Temperature Change with Elevation

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Temperature Change with Elevation
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We know that it gets colder as you go up a
mountain.
Conversely, it gets warmer as you go down a
mountain.
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Sometimes it doesnt matter where you are on a
mountain, it can get very hot!
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Why does air change temperature with
elevation? Because as air rises there is less
atmospheric pressure (there is less atmosphere
above it) so the air molecules are more spread
out. Similarly, as air descends it warms up
because there is more atmospheric pressure and
the air molecules are closer together. Air warms
up and cools down at a constant average rate of
1C for every 100 meters of elevation
change. This is called the lapse rate. Simple
right?
http//apollo.lsc.vsc.edu/classes/met130/notes/cha
pter1/graphics/column.free.gif
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http//www.geog.ucsb.edu/joel/g110_w07/lecture_no
tes/cooling_processes/agburt05_13ab.jpg
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The latent (hidden) heat of evaporation To
evaporate water requires heat energy.
As the water evaporates, the energy that is used
to evaporate it is stored in a hidden (that is,
latent) form in the water vapour. Remember as
well that water vapour is invisible. So, is that
water vapour above the pot? NO! Its visible so
it cant be! Steam is made up of tiny drops of
liquid water. The water vapour is condensing as
soon as it gets above the water. This is
important to remember when we consider clouds.
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Heres the tricky part When water vapour
condenses back to a liquid form, the heat that
was used to evaporate the water is released back
into the air. (Thats why, if you put your hand
in the steam right above a pot of boiling water,
it can be easily burned.) So, as air rises up in
the atmosphere it cools at a constant rate of 1C
for every 100 meters until the water vapour
starts to condense. Then the heat that was used
to evaporate the water (called the latent heat of
evaporation) is released to the air and the
cooling rate changes to only 0.6C for every 100
meters.
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This is how it works
Paulies temperature at sea level was 20. Paulie
has gone up 800 m. Therefore, Paulies
temperature has dropped 8 and Paulies
temperature is now 20 - 8 12
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This is how it works
Paulie went from the condensational elevation to
the top of the mountain and he cooled down 0.6
for every 100 meters, so 1500 800 700
meters from the CE to the top. Therefore,
Paulies temperature dropped 7 x 0.6 4.2 from
the CE to the top. If Paulies temperature at the
CE was already 12, then his temperature at the
top was 12 - 4.2 7.8
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This is how it works
Paulie goes down 700 meters from the top of the
mountain to the condensation elevation. Therefore,
he will warm up by 7. Paulies temperature at
the condensation elevation will be 7.8 7
14.8
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This is how it works