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• Global Atmospheric Circulation is the transfer of heat from the equator to the poles through the movement of air.
• Air moves as a result of differences in air pressure - winds blow from high pressure areas to low pressure areas.
• The Atmospheric Circulation is split into 3 cells:

  • Hadley Cell (0-30 degrees north/south)
  • Ferrel Cell (30-60 degrees north/south)
  • Polar Cell (60-90 degrees north/south)

  Each hemisphere has 3 cells, each cell has warm rising air which creates a low pressure belt and cool sinking air which creates a high pressure belt
• Movement of air (hadley --> ferrel)

  • Sun warms the Earth at the equator, causing the air to rise which forms a low pressure belt
  • As the air rises it cools and moves away from the direction (north/south)
  • At the surface, cool air moves either back towards the equator (tradewinds) or towards the poles (westerlies)
  • These winds curve because of the rotation of the Earth - referred to as the coriolis effect
• Movement of air (ferrel --> polar)

  • The surface winds that have moved towards the poles (westerlies) will meet the cooler air from the poles, this causes the warm air to rise at 60 degrees north or south (creates a low pressure belt)
  • Some of this air will move back towards the equator, while the rest moves into the polar cell and heads for the poles
• Movement of air (polar cell)

  • At the poles the air will then sink, this creates high pressure
  • High pressure air is then drawn back towards the equator
• The air which moves in cells from the equator to the poles and back, gives us surface winds and creates pressure belts of high and low pressure which affect the climate.
• At the equator, the sun is directly overhead, meaning the Earth's surface receives a lot of solar radiation, so this causes the equator to be hot. It also rains a lot as a result or warm, moist air rising and forming clouds.
• At 30 degrees north/south of the equator, it will have released most of its moisture as rain, this dry air means there are fewer clouds and very little rainfall, so at these points you will often find deserts.
• The UK lies close to the low pressure zone at 60 degrees north. Warm rising air brings a lot of cloud cover and rainfall at these latitudes, often as low pressure systems carried from the Atlantic by westerly winds.
• Things needed for a tropical storm to develop:

  • Latitude between 5-30 degrees
  • Ocean temperature of 27*C or above
  • Water depth of 60m or more
  • Wind shear between higher and lower parts of the atmosphere low
• Formation of a tropical storm:

  • Warm surface water evaporates, rises, then condenses into clouds
  • This releases huge amounts of energy which produces powerful storms
  • Rising air creates an area of low pressure, increasing the surface winds
  • Low wind shear prevents clouds from breaking up as they rise
• Movement of a tropical storm:

  • Easterly winds from equator move tropical storms towards the west
  • Storms spin as a result of the coriolis effect
  • As the storm moves over the ocean, warm water strengthens storm so wind speed increases
  • Storms lose energy and strength as they travel over land because energy supply is cut off
• Tropical Storms in the Northern Hemisphere typically occur between the months of August-October

  Tropical Storms in the Southern Hemisphere typically occur between the months of December-April
• Tropical storms are circular in shape, and can be up to hundreds of kilometres wide. They normally last between 7-14 days.

  They spin anticlockwise in the Northern Hemisphere and Clockwise in the Southern Hemisphere
• In the Atlantic and North-East Pacific, Tropical storms are referred to as 'Hurricanes'

  In the North-West Pacific, Tropical Storms are referred to as 'Typhoons'

  In most other places (commonly the South Pacific) Tropical Storms are referred to as 'Cyclones'
• The centre of a tropical storm is called the 'Eye' it has very low pressure as well as light winds, no clouds, and a high temperature.
• The 'Eyewall' is the clouds surrounding the Eye of the storm, there is spiralling rising air, as well as very strong winds (around 160km/h), storm (cumulonimbus) clouds, torrential rain and low temperature.
• The edges of the storm is where wind speed begins to fall again, and clouds begin to get smaller and more scattered, rain becomes less intense and temperature increases.
• Climate change will have an effect on these factors of a tropical storm:

  • Frequency (how often it happens)
  • Intensity (how strong it is)
  • Distribution (where it happens)
• Climate change will affect the frequency of tropical storms due to increased ocean temperatures, meaning that the times of year that they form will last longer.
• Climate change will affect the intensity of tropical storms due to increased ocean temperatures allowing more evaporation, which in turn leads to greater cloud formation meaning more energy is released.
• Climate change will affect the distribution of tropical storms due to increased ocean temperatures in much larger areas of the world, allowing tropical storms to form in areas which in the past wouldn't have experienced them before.
• Prediction and Monitoring of tropical storms:

  • With the use of radar, satellites and aircraft. Computer models can then calculate a storms predicted path
  • Predicting where and when a tropical storm will happen gives people time to evacuate and protect people's homes and businesses
• Planning for tropical storms:

  • Future developments can avoid high risk areas
  • Governments set out planned evacuation routes
  • Emergency services can prepare for disasters
• Protection from tropical storms:

  • Buildings designed to withstand tropical storms
  • Flood defences built along rivers
• Types of UK weather hazards include:

  • Strong winds [e.g. Storm Ali]
  • Heavy Rainfall [e.g. Storm Callum]
  • Snow and Ice [e.g. Beast From The East]
  • Drought [2022 UK Heatwave]
  • Thunderstorms [July 2014 Thunderstorms]
  • Heat Waves [2022 UK Heatwave]
• Strong Winds:

  • Strong winds can damage properties and disrupt transport
  • Uprooted trees and debris can injure and kill people
  • E.g. Storm Ali killed 2 people when 100mph winds blew over several trees
• Heavy Rainfall:

  • Too much rain can cause flooding, which damages homes, disrupts transport networks and drowns people
  • Recovering from flooding can cost millions
  • E.g. Parts of South Wales flooded after over 180mm of rain fell in 48 hours during storm Callum
• Snow and Ice:

  • Snow and ice can cause injuries and even death due to cold temperatures and slipping
  • Schools and businesses can be forced to shut and disruption to travel has economic impacts
  • E.g. Beast of the East in March of 2018, brought up to 50cm of snow and caused major traffic and school disruption
• Drought:

  • Low running water supply can cause economic impacts such as crop failures
  • Rules to conserve water like hosepipe bans can be introduced.
  • E.g. 2022 was a very dry year due to 62% of usual summer rainfall, groundwater levels were very low in autumn 2022
• Thunderstorms:

  • Heavy rain and strong winds and lightning all occur during thunderstorms
  • Lightning can cause fires which can damage property and the environment, and can occasionally kill people
  • E.g. A series of thunderstorms struck southern and central England in July 2014 which caused power cuts and delayed flights
• Heatwaves:

  • Long periods of hot weather causes pollution to build up in the air which can cause heat exhaustion or breathing difficulties which can kill
  • Disruption to transport due to rails buckling or roads melting leads to economic impacts
  • E.g. 2022 was one of the hottest summers on record, with temperature even exceeding 40*C (Lincolnshire) for the first time ever in the UK's recorded history
• The UK's weather is naturally becoming more extreme, such as:

  • 10 warmest years have all occurred since 2002
  • 11 coldest recorded temperatures have all occurred since 1980
  • December 2010 was the coldest month in over 100 years
  • 2018 was the hottest summer on record
  • December 2015 was the wettest month ever recorded
  • Major flooding events have become more frequent in the past 10 years
  • More rainfall records broken in 2010-2014 than any decade on record