Cloud Formation

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Cloud Formation
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Figure 17.2
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Figure 17.10
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Convective Lifting
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Orographic Lifting
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ConvergentLifting
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Frontal Lifting
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Frontal Lifting
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Figure 17.7
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Figure 17.21A
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Stratus
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Figure 17.21G
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Figure 17.21H
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Figure 17.20 (left)
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Figure 17.20 (right)
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Fog
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RadiationFog
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Advection Fog
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Upslope Fog
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Evaporation Fog ex. Steam Fog
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How precipitation forms.
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Precipitation in Cold vs. Warm clouds
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Bergeron Process
An important thing to note is that Cloud Droplets
do not freeze at 0degrees C. Rather,
they do not free until about -40 degrees C
(-40F) Water that is below 0 degrees C is
SUPERCOOOLED. Supercooled water will freeze
easily if it comes in contact with an object.
Supercooled water will freeze on contact with
solid particles that have a crystalline
structure. These objects are known as FREEZING
NUCLEI (similar to condensation nuclei necessary
for condensation). Freezing nuclei are not as
plentiful in the atmosphere as condensation
nuclei are.
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Bergeron Process continued
At temperatures between 0 and -10C, clouds are
composed primarily of supercooled water
droplets At temperatures between -10C and -20C,
there are liquid water droplets ice
crystals At temperatures below -20C, clouds are
composed mainly of ice crystals. Another
important point The saturation vapor pressure
above ice crystals is somewhat lower than above
supercooled water droplets.
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Bergeron Process
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Collision Coalescence
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Forms of PrecipitationRain
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Snow
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Figure 17.28
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hailstone
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Figure 17.29A