Weather

Weather

1. Temperate

   • Depressions/Low/Cyclones
     • low-pressure frontal systems
       • dominated between clash of cold polar air and warm subtropical masses
       • along the front are warm air waves with a following cold front
         • due to Coriolis force they can turn into a depression
     • Life span of 4-7 days covering 15,00-3000km diameter
     • key feature - both warm and cold front can bring rain
       • warm air has more moisture, chilled by the cold air it forms clouds and then rain
   • High-pressure systems
     • warm subtropical high pressure systems bring clear skies and sunny weather
       • Coriolis force means these light winds (associated with high pressure systems) move clockwise in northern hemisphere and thus oppose easterly velocity of the frontal system
         • Thus, acting as a blocking system that can last many days

2. Tropical

   • Inter-tropical convergence zone
     • ITCZ dominates tropical weather
     • This is where trade wind systems of both hemispheres converge due to the Coriolis force.
     • forms because of the intense solar heating of the tropics and mass evaporation causes air with moisture to rise, the low pressure causes it to cool reducing its ability to hold water and thus form clouds.
       • This is why the tropics have huge towering columns of clouds which produce very intense convectional rainfall
   • Monsoons
     • derived from the Arabic word 'mausim' meaning season
     • Most of the rain in southeast Asia falls in summer
     • As winds are always defined by the direction from which they are coming one can tell where the monsoon originates e.g. the southwest monsoons start there and move towards the northeast etc
     • In summer the intense heating of Asia causes air to rise which lowers air pressures allow winds from the south to be sucked in from across the equator.
       • This creates the opposite effect of the Coriolis force in the northern hem changing direction by over 90 degrees resulting the southwest monsoons.
         • these winds are warm and by travelling across the indian and pacific oceans they contain a lot of moisture.
           • As they pass over land they are forced to rise causing them to cool and give their moisture up in the form of torrential rain - the monsoons.