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