Global Hazards

• What are the three types of atmospheric circulation cells?


  Hadley, Ferrel, Polar
• What are large scale movements of air called?


  Winds
• What are the types of surface winds?

  Westerlies (blow towards the Poles), Trade winds (blows towards the Equator)
• What are surface winds?

  Cool air that has sunk 30 degrees N and S of the Earth's equator
• Hot air forms...

  Low pressure belts
• Cool air forms...

  High pressure belts
• What happens at the equator?

  • Sun warms the earth via the equator
  • Hot air rises and forms a low pressure belt
  • Air begins to cool and condenses water vapour
  • Rain and clouds
• What happens 30 degrees N and S?

  • Cool air falls, causes high pressure belt
  • Minimal rainfall and no clouds
  • Surface winds blow the air towards/away from equator
• What happens at 60 degrees N and S?

  • Cold air blown from poles meet warm surface winds
  • Low pressure belts (rain and clouds)
  • Air travels to equator and towards poles
• What happens at the Poles?

  • High pressure belts - cool air sinks
  • High pressure goes back towards equator as surface winds
• Where are polar climates found?

  At the poles
• Where are arid (dry) climates found?

  30 degrees N and S - high pressure belt means no rainfall
• Where are temperate climates found?

  60 degrees N and S - low pressure belt means rainfall
• Where are tropical climates found?


  By the equator - low pressure belt means lots of rainfall
• El Niño (3-4 years)


  Trade winds are weak, blow east.

  Warm water in SA, colder water in the deep ocean, fish stay in ocean.

  South America - rain, floods, warm water

  Australia - dry, droughts.
• La Niña (2-7 years)


  Trade winds are strong, blow west

  Pacific water is colder than usual as more is exposed

  More active hurricane season in Atlantic (extreme weather)

  South America - dry, droughts

  Australia - rain and floods
• What conditions do a hurricane need to form?


  Sea must be at least 60m deep

  Temperature must be at least 27C

  Must be 5-30 degrees north/south of the equator

  Wind speed must be at least 75mph