Content

• Atmospheric circulation is the large-scale movement of air by which heat is distributed on the surface of the Earth.
• Hadley Cell - largest cell which extends from the Equator to between 30* to 40* north & south
• Ferrel Cell - middle cell where air flows polewards between 60* & 70* latitude
• Polar Cell - smallest & weakness cell that occurs from the poles to the Ferrel Cell
• Droughts

  • Can occur anywhere throughout the world
  • More frequent between the tropics of Cancer and Capricorn
  • Many countries in Africa suffer from severe drought e.g. Ethiopia
  • Australia also suffer
• The global circulation system controls temperatures by influencing precipitation and the prevailing winds. This creates distinctive climate zones.
• 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
• Polar Climate - within the polar zones cold air sinks causing dry, icy and strong winds e.g. Antarctica
• Desert Climate - 30* north & south of the equator, sinking dry airs leads to high temperatures without conditions for rainfall e.g. Libya
• High pressure - cause by cold air sinking. causes clear and calm weather
• Low pressure - caused by hot air rising. causes stormy, cloudy weather
• Wind is the movement of air from an area of high pressure to one of low pressure.
• Causes of drought: El Niño effect

  • Also associated with creating dry conditions
  • 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
• Distribution of Tropical Storms:

  • Known by many names including hurricanes (North America), cyclones (India) and typhoons (Japan and East Asia).
  • All occur in a band that lies roughly between the tropics of Cancer and Capricorn and despite varying wind speeds are ferocious storms.
  • Some storms can form just outside of the tropics, but generally the distribution of these storms is controlled by the places where sea temperatures rise above 27*C
• What causes warm, moist air to rise over large areas of the ocean in summer and autumn?

  The sun's heat
• At what temperature does rising warm moist air lead to low pressure?


  27°C
• What phenomenon occurs when warm moist air rises and leads to low pressure?


  A thunderstorm
• What role do trade winds play in the formation of tropical storms?


  They suck in air towards the low pressure area
• How does the Coriolis effect influence the formation of tropical storms?


  It causes the thunderstorm to start spinning
• What wind speed indicates that a tropical storm is officially born?


  74 mph
• What is the calm, clear condition at the center of a tropical storm called?

  The eye of the storm
• What happens to a tropical storm when it hits land?


  It loses its energy source and begins to lose strength
• What is the ultimate fate of a tropical storm after it loses strength?


  It will 'blow itself out'
• Katabatic Winds


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


  Wind that blows 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.
• What is precipitation?


  When air 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.
• Wellington, New Nealand 


  Very high wind speeds (248km/h) due to the surrounding mountains funelling wind.
• 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.
• Puerto Lopez


  Found along the equator, high temperatures lead to rapid condensation and heavy rainfall.
• Mawsynram, India


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


  Scientists 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 drought have increased since the 1940s. This may be due to changing rainfall and evaporation patterns related to gradual climate change.
• The Crust


  Varies in thickness (5-10km) beneath the ocean. Made up of several large plates.
• The Mantle


  Widest layer (2900km thick). The heat and pressure means the rock is in a liquid state that is in a state of convection.
• The Inner and Outer Core


  Hottest section (5000 degrees). Mostly made of iron and nickel and is 4x denser than the crust. Inner section is solid whereas outer layer is layer.