Clouds and storms

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ATOC 4720 class24

• Clouds and storms
• 1. Extratropical cyclonic storms
• 2. Artificial modification of clouds and
  precipitation

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Previous Cloud morphology
One type stratus clouds Mechanism?
Z 0-10km (tropopause) X-Y hundreds or thousands
of square kilometers 10th of hours A few 10th of
g/cm3 Lifting rate a few cm/s Often occur in
extratropical regions
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Where is the lifting force from?
In extratropics, this large-scale ascending of
warm air is often associated with the
development of cyclones, which is associated
with the approach of a warm (or cold) front.
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1. Extratropical cyclones cold front and warm
front
Occluded front
Cold air
Warm front
Warm
Cold front
Sharp temperature gradient region front
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Vertical structure along A-B
A
B
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Vertical structure both warm and cold fronts
lean backward
Cold front
Warm front
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• Cirrus clouds

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Cirrostratus halos
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Deposition on ice nuclei Different from
convective clouds
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2. Artificial modification of clouds
Cloud microphysics Warm cloud collision and
coalescence
Cold cloud deposition and then
riming and
aggregation
According to these ideas modify clouds

• Seeding introduce hygroscopic particles or water
  drops in warm
• clouds
• Seeding artificial ice nuclei into cold clouds
  (1/liter)
• Introduce relatively high concentration of
  artificial ice nuclei
• into cold clouds (to reduce the
  concentration of supercooled
• water and therefore inhibit the growth)

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Dry ice (-78C more efficient in dissipating
clouds) Silver iodide (-10C)
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Artificial modification of Precipitation
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Evaluation

• Physical
• Statistical