Geography - physical environments

• Air pressure


  There are two types: low pressure (depressions) and high pressure (anticyclones)
• Fronts


  1. Occur on low pressure areas (depressions)

  2. Isobars are close together on low pressure areas, bringing strong winds

  3. The number on the isobars decreases towards the centre

  4. Depressions always bring rain as fronts give us rain
• High pressure areas


  • Called anticyclones
  • Isobars are far apart, bringing gentle winds
  • The number on the isobars increases towards the centre
  • Winds blow away from high pressure
• The closer the isobars


  The stronger the winds
• Winds blow roughly parallel to the isobars


  Winds blow towards low pressure
• Types of fronts


  • Warm fronts
  • Cold fronts
  • Occluded fronts
• Warm fronts


  Bring steady rain as warm air rises over cold air
• Cold fronts


  Bring heavy rain and strong winds as cold air pushes under warm air
• Occluded fronts


  Bring torrential rain as a cold front overtakes a warm front
• Low pressure


  • Depressions
  • Winds circulate in an anticlockwise direction
  • Strong winds - isobars close together
• Cloudy at fronts


  • Heavy rain at a warm front/cold front
  • Warmer and drier on the warm sector
  • Warmer as the warm front approaches and passes
  • Can be warmer as the clouds trap the heat
• High pressure


  • Anticyclone
  • Winds circulate in a clockwise direction
  • Light winds - isobars are far apart
  • Dry weather
  • Clear skies/Little cloud since air sinks (no precipitation)
  • Hot in summer
  • Cold (below freezing) in winter due to lack of cloud which allows heat to escape
  • Fog blocks out sunlight
• Low pressure characteristics on a synoptic chart

  • Isobars close together
  • Fronts present bring rain & cloud
  • Anti-clockwise wind direction
  • Always moves eastwards