Clouds 1

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Clouds 1
Cloud Types
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Clouds Introduction

• Clouds can assume a variety of shapes, sizes
  and can occur near the surface or at high
  altitudes - most occur in the troposphere.
• Clouds can contain liquid droplets, ice crystals
  or a mixture of the two.
• Clouds can be thick or thin, and have high or low
  liquid water content.
• The first classification system divides clouds
  into 4 basic categories

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Cloud Classification

• Cirrus
• thin, wispy clouds of ice
• Stratus
• layered clouds

• Cumulus
• clouds having vertical development
• Nimbus
• rain-producing clouds

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Clouds - current classification

• High Clouds
• cirrus, cirrostratus, and cirrocumulus
• Middle Clouds
• altostratus and altocumulus
• alto middle
• Low Clouds
• stratus, stratocumulus, and nimbostratus
• Clouds with extensive vertical development
• cumulus and cumulonimbus

• Modification of previous 4 categories that allows
  new combinations
• Results in 10 principal types of clouds which are
  grouped according to their height

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Clouds

• HIGH
• Generally above 6000m
• composed of ice crystals
• re average temp decreases from 15C at a rate of
  6.5C/1000m
• Note definition of high clouds temperature
  dependent
• such clouds can occur as low as 3000m

• MIDDLE
• Between 2000 and 6000m
• usually composed of liquid droplets
• when viewing sun / moon - bright spot
• often gray in color

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Clouds

• LOW
• Bases below 2000m
• stratus form when extensive areas of stable air
  are lifted
• low water content
• between 0.5 to 1 km thick but can extend for
  large horizontal areas
• may also be a result of turbulence associated
  with strong winds

• If yield precipitation?
• Nimbostratus (light)
• stratocumulus?
• Have some vertical development
• key - thicker sections appear dark
• thinner appear as bright spots

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Clouds

• Cumulus humilis (fair weather)
• single plume of rising air
• no precipitation
• Cumulus Congestus
• multiple towers
• several cells of uplift continually forming and
  dissipating every 10s of min
• have large temp differences from top to bottom
• even on hot days upper portions can have
  subfreezing temperatures
• Cumulonimbus

• VERTICAL DEVELOPMENT
• Cumuliform
• updrafts in certain cumuliform clouds can be more
  rapid than the horizontal winds found in weak
  hurricanes
• liquid water content very much greater
• Cumulus clouds fall into several subgroups