global hazards

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  • PAPER ONE GEOGRAPHY! Global hazards
    • GLOBAL HAZARDS
      • Winds move from high to low pressure
        • atmospheric circulation
        • the equator: air rises as  its heated via the sun= low pressure belt = clouds+rain
            • at 30 degrees N and S cool air sinks =high pressure belt= cloudless skies =low rainfall
              • surface winds blowing towards the equator is called trade winds, when trade winds meet at the eqator  they rise= clouds
                • 60 degrees N and S  warmer winds meet colder air and warmer air is less dense so rises= low pressures
      • Polar; low temps all year
        • Temperate; moderate summers a low pressure belt rainfall frequent
          • Tropical; hot temps high rainfall near equator ( two cells meeting)
            • Arid; low rainfall hot temps high pressure prevents rainfall
      • Tropical Storms
        • sea temps over 27 degrees
          • warm air rises =condensation= release of energy= powerful storm rising air causes low pressure and more surface winds
            • earths rotaion deflects the path of winds making storms spin
              • extreme winds ; caused by low pressure at the centre  makimg a presssure difference
                • Extreme rain; caused by large amounts of moist air rising, coolimg and condensing
                  • El Nino
                    • the reverse of nromal conditions of the pacific ocean
                    • pressure rises in the west and falls in the east causes trade winds to weaken or reverse
                      • sinking air in high pressure over the west causes dry weather causing drought in australia
                        • rising air in low pressure in the east leads to wet conditions causing floods in peru
                    • La Nina
                      • More extreme conditions of the normal pacific ocean
                        • Trade winds blow stringer, more cold water rises in the east
                          • heavy rainfall and floods in the west and less rainfall/droughts in the east
    • Droughts
      • a long period of time when rainfall is below average
        • Changes in atmospheric circulation i.e el nino can be a cause as it can decrease annual rainfall. also caused by high pressure systems
  • every 3-4 year event

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