NEWTON:Temperature, Pressure, and Climate Zones
 
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Name: Megha
Status: student
Grade: 9-12
Country: India
Date: Spring 2014


Question:
"Temperature and pressure are directly proportional to each other. This means that as the temperature decreases, the pressure also decreases, and as the temperature increases, the pressure increases." However, if we look at the Pressure Belts, the Equatorial Region has high temperature BUT low pressure; the Polar Regions have high pressure BUT low temperature. The two facts contradict each other.


Replies:
Megha,

Actually, temperature (T) is proportional to pressure (P) and volume (V), as in the ideal gas law, PV=nRT. nR is essentially a constant.

So, if you kept the volume of air constant, temperature would increase proportionately with a increase in pressure, and temperature would decrease proportionately with a decrease in pressure.

But the atmosphere is much more complicated than that. Normally T, P, and V vary depending more on external forcings, such as heating by solar radiation, cooling at night from radiative losses to the sky, the pressure wave that accompanies sunrise (pressure increases around sunset as the warmed atmosphere to the east expands and pushes towards the west), atmospheric weather systems (which tend to have properties almost independent of and varying with their movement) invade or leave the area, etc.

So, you can have both cold temperatures and low pressure (or high pressure) at the poles and hot temperatures and high pressure (or low pressure) at the equator, depending on the meteorological and radiological situation at the time.

David R. Cook Meteorologist / Team Lead Atmospheric and Climate Research Program Environmental Science Division Argonne National Laboratory


The first statement is for gas in a container, the second is for gas in our relatively uncontained atmosphere.

Basically, in a container heated gas tries to expand but cannot do so because of the walls of the container hold it in: pressure increases. But in the atmosphere the gas can expand as far as it wants with only gravity holding it down.

Not only is the atmosphere higher at the equator, the atmosphere rises and shrinks daily where we are as we go from daytime to night and back again.

Bob Avakian Oklahoma State University Institute of Technology


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