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.