Clouds are not made of cotton

1
Clouds are not made of cotton
Mount Hood Lenticular Cloud
2
General Cloud terms
Latin Root Translation Example
cumulus heap fair weather cumulus
stratus layer altostratus
cirrus curl of hair cirrus
nimbus rain cumulonimbus
3
Cloud Classification

• 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 height above the ground. The fourth group
  consists of vertically developed clouds, while
  the final group consists of a collection of
  miscellaneous cloud types.

4
Cloud Classifications

• High clouds - have bases above 18,000 feet
• Middle clouds - have bases between 7,000 and
  18,000 feet
• Low clouds - have bases below 7,000 feet
• Fog - cloud in contact with the ground
• Multi-level clouds... vertically thick spanning
  multiple layers
• Miscellaneous clouds Example orographic clouds
  - distinct clouds that form via interaction
  between wind and mountainous terrain features

5
(No Transcript)
6
High Level CloudsHigh-level clouds form above
18,000 feet (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, but can appear in a
magnificent array of colors when the sun is low
on the horizon.
7
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.
8
Cirrocumulus Ice clouds. Precipitation possible
within 15 to 20 hours if wind is steady from NE
to S. Early summer A.M. could mean afternoon
thundershowers. Other winds could bring overcast.
9
Cirrostratus Precipitation possible within 15 to
24 hours if wind is steady from NE E to S.
Prismatic effect of sun or moon through ice
crystals cause halo.
10
Mid-Level Clouds The bases of mid-level clouds
typically appear between 6,500 to 18,000 feet
(2,000 to 6,000 meters). 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.
11
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.
12
Altocumulus Water and ice clouds. Some
precipitation possible within 15 to 20 hours if
wind steady from NE to S. Other winds could bring
overcast sky.
13
Altostratus Precipitation possible within 10 to
20 hours if wind is steady from NE to S. Sun
appears as if behind frosted glass. Other winds
could bring overcast sky.
14
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.
15
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.
16
Stratocumulus The State College Mascot
Low water clouds of dark red color. Precipitation
possible in 12 to 20 hours if winds from NE to S.
Other winds may bring an overcast sky.
Immediate threat of bad weather from a sprinkle
to heavy precipitation. If head of a cold front,
gusty winds or thunder showers.
17
More Stratocumulusdoes this look familiar?
18
Fog can be considered as a low stratus cloud in
contact with the ground. When the fog lifts, it
usually becomes true stratus.
19
Vertically Developed Clouds Probably the most
familiar of the classified clouds is the cumulus
cloud. Generated most commonly through either
thermal convection or frontal lifting, these
clouds can grow to heights in excess of 39,000
feet (12,000 meters), releasing incredible
amounts of energy through the condensation of
water vapor within the cloud itself.
20
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.
21
Fair weather cumulus are fueled by buoyant
bubbles of air, or thermals, that rise upward
from the earth's surface. As they rise, the water
vapor within cools and condenses forming cloud
droplets. Young fair weather cumulus have sharply
defined edges and bases while the edges of older
clouds appear more ragged, an artifact of cloud
erosion. Evaporation along the cloud edges cools
the surrounding air, making it heavier and
producing sinking motion (or subsidence) outside
the cloud.
Wasatch Mountains, Salt Lake City, UT
22
Cumulonimbus Precipitation likely and soon,
coming usually from SW W to N. Distant clouds
often show an anvil-shaped cirroform cap.
23
Above Towering Cu from the side Right High Res
Satellite Image of Cumulonimbus clouds.
24
Very rarely (less than 3 of the time) t-storm
produces tornado
Above Various Tornadoes from NOAA website Left
and Right Not really a good Idea.
25
Mammatus" clouds because they resemble the
mammary glands of mammals. They indicate that the
atmosphere is quite unstable and can also be an
indicator of impending severe weather.
26
Other Random Clouds 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.
27
Lenticular clouds are lens-shaped clouds that can
result from strong wind flow over rugged terrain.
At the time of this photo, the winds were blowing
around 30-40 mph from right to left, forming
several lenticular clouds. Sometimes they stack
up like pancakes in multiple layers
28
Another type of 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.
These clouds are called "contrails" (short for
"condensation trails") and look like lines in the
sky.