weather hazards ⛈️

• global atmospheric circulation: transfer of heat from the equator to the poles by movement of air
• air moves due to difference in air pressure (air moves from high pressure areas to low pressure areas)
• the global atmospheric circulation system is divided into cells
• each cell has:

  • warm rising air that creates a low pressure belt
  • cool sinking air that creates a high pressure belt
• each hemisphere has 3 cells
• the 3 cell types are hadley cell, ferrel cell and polar cell
• hadley cells:

  1. the sun warms the earth at the equator, causing the air to rise and creating a low pressure belt
  2. as the air rises it cools and moves away from the equator
  3. at 30° north or south of the equator, the cool air sinks and creates a high pressure belt
• coriolis effect: the curving of winds due to the earth‘s rotation
• ferrel cells: at the ground surface, the cool air moves either…

  • back towards the equator as trade winds
  • or towards the poles as westerlies
• polar cells:

  1. at 60° north or south of the equator the warmer surface winds meet colder air from the poles
  2. the warmer air rises and creates low pressure
  3. some of the air moves back towards the equator and the rest moves towards the poles
  4. at the poles the cool air sinks and creates high pressure
  5. the high pressure air is drawn back towards the equator
• at the equator:

  • sun is directly overhead, meaning the earth’s surface receives a lot of of solar radiation, so it’s hot
  • warm moist air rises and forms clouds so it rains a lot
• at 30° north and south of the equator:

  • the air has released most of its moisture as rain
  • the dry air means there are few clouds and little rainfall
  • deserts are often found at this latitude
• uk climate:

  • the uk lies in the low pressure zone 60° north of the equator
  • warm rising air brings lots of cloud cover and rainfall
  • low pressure systems are carried from the atlantic by westerly winds