Download Various Types of Clouds.

The Numerous Varieties of Clouds
Cloud Types
common cloud classifications
Clouds are classified into a system that uses Latin words to describe the
appearance of clouds as seen by an observer on the ground. The table
below summarizes the four principal components of this classification
system
Latin Root
cumulus
stratus
cirrus
nimbus
Translation
heap
layer
curl of hair
rain
Example
fair weather cumulus
altostratus
cirrus
cumulonimbus
Further classification identifies clouds by height of cloud base. For
example, cloud names containing the prefix "cirr-", as in cirrus clouds,
are located at high levels while cloud names with the prefix "alto-", as in
altostratus, are found at middle levels. This module introduces several
cloud groups. The first three groups are identified based upon their
Cont…
height above the ground. The fourth group consists of vertically
developed clouds, while the final group consists of a collection of
miscellaneous cloud types.
Low Etage
SFC-6500 FT
Low-level Clouds
Low clouds are of mostly composed of water droplets since their bases
generally lie below 6,500 feet (2,000 meters). However, when
temperatures are cold enough, these clouds may also contain ice particles
and snow.
Fair Weather Cumulus Clouds
puffy cotton balls floating in the sky
Fair weather cumulus have the appearance of floating cotton and have a
lifetime of 5-40 minutes. Known for their flat bases and distinct outlines,
fair weather cumulus exhibit only slight vertical growth, with the cloud
tops designating the limit of the rising air. Given suitable conditions,
however, harmless fair weather cumulus can later develop into towering
cumulonimbus clouds associated with powerful thunderstorms.
Nimbostratus Clouds
dark, low-level clouds with precipitation
Nimbostratus are 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 (2,000
meters). However, when temperatures are cold enough, these clouds may
also contain ice particles and snow.
Stratocumulus Clouds
low, lumpy layer of clouds
Stratocumulus clouds generally appear as a low, lumpy layer of clouds
that is sometimes accompanied by weak intensity precipitation.
Stratocumulus vary in color from dark gray to light gray and may appear
as rounded masses, rolls, etc., with breaks of clear sky in between.
•Stratocumulus can be widely scattered, as depicted in this photo, but
are usually concentrated closer together in clusters or layers and have
very little vertical development. This photo of a stratocumulus layer
from above was taken by Jay Shafer, a PSC meteorology graduate,
from Mt. Washington. Jay also went down to a lower elevation and
took another photo providing a closeup, side view of a stratocumulus
cloud in this deck. These relatively flat clouds usually lack the sharp
edges and "popcorn" appearance of most normal cumulus clouds
Layered SC
•Stratus are usually the lowest of the low clouds. Stratus often appear as
an overcast deck (as shown), but can be scattered. The individual cloud
elements have very ill-defined edges compared to most low cumuloform
clouds (e.g. cumulus and stratocumulus).
•Fog can be considered as a low stratus cloud in contact with the
ground. When the fog lifts, it usually becomes true stratus. This photo
shows fog over the Pemigewasset River basin with clear skies
elsewhere
Cumulonimbus Clouds
reaching high into the atmosphere
Cumulonimbus clouds (Cb) are
much larger and more vertically
developed than fair weather
cumulus. They can exist as
individual towers or form a line
of towers called a squall line.
Fueled by vigorous convective
updrafts (sometimes in excess 50
knots), the tops of cumulonimbus
clouds can easily reach 39,000
feet (12,000 meters) or higher.
Lower levels of cumulonimbus
clouds consist mostly of water
droplets while at higher
elevations, where temperatures
are well below 0 degrees Celsius,
ice crystals dominate. Under
favorable atmospheric conditions,
harmless fair weather cumulus
clouds can quickly develop into
large cumulonimbus clouds
associated with powerful
thunderstorms known as
supercells.
Mid Etage
6500 –16500 FT
Mid-Level Clouds
The bases of mid-level clouds typically appear between 6,500 to 13,000
feet. Because of their lower altitudes, they are composed primarily of
water droplets, however, they can also be composed of ice crystals when
temperatures are cold enough
Altocumulus Clouds
parallel bands or rounded masses
Altocumulus may appear as parallel bands (top
photograph) or rounded masses (bottom
photograph). Typically a portion of an
altocumulus cloud is shaded, a characteristic
which makes them distinguishable from the
high-level cirrocumulus. Altocumulus clouds
usually form by convection in an unstable
layer aloft, which may result from the gradual
lifting of air in advance of a cold front. The
presence of altocumulus clouds on a warm and
humid summer morning is commonly followed
by thunderstorms later in the day.
Altocumulus may appear as parallel bands or rounded masses. Typically
a portion of an altocumulus cloud is shaded, a characteristic which
makes them distinguishable from the high-level cirrocumulus.
Altocumulus clouds usually form by convection in an unstable layer
aloft, which may result from the gradual lifting of air in advance of a
cold front. The presence of altocumulus clouds on a warm and humid
summer morning is commonly followed by thunderstorms later in the
day.
•Altostratus have a more uniform and diffuse coverage where it is
difficult to detect individual elements or features. In this picture, a few
altocumulus clouds in the foreground precede a more uniform deck of
altostratus.
High Etage
16500-45000 FT
High-Level Clouds
High-level clouds form above 16,500 feet and since the temperatures are
so cold at such high elevations, these clouds are primarily composed of
ice crystals. High-level clouds are typically thin and white in appearance,
but can appear in a magnificent array of colors when the sun is low on
the horizon.
Cirrus Clouds
thin and wispy
The most common form of high-level clouds are thin and often wispy
cirrus clouds. Typically found at heights greater than 20,000 feet (6,000
meters), cirrus clouds are composed of ice crystals that originate from
the freezing of supercooled water droplets. Cirrus generally occur in fair
weather and point in the direction of air movement at their elevation.
•Cirrocumulus are high clouds that have a distinct patchy and/or
wavelike appearance, such as, in this patchwork cirrocumulus photo,
composed of many individual cloud elements, or may be wavy.
Cirrostratus Clouds
sheet-like and nearly transparent
Cirrostratus are sheet-like, high-level clouds composed of ice crystals.
Though cirrostratus can cover the entire sky and be up to several
thousand feet thick, they are relatively transparent, as the sun or the
moon can easily be seen through them. These high-level clouds typically
form when a broad layer of air is lifted by large-scale convergence.
Sometimes the only indication of their
presence is given by an observed halo
around the sun or moon. Halos result from
the refraction of light by the cloud's ice
crystals. Cirrostratus clouds, however, tend
to thicken as a warm front approaches,
signifying an increased production of ice
crystals. As a result, the halo gradually
disappears and the sun (or moon) becomes
less visible
Orographic and “Specialty” Clouds
CONTRAILS
A contrail, also known as a condensation trail, is a cirrus-like trail of
condensed water vapor often resembling the tail of a kite. Contrails are
produced at high altitudes where extremely cold temperatures freeze
water droplets in a matter of seconds before they can evaporate.
Contrails form through the
injection of water vapor into the
atmosphere by exhaust fumes
from a jet engine. If the
surrounding air is cold enough, a
state of saturation is attained and
ice crystals develop, producing a
contrail.
Mammatus Clouds
sagging pouch-like structures
Mammatus are pouch-like cloud structures
and a rare example of clouds in sinking air.
Sometimes very ominous in appearance, mammatus clouds are harmless
and do not mean that a tornado is about to form; a commonly held
misconception. In fact, mammatus are usually seen after
Photograph by: Manikin
Orographic Clouds
forced by the earth's topography
Orographic clouds are clouds that develop in response to the forced
lifting of air by the earth's topography (mountains for example).
Photograph by: Holle
Pileus Clouds
smooth capping clouds
Pileus (Latin for "skullcap") is a smooth cloud found attached to either a
mountain top or growing cumulus tower.
Photograph by: Manikin
•Cap clouds form when air containing water vapor is uplifted on the
windward slide of the slope and reaches saturation producing liquid
water cloud droplets and a cloud which can "cap" the summit. The
spectacular picture was provided by Michael Nahmias and shows the cap
cloud shrouded summit of Mt. Ranier.
ACLS
Billow Clouds
produced by Kelvin-Helmholtz instability
Billow clouds are created from instability associated with air flows
having marked vertical shear and weak thermal stratification. The
common name for this instability is Kelvin-Helmholtz instability. These
instabilities are often
visualized as a row
of horizontal eddies
aligned within this
layer of vertical
shear.
Credits
Photos and Text Courtesy of:
University of Illinois (Project WW2010)
Ronald L. Holle
Geoff Manikin
Kevin Knupp
Robert M. Rauber
Plymouth State College Meteorology Department
James D. Rufo
Michael H. Nahmias
Mrs. Lorraine Brown
Mark J. Gibbas
Jay Shafer
Bill Schmitz
University of Illinois Cloud Catalog
NOAA Cloud Storm Spotter’s Guide