(c) thermal transfers on Earth

• Atmospheric convection : warm air rises verticaly to the stratosphere and goes down to the ground when the air cooled down.
• The air masses surronding the Earth tend to redistribute heat from the Sun


  A mass of warm ascending air is compensated by a mass of cool descending air. Air mass exchange manifested by wind.
• On a planetary scale, there are three major zones of wind circulation between the equator and the poles
• Hadley cell

  1. Large-scale circulation consisting of warm air that rises near the equator and moves poleward in the upper troposphere creating a low-pressure belt at the equator

  2. As it rises to the top of the troposphere, the air cools to the same temperature as its surroundings and begins to flow toward the north and south poles

  3. The cooled air descends gently again to reach the Earth's surface at around 30 degrees North and 30 degrees South, creating a zone of high subtropical atmospheric pressure

  4. The air thus compressed and heated prevents the formation of clouds, resulting in clear skies, high temperature at the Earth's surface, permanent dry weather, and the formation of large tropical deserts
• On the earth's surface, regular winds blow from the northeast in the northern hemisphere and from the southeast in the hemisphere between the Tropics and the equator, known as the trade winds
• Over the course of the year, Hadley cells in each hemisphere move north and south in response to the Sun's position relative to Earth
• The Ferrel cell is in mid-latitudes where two currents of hot and cold air converge
• Ferrel cell


  Warm air rises above colder air, creating areas of low pressure flowing eastward as the Earth spins
• The polar cells are located north and south of the 60th parallels north and south respectively
• Cold air descending at the poles causes high pressure in the polar regions, leading to surface air migrating towards the mid-latitude low-pressure belts
• Coriolis 


  Imaginary force, wind don't blow in a straight line due to the rotation of the Earth.
• Jet streams


  High altitude winds connecting cells
• Hot desert exist at the tropics because the dry air (cold/heavy) descends & absorbs all clouds. This air masses are part of the Hadley convection cell.
• Arid climate can be found at the pôles because there is not much evaporation/moisture in air, it is cold.