle cell

• Occurs from edge of Hadley cell 60-70 degrees north and south of the equator

Tropical Storm Features

• ITCZ - south of tropic of cancer and north of tropic of capricorn

  • between 5 degrees and 30 degrees north and south of the equator

• High Insolation (direct sunlight) → High temperatures

• Temp above 27C

• Sea depth = 60-70m

• Require heat and moisture from warm air to rise

• Low pressure

• Latent Heat is released which power tropical storm

• Low “Shear” Wind →

• “Season” is between 1st June and 30 Nov

Tropical Rain forest

How do tropical storms develop?

• Tropical storms form between approximately 5° and 30° latitude. Because of easterly winds they initially move westward.

• The air above the warm ocean is heated. Once the ocean water reaches at least 27°C, the warm air rises quickly, causing an area of very low pressure.

• As the air continues to rise quickly it draws more warm moist air up from above the ocean leading to strong winds.

• The rapidly rising warm air spirals upwards, cools, condenses and large cumulonimbus clouds form.

• These clouds form the eye wall of the storm and produce heavy rainfall.

• In the centre of the storm, cold air sinks forming the eye of the storm - here, conditions are calm and dry.

Mitigation

Reducing greenhouse gas emissions, therefore reducing future warming 

Adaptation

Changing the way we live so we can thrive/survive in the changing global climate. 

Mitigation vs Adaptation Examples