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  • Wind & Ocean Currents
    • WINDS
      • Process
        • 1. at equator the sun warms the earth which transfers heat to air above causing it to rise.
          • rising air=low pressure, clouds and rain. Called ITCZ(low pressure zone of rising air)
            • ITCZ: Changes according to seasons
              • 21st June sun directly above Tropic of Cancer= ITCZ North of Equator
              • 21st December Above Tropic of Capricorn= ITCZ moves into Southern Hemisphere
        • 3. 30o North and South of Equator the cool air sinks creating high pressure sub-tropical jet streams
        • 4. The cool air reaches the ground surface and moves as surface winds either back to equator or towards the poles
          • surface winds blowing towards the equator are called trade winds
            • They blow from the SE in southern hemisphere and from the NE in northern hemisphere
              • At the equator these trade winds converge in the ITCZ and are heated by solar radiation
                • causes them to rise, condense and form clouds
          • Surface winds blowing towards the poles are called westerlies
            • they blow from NW in southern hemisphere and SW in northern hemisphere
        • 6. Some of the air joins Ferrel Cell and moves back towards the equator and the rest joins polar cell and moves towards poles
        • 5. 60o North and South of Equator
          • warmer surface winds meet cooler air from poles
            • warmer air is less dense than cold air so it rises creating low pressure
        • 7. At the poles the cool air sinks creating high pressure. The high pressure air us drawn back towards equator in surface winds
    • OCEANS
      • Ocean currents are large scale movements of water caused by different water density
        • Density depends on water temp. and salinity
      • currents affected by surface winds, position of land masses and other currents
      • Ocean currents  transfer heat energy from warmer to cooler regions
        • warm ocean currents raise air temp. which warns land nearby
        • cool ocean currents lower air temp, which cools land nearby
      • Ocean currents form giant loops that travel clockwise in northern hemisphere and anticlockwise in southern hemisphere
        • because of surface winds
      • Affect the climate
        • Gulf stream: carries warm water from Caribbean Sea across Atlantic to Western Europe
          • Water in gulf stream cools in northern hemisphere and becomes more dense
            • some of it sinks and is carried back to equator by Canary current which colls west coast of Africa


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