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Daytime versus Nighttime Cloud Temperature
Name: John
Status: student
Grade: 4-5
Location: NC
Country: USA
Date: N/A
Question:
Are clouds in the day warmer then the clouds at night? Why
or why not?
Replies:
Urban areas with their cover of concrete and/or asphalt are believed to
cause local changes in cloud cover, relative humidity, and low level air
temperature and pressure. That the effect is so large that it would affect
the jet stream is a unlikely extrapolation. There are just too many other
things also happening. In addition, the "natural landscape" is not inert.
It too is exchanging heat energy, and light (electromagnetic radiation)
with the atmosphere.
Vince Calder
John,
In general, clouds may be slightly warmer during
the day than at night. However, the difference in
temperature between day and night may be very small,
as their temperature is more affected by the air
surrounding them and physical processes that take
place within the cloud (such as convection, divergence,
etc., which require more of an explanation here than
this question demands).
The tops of clouds are warmer in the
day than during the night, simply because
they're receiving energy from the Sun
during the day.
Judging the warmth of the bottom and inside of
the cloud during day and night is far more
complicated and depends on several factors,
including cloud height, cloud density, and whether
you're talking about a layer of cloud or partly
cloudy conditions.
Assuming that there is only one cloud layer, the
height of the cloud will affect how much energy its base
receives from a) solar radiation that has penetrated through
the cloud, b) solar radiation that has been reflected
by the ground, and c) terrestrial radiation (energy
radiated by the ground). If the cloud base receives less
energy from these sources at night than during the day,
then it will be cooler at night. This would be normal.
During nighttime, clouds radiate energy both from their top
and their base, thereby cooling overall, although the
cloud base can still be warmed significantly by terrestrial
energy.
If there are multiple cloud layers, the warmest one can
contribute to warming the other ones, although minimally.
David R. Cook
Meteorologist
Climate Research Section
Environmental Science Division
Argonne National Laboratory
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Update: June 2012
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