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CLOUDS:
• A cloud is a visible aggregate of tiny water droplets
and/or ice crystals suspended in the atmosphere
• They can exist in a variety of shapes and sizes.
• Some clouds are accompanied by precipitation; rain,
snow, hail, sleet, even freezing rain.
Condensation Nuclei
• Tiny particles (dust, salt) which stimulate
droplet formation
• Water is known to exist
in three different states;
as a solid, liquid or gas.
• Clouds, snow, and rain
are all made of up of
some form of water.
• A cloud is comprised of
tiny water droplets
and/or ice crystals
• A snowflake is an
aggregate of many ice
crystals
• Rain is just liquid
water.
• Water existing as a gas is
called water vapor.
• When referring to the
. in the
amount of moisture
air, we are actually
referring to the amount of
water vapor.
• If the air is described as
"moist", that means the air
contains large amounts of
water vapor.
• Common sources of
moisture are the Maritime
Air masses.
• A cloud naming system was invented in 1802 by Luke
Howard.
• 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
Translation
Example
cumulus
stratus
cirrus
nimbus
heap
layer
curl of hair
rain
fair weather cumulus
altostratus
cirrus
cumulonimbus
Classifying Clouds
• Clouds are classified according to their
form and altitude.
The three main forms: stratus clouds,
cumulus clouds and cirrus clouds.
The three altitude groups:
low clouds (up to 2000m)
middle clouds (2000 – 6000m)
high clouds (above 6000m)
Stratus Clouds
- flattened, layered shape
- cover large areas of sky
- usually form when a warm air mass overruns a cold
air mass
- indicate stable conditions
Cumulus Clouds
- puffy, “heaped” shape
- created by convective or frontal cloud formation
- usually indicate unstable weather
Cirrus Clouds
- thin, wispy clouds
- the highest clouds in the sky
- created by wind blown ice crystals
- usually indicate fair weather
• One more cloud sub-classification is
the word nimbus indicating a rain
carrying cloud
Alto = mid-level cloud
High-Level Clouds
• Cirrus - high-level clouds
form above (6,000 meters)
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. They move
across the sky on bright
sunny days. Cirrus clouds
mean warm air is on the way.
Cirrus - high-level clouds
Mid-Level Clouds
• The bases of mid-level
clouds typically appear
between 2,000 to 6,000
metres. Alto- clouds,
because of their lower
altitudes, are composed
primarily of water
droplets, they can also be
composed of ice crystals
when cold enough.
Altocumulus Clouds
parallel bands or rounded masses
Low-level Clouds
• Low clouds are
mostly composed of
water droplets since
their bases generally
lie below 2,000
meters. When cold
enough, these clouds
may also contain ice
particles and snow.
Nearly all low
clouds are some
form of stratus
cloud.
Nimbostratus Clouds
dark, low-level clouds with precipitation
Stratus Clouds
Fair Weather Cumulus Clouds
puffy cotton balls floating in the sky
• Fair weather cumulus
have the appearance of
floating cotton with flat
bases have a lifetime of 540 minutes. The cloud
tops designates the limit of
the rising air. Given
suitable conditions,
however, harmless fair
weather cumulus can
develop into
cumulonimbus clouds
associated with
thunderstorms.
Cumulus Clouds
Classification of Clouds Sheet
Label the diagram with the correct
name at the appropriate altitude
Stratus
Stratus
http://images.google.ca/images?q=tbn:IhT6BeU74SwJ:http://www.cen
tennialofflight.gov/2003FF/clues/clipart/stratus.jpg
Stratus
Nimbostratus
Nimbostratus
Cumulus
Cumulus
Cumulus
Stratocumulus
Altostratus
Altocumulus
Cumulonimbus
Base of cloud
Cumulonimbus
Cumulonimbus
http://epod.usra.edu/archive/images/cumulonimbus_052301_sjr.jpg
Cirrocumulus
Cirrostratus
Cirrocumulus
Cirrus
Cirrus
Nimbus
A few interesting clouds………
Mammatus clouds
Form below the anvil of a thunderstorm
Usually seen with storms that produce
tornadoes….
Strange Clouds….
UFO?
More “UFO’s”….
Rain or Snow?
dependent upon temperature
• Precipitation typically forms high in the atmosphere where the
temperature is below freezing. As ice crystals form aloft and fall
toward the surface, they collect each other to form large
snowflakes. If ground temperature is above 0C, the freezing level
must be located somewhere above the ground. As the falling snow
passes through the freezing level into the warmer air, the flakes
melt and collapse into raindrops. During the summer months, it is
not uncommon for the freezing level to be found at a level above
cloud base.
0C
0C
• When the air temperature at the ground is less than 0C,
the snowflakes do not melt on the way down and
therefore reach the ground as snow.
0C
0C
Rain and Hail
• Rain develops when
growing cloud droplets
become too heavy to
remain in the cloud and
as a result, fall toward
the surface as rain. Rain
can also begin as ice
crystals that collect each
other to form large
snowflakes. As the
falling snow passes
through the freezing
level into warmer air, the
flakes melt and collapse
into rain drops.
• Hail is a large frozen raindrop
produced by intense
thunderstorms. As the
snowflakes fall, liquid water
freezes onto them forming ice
pellets that will continue to
grow as more and more
droplets are accumulated.
Upon reaching the bottom of
the cloud, some of the ice
pellets are carried by the
updraft back up to the top of
the storm where they will
repeat the growth steps. When
the stones are too heavy for
the updraft, the stones fall.
Freezing Rain
• Ice storms can be the most
devastating of winter weather
phenomena and are often the
cause of automobile accidents,
power outages and personal
injury. Ice storms result from
the accumulation of freezing
rain, which is rain that becomes
supercooled and freezes upon
impact with cold surfaces.
• Freezing rain develops as
falling snow encounters a
layer of warm air deep enough
for the snow to completely
melt and become rain. As the
rain continues to fall, it passes
through a thin layer of cold air
just above the surface and
cools to a temperature below
freezing. The drops do not
freeze, a phenomena called
supercooling occurs
("supercooled drops“ form).
When the supercooled drops
strike the frozen ground
(power lines, or tree
branches), they instantly
freeze, forming a thin film of
ice, hence freezing rain.
Snow
• Snowflakes are simply
aggregates of ice crystals that
collect to each other as they fall
toward the surface. The diagram
shows a typical temperature
profile for snow with the red
line indicating the atmosphere's
temperature at any given
altitude. The vertical line in the
center of the diagram is the
freezing line. Temperatures to
the left of this line are below
freezing, temperatures to the
right are above freezing. Since
the snowflakes do not pass
through a layer of air warm
enough to cause them to melt,
they remain in tact and reach
the ground as snow.