global hazards

• Global pattern of air circulation


  Atmospheric circulation is the large-scale movement of air by which heat is distributed on the surface of the Earth
• Cells of atmospheric circulation

  • Hadley cell
  • Ferrel cell
  • Polar cell
• Hadley cell


  • Largest cell which extends from the Equator to between 30° to 40° north & south
• Ferrel cell


  • Middle cell where air flows poleward between 60° & 70° latitude
• Polar cell


  • Smallest & weakness cell that occurs from the poles to the Ferrel cell
• Pressure

  • High Pressure
  • Low Pressure
• High Pressure


  Caused by cold air sinking. Causes clear and calm weather
• Low Pressure


  Caused by hot air rising. Causes stormy, cloudy weather
• Climate Zones

  • Temperate Climate
  • Tropical Climate
  • Polar Climate
  • Desert Climate
• Temperate Climate


  Mid-latitude, 50° - 60° north &south of the Equator. Here air rises and cools to form clouds and therefore frequent rainfall. e.g. UK
• Tropical Climate


  Found along the Equatorial belt, this zones experiences heavy rainfall and thunderstorms. E.g. Brazil
• Desert Climate


  30° north and south of the equator, sinking dry airs leads to high temperatures without conditions for rainfall. E.g. Libya
• Wind


  The movement of air from an area of high pressure to one of low pressure
• Types of wind


  • Katabatic Winds
  • Trade Winds
  • Jet Streams
• Katabatic Winds


  Winds that carry air from the high ground down a slope due to gravity. e.g. Antarctic
• Trade Winds


  Wind that blow from high pressure belts to low pressure belts
• Jet Streams


  These are winds that are high in the atmosphere travelling at speeds of 225km/h
• Precipitation

  This is when water vapour is carried by warm air that rises. As it gets higher, the air cools and the water vapour condenses to form a cloud. As water molecule collide and become heavier, the water will fall to Earth as precipitation
• Types of precipitation

  • Convectional Rainfall
  • Frontal Rainfall
  • Relief Rainfall
• Convectional Rainfall

  When the land warms up, it heats the air enough to expand and rise. As the air rises it cools and condenses. If this process continues then rain will fall
• Frontal Rainfall

  When warm air meets cool air an front is formed. As the warm air rises over the cool air, clouds are produced. Eventually steady rain is produced
• Relief Rainfall

  When wind meets mountains, the warm air is forced to rise quickly and cool. This leads condensation and eventually rainfall. When the air descend however, very little rainfall falls, creating a rain shadow
• Extremes in weather conditions

  • Wellington, New Zealand
  • Puerto Lopez
  • The Atacama, Chile
  • Mawsynram, India
• Wellington, New Zealand

  Very high wind speeds (248mkm/h) due to the surrounding mountains funnelling wind
• Puerto Lopez

  Found along the equator, high temperatures lead to rapid condensation and heavy rainfall
• The Atacama, Chile

  The Andes mountains block moist warm travelling any further west. This causes rainfall to the east, but a rain shallow to the west
• Mawsynram, India

  This village see a lot of rain each year (11m per yr). This is due to the reversal of air conditions/directions from sea to land. In the summer, this contributes to monsoons
• Tropical Storms occur between the tropics of Cancer and Capricorn
• Formation of Tropical Storms

  1. The sun's rays heats large areas of ocean in the summer

  2. Once the temperature is +26.5⁰C, the rising warm moist air leads to a low pressure. This turns into a thunderstorm, causing air to be sucked in

  3. With trade winds blowing in the opposite direction and the rotation of earth involved (Coriolis effect), the thunderstorm will start to spin

  4. When the storm begins to spin faster than 74mph it is a tropical storm

  5. With the tropical storm growing in power, more cool air sinks in the centre of the storm, creating calm, clear condition called the eye

  6. When the tropical storm hit land, it loses its energy source (the warm ocean) and it begins to lose strength. Eventually it will 'blow itself out'
• Causes of Drought

  • El Nino effect
• El Nino effect

  Normally, warm ocean currents off the coast of Australia cause moist warm air to rise and condense causing storms and rain over Australia. In an El Niño year (every 2-7 years) the cycle reverses. Cooler water off the coast of Australia reverses the wind direction leading to dry, sinking air over Australia causing hot weather and a lack of rainfall
• Drought can occur anywhere throughout the world but they are more frequent between the tropics of Cancer and Capricorn. Many countries in Africa suffer from severe drought, such as Ethiopia but Australia also suffer
• Tropical Storms

  Scientist believe that global warming is having an impact on the frequency and strength of tropical storms. This may be due to an increase in ocean temperatures
• Droughts

  The severity of droughts have increase since the 1940s. This may be due to changing rainfall and evaporation patterns related to gradual climate change
• Causes of 40.3oC temperatures in the UK

  • High pressure (air sinking) called Azores high came north from Spain
  • Heat built up due to the strong high summer sun and long summer days
  • A heat dome trapped the hot air causing record temperatures
  • Global warming is increasing UK heatwave temperatures
• Effects

  • 10th – 25th July excess deaths = 2,227
  • 41 properties damaged by fire in London
  • Heat related illness (especially elderly) caused a spike in 999 calls and pressure on the NHS
  • 33 hectares of Norfolk's Ken Reserve destroyed by wild fire
• Management

  • The Met Office issued a red warning of risk to life. People told to stay in and avoid travel
  • Railway speeds reduced to prevent tracks buckling and avoid rail accidents
  • Norfolk Council advised against BBQs and leaving glass bottles
• Causes (also see formation of tropical storms above)

  1. Started as a tropical depression in the Pacific Ocean 7oN of the equator. The sea temperature was 28oC and depth over 60 metres

  2. It built up energy over the ocean and became a Category 5 "super typhoon" with winds 195mph and a 20 foot storm surge

  3. The Philippines is an EDC and is ranked 117 out of 187 for development
• Effects

  • 6300 deaths = families devastated
  • 130,000 homes destroyed
  • 130,000 tonnes of rice destroyed
  • $85 million of farm damage
  • Water and sewerage systems destroyed caused diseases
• Management

  • The UN raised £190m in aid for emergency food, water, shelter and medical support
  • Emergency aid included – food for 4 million people, emergency shelters for 500,000 people
  • Long-term aid = Cash for work schemes paid local people to clean debris and repair infrastructure e.g. roads