        Atmospheric Circulation and More
 
         The global energy balance and atmospheric motion mainly determine 
 the circulation of the earth's atmosphere.  There is a hierarchy of motion 
 in atmospheric circulation.  Each control can be broken down into smaller 
 controlling factors.  The global energy balance is an equal balance of 
 short-wave radiation coming into the atmosphere and long-wave radiation 
 going out of the atmosphere.  This is called thermal equilibrium.  The 
 earth is at thermal equilibrium; however, there can have a surplus or 
 deficit of energy in parts of the heat budget.  If you have a net 
 radiation surplus warm air will rise, and a net radiation deficit will 
 make the air cool an fall.  Air gets heated at the equator because of the 
 inter tropical convergence zone and rises to the poles.  There the air is 
 cooled and it floats back down to the equator where the process is 
 repeated.  Another major contributing factor to the circulation of the air 
 is due to the subtropical highs.  These highs like the ITCZ migrate during 
 the different seasons.  
         The idealized belt model is a great representation of the general 
 circulation of the atmosphere.  The equatorial belt of variable winds and 
 calms ranges from 5 degrees north to 5 degrees south.  This wind belt is 
 characterized by weak winds and low pressure from the inter tropical 
 convergence zone.  As you go further north or south you encounter the 
 Hadley Cells.  Hadley cell circulation is caused by the movement of high 
 pressure from the latitudes at 5 to 30 degrees north and 5 to 30 degrees 
 south to low pressure areas around the equator. 
         The movement of air from high pressure to low pressure causes 
 convergence.  This convergence generates the production of wind.  The 
 winds that are produced from this are the trade winds.  The winds blow 
 from a northwest direction in the northern hemisphere, and in the southern 
 hemisphere the winds blow from a southeast direction.  The trade winds are 
 the largest wind belt.  The westerlies, they lie between 35 and 60 degrees 
 north and south latitude.  The wind blows from the west , thus their name. 
  The westerlies are in the Ferrell cell.  Cold air from the polar regions 
 falls down and then is heated up and pushed upward with the westerlies.  
 >From 65 to 90 degrees north and south lie the polar easterlies.  It exists 
 because of the pressure gradient that is created by the temperatures.  The 
 winds are also deflected by the coralias effect.  This deflection air is 
 to the right in the northern hemisphere, and to the left in the southern 
 hemisphere.  The reason that this happens is because of the rotation of 
 the earth on its axis.  
         Two moving patterns of the general circulation of the atmosphere 
 are the cyclones and anticyclones.  Cyclones are low pressure systems 
 characterized by converging and rising air.  On the other hand 
 anticyclones are characterized by high pressure because they have 
 diverging air that is descending.  There are also land and sea breezes 
 which are produced by daily differences in cooling and heating of the land 
 and water.  Sea breezes bring cooler air in the day, while land breezes 
 push cooler air over the water at nighttime.  
         There also exists radiation surpluses and deficits through out the 
 earth.  There is a constant surplus between the latitudes of 15 degrees 
 north and 15 degrees south.  In the latitudes between 15 and 38 degrees 
 north and south there is a net radiation surplus that varies annually.  
 There is a net radiation deficit annually in the latitudes from 38 to 90 
 degrees north and south.  These surpluses and deficits are due to the high 
 sun angle in the low latitudes, as well as the increased length of 
 daytime.  
         Finally the seasons of the earth are determined by the tilt of the 
 earth on its axis.  The earth is on a tilt of 23.5 degrees.  When it 
 revolves around the sun the earth is exposed to the sun at different 
 degrees at different months of the year.  Because of this phenomenon we 
 get seasons on the earth.  The earth and all of its circulation patterns, 
 energy balances, and motions of the atmosphere are all very complex; 
 however, it can be easily understood by my wonderful summary.          
 
 