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Hands-On, Minds-On Meteorology
Description
| Programming | Operation
Water
Collisions
Description
A brief description of what happens when water vapor / liquid is in
ParcelSet* and has the opportunity to either evaporate or condense.
Programming
Theory
The theory for collisions between water elements (vapor and\or liquid)
is as follows:
If both colliders are water elements and the relative humidity of
the parcel is > 100%, they will condense. If the RH = 100%, then
a check is made and condensation will only occur when both water elements
are themselves already condensed (to conserve the RH)
If the RH < 100%, and any condensed water contacts anything, one
vapor molecule is evaporated into the air.
Assumptions
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Relative Humidity
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Collision Possibiilites |
> 100%
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= 100%
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< 100%
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1 dry, 1 anything else |
Bounce
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Bounce
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Bounce
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1 vapor, 1 vapor |
Condense*
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Bounce
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Bounce
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1 vapor, 1 water |
Condense*
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Bounce
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N/A
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1 water, 1 water |
Coalecse
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Coalecse
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N/A
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* Indicates condensation only if it does not drop
the RH below 100%, otherwise, it will bounce (see other, below). |
Equations
N/A
Other
Considering the program only deals with a discrete number of water
elements, the addition of one element can increase the RH from less
than 100% to more than 100%. In such cases, that is rounded down to
100%. This is what is meant by 100%. Also, even if percentage-wise,
there should be 0 molecules, one remains single and the RH = 100%.
This only occurs for extremely cold conditions. Also, this process
is reversible. Rain never occurs on the reasoning that the liquid
water droplets never get large enough.
Operation
Running the Program
This is simply a section of ParcelSet*. Neither this nor ParcelSet*
are directly executable.
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Department of Atmospheric Sciences
University of Illinois at Urbana Champaign
Created by Dan Bramer: Last Modified 07/27/2004
send questions/comments to bramer@atmos.uiuc.edu
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