ATOC 181 Lecture Notes - Lecture 12: Altostratus Cloud, Ozone Depletion, Tropopause
7 Jun 2018
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LESSON 12
Fog Precipitation
• Precipitation is falling, under dryer and colder air below the clouds. Evaporation from rain drops and the
water vapour from these rain drops will condense into tiny droplets and fog formed in this air that is
now saturated.
• Liquid drops or ice crystals evaporate or sublimate. When have evaporation, require energy from
atmosphere that cools down?
• Water vapour increases
• At the same time, air is cooled (latent heat is required)
CLOUDS
• Different kinds of clouds
• Cloud is a visible aggregate (visible as little water) of tiny water droplets or ice crystals suspended in the
air
• Size of cloud drops: 5micron- 100 micron
• Clouds vary highly in height, thickness, shape, content (number of droplets, water content)…
• Cloud classification
o Lamarck (1802): 1st attempt of classification
▪ Introduced the 1st cloud classification
▪ French words
▪ Very descriptive
▪ En forme de voile = hazy clouds
▪ Attroupés = massed clouds
▪ Pommelés = dappled clouds
▪ En balayeurs = broom-like clouds
▪ Groupés = grouped clouds
o Howard (1803): modified previous one
▪ Inspired by Carl von Linne
▪ More scientific
▪ Terms refer to shape of clouds
▪ Cumulus (heap)
▪ Stratus (layer)
▪ Cirrus (curl of hair)
▪ Nimbus (rain)
o Abercromby and Hildebrandsson (1887)
▪ Clouds today are classified in 10 principal clouds forms
VIDEO
• Indicator of weather patterns
• Structural characteristics and height in atmosphere where they develop
• Cirrus: can mimic strands of height, high levels of clouds, indirect indicator of weather patterns,
troposphere
• Cumulo (heap, pile): look detached, fluffy, cotton balls, low level clouds,
• Strato: layers of clouds, hazy white or grey mass, low clouds, can also be observed in mid height.
find more resources at oneclass.com
find more resources at oneclass.com
• Cirrostratus: high level
• Nimbo (rains): hybrid, nimbostratus
• Stratocumulus:
WMO Cloud Classification
• Adopted the current cloud classification using:
o Latin words to describe height and appearance
o Factors according to:
▪ Height: low, mid, high, vertical
▪ Appearance: shape, density, colour
• Three types of high clouds:
o prefix: cirro
o Cirrus: delicate streaks or patches
o Cirrostratus: transparent thin white
sheet or veil
▪ stratus means in layer,
▪ continuous usually,
▪ no holes.
▪ Difference between
cirrostratus (22o halo due to ice
crystals that are scattering light
coming from sun) and
altostratus (no halo as liquid
water does not produce any)
o Cirrocumulus: appears little, little
cotton balls, ice clouds
▪ Layer of small white puffs or
ripples
o Made of ice
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lesson 12: precipitation is falling, under dryer and colder air below the clouds. Evaporation from rain drops and the water vapour from these rain drops will condense into tiny droplets and fog formed in this air that is now saturated: liquid drops or ice crystals evaporate or sublimate. When have evaporation, require energy from atmosphere that cools down: water vapour increases, at the same time, air is cooled (latent heat is required) Introduced the 1st cloud classification: french words, very descriptive, en forme de voile = hazy clouds, attroup s = massed clouds, pommel s = dappled clouds, en balayeurs = broom-like clouds, group s = grouped clouds, howard (1803): modified previous one. Inspired by carl von linne: more scientific, terms refer to shape of clouds, cumulus (heap, stratus (layer, cirrus (curl of hair, nimbus (rain, abercromby and hildebrandsson (1887, clouds today are classified in 10 principal clouds forms.
