Meteorology: Clouds

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Meteorology Clouds
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Clouds

• A cloud is a visible aggregate of tiny water
  droplets and/or ice crystals suspended in the
  atmosphere
• Exist in a variety of shapes and sizes.

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Cloud Coverage

• No ceiling
• CLR Clear Sky
• FEW 1/8 to 2/8 of the sky covered.
• SCT Scattered, 3/8 to 4/8 covered
• Ceiling
• BRK Broken, 5/8 to 7/8 covered
• OVC Overcast, 8/8 covered

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Clouds form by

• 1. Adding Water Vapor into the Air
• 2. Mixing Warm Moist Air with Cold Air
• 3. Lowering the Air Temperature

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Clouds Classification

• Classified into a system that uses Latin words.
• Describe the appearance of clouds, and,
• Describe the approximate altitude.

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Cloud Classification (2)

• High Clouds
• Middle Clouds
• Low Clouds
• Vertical development Clouds
• Orographic Clouds

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High Clouds

• 20,000 to 40,000 ft
• Types
• Cirrus (CI)
• Cirrostratus (CS)
• Cirrocumulus (CC)

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Cirrus (CI)

• High and Wispy
• Typically found at heights greater than 20,000
  feet (6,000 meters),
• Generally occur in fair weather and point in the
  direction of air movement at their elevation.
• Made of ice crystals.

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Cirrus (2)
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Cirrostratus (CS)

• Sheet-like, high-level clouds composed of ice
  crystals
• Cirrostratus clouds, however, tend to thicken as
  a warm front approaches, signifying an increased
  production of ice crystals.

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Cirrostratus (2)
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Cirrocumulus (CC)

• Some what rare
• Appears as a white sheet with a pebbly patter.
• Characterized by high ice crystals.

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Cirrocumulus (2)
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Middle Clouds

• 6500 to 20,000 ft
• Types
• Altostratus (AS)
• Altocumulus (AC)
• Altocumulus Castellanus(ACC)

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Altocumulus (AC)

• Altocumulus clouds on a warm and humid summer
  morning is commonly followed by thunderstorms
  later in the day.

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Altocumulus (2)
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Altostratus (AS)

• Layer cloud with no definite pattern
• Steely of bluish in color
• Sometimes the sun or moon can be seen dimly
  through.
• Altostratus clouds make the sun seem to appear to
  be behind heavily frosted glass.

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Altostratus (2)
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Alto Cumulus Castellanus (ACC)

• Created from instability associated with air
  flows having marked vertical shear and weak
  thermal stratification.

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Low Clouds

• Surface to 6500
• Types
• Stratus (ST)
• Nimbostratus (NS)
• Stratocumulus (SC)
• Stratus Fractus (SF)
• Cumulus Fractus (CF)

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Stratus (ST)

• Low layer cloud
• Resembles fog but does not rest on the ground.
• No waves or patterns gray

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Stratus (2)
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Nimbostratus (NS)

• Dark, low-level clouds accompanied by light to
  moderately falling precipitation.
• Low clouds are primarily composed of water
  droplets since their bases generally lie below
  6,500 feet

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Nimbostratus (2)
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Stratocumulus (SC)

• Low, lumpy layer of clouds
• Sometimes accompanied by weak intensity
  precipitation.

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Stratocumulus (2)
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Stratus Fractus (SF)

• Stratus torn by wind in fragments
• Drizzle may fall from it.

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Cumulus Fractus (CF)

• Stratocumulus torn by wind

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Clouds of Vertical Development

• Cumulus (CB)
• Towing Cumulus (TCU)
• Cumulonimbus (CB)

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Fair Weather Cumulus (CU)

• Appearance of floating cotton and have a lifetime
  of 5-40 minutes.
• Given suitable conditions, however, harmless fair
  weather cumulus can later develop into towering
  cumulonimbus clouds associated with powerful
  thunderstorms.

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Cumulus (2)
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Towering Cumulus (TCU)

• Growing cumulus tower cloud
• On the way to becoming a Cumulonimbus

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Towering Cumulus (2)
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Cumulonimbus (CB)

• Cumulonimbus clouds are much larger and more
  vertically developed than fair weather cumulus.
• Fueled by vigorous convective updrafts (sometimes
  in excess 50 knots), the tops of cumulonimbus
  clouds can easily reach 39,000 feet

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Cumulonimbus (2)
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Mammatus

• Strong cumulonimbus clouds can have appendages
  protruding from the base of the cloud, which are
  called Mammatus clouds.
• They indicate that the atmosphere is quite
  unstable and can also be an indicator of
  impending severe weather.

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Mammatus (2)
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Orographic Clouds

• Develop in response to the forced lifting of air
  by the earth's topography (mountains for
  example).

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Mountain Wave
Lenticular Clouds
Cap Cloud
Rotor Clouds
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Lenticular Clouds

• Forms in the wave crest very high and hundreds of
  miles long.

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Lenticular Clouds (2)
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Roll/Rotor clouds

• Form downwind from each wave crest.
• Dissipating and forming at the same time due to
  the rotation of the air.

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Cap cloud

• Lies over the top of the mountain and extends
  partially down the leeward slopes, indicates an
  extremely strong downdraft

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Contrails

• Cloud can be formed from the vapor contained in
  the exhaust of a jet engine of an airplane when
  they are flying at high enough altitudes where
  cold temperatures cause the vapor to turn into
  ice crystals like cirrus clouds.

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Contrails (2)