Download Topic 5 Temperature, Pressure, and Moisture

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Temperature,
Pressure,
and Moisture
Mr. Rocco
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Temperature
• As air warms, its density
decreases and it gets pushed up
higher into the atmosphere.
• As it does, pressure falls and
temperature decreases
***The water vapor in this air cools
and condenses to form CLOUDS!!
• Clouds need condensation nuclei for
water droplets to stick to!
Cold Air
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(ALOFT)
• Cold air higher up in atmosphere is
more dense and starts to sink
• As it does, pressure increases and
temperature warms up.( bike tire
pump)
Latent Heat
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As water vapor changes from gas
to liquid, heat is released into
the air.
What’s Latent heat used for?
• The fact that supercells (thunderstorms)
occur where warm, moist air meets
cold, dry air suggests the source of
energy for both t-storm and tornado:
• latent heat is in the warm, moist air.
Latent heat is heat you can't detect with
a thermometer.
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Moisture
• When more moisture(water
vapor) is added to air, the
density and pressure of the
air decreases.
(You would think adding water would make the air
heavier like a wet sponge, right?)
BUT………..
• For each molecule of dry air ( N or O)
that gets replaced by a water molecule,
the air actually becomes less dense.
• Why?
• An N(28) or O(32) dry air molecule
weighs 1.5 to 2x as much as a water
molecule.(Atomic Weight=18)
• So moist air weighs less!!!
DRY AIR
WEIGHS
MORE!!!
MOIST
AIR
WEIGHS
LESS!!!
Air
molecules
Water
molecules
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**Weather Differences**
LOW Pressure: HIGH Pressure:
• Warm/Hot air
• Moist air
• Stormy!!!!
• Cool/Cold air
• Dry air
• Clear,sunny
conditions
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Summing up……..
• As altitude increases, air
density and pressure decrease
• As temperature and moisture
increase, air density and
pressure decrease