Download 24.2 Clouds and Fog

24.2 Clouds and Fog
OBJECTIVES
•
List conditions that must exist for clouds to form
•
Identify Types of Clouds
•
Describe ways that fog may form
24.2 Clouds and Fog
•
Clouds are a result of the condensation of water
vapor throughout a large volume of air.
•
Which atmospheric layer are most clouds formed in?
24.2 Clouds and Fog
•
Clouds need a
surface to form on.
•
These surfaces
include tiny
particles of dust
and ice, called
condensation
nuclei.
F/A 18 forces condensation out of the air approaching the speed of sound
24.2 Clouds and Fog
•
For clouds to form, the air must be saturated with
water vapor.
•
As the air gets cooler, it takes less water vapor to
saturate the air.
•
There are usually more clouds on cooler days.
24.2 Clouds and Fog
•
Convective cooling is the
vertical circulation of air that
occurs when air gets heated
from below, by either the
ground or ocean water, that
has been heated by the sun.
•
Convection is a possible cause
of winds. It causes a cooling
of the air.
24.2 Clouds and Fog
• Changes in temperature
that result directly from
the expansion or
compression of air are
called adiabatic
temperature changes.
24.2 Clouds and Fog
•
The base or bottom of a cloud is found at a
level called the condensation level because
it is the level where the temperature change
required for cloud formation ends.
24.2 Clouds and Fog
•
•
Clouds usually surround areas of high
elevation such as mountains because these
objects force warm air upward.
This temperature change causes cloud
formation.
24.2 Clouds and Fog
•
•
Advective cooling is another way clouds
can form.
This is a process in which warm winds blow
across cold oceans or cold areas of land.
24.2 Clouds and Fog
• Clouds are high fogs, mist, or haze that form when air
above Earth’s surface cools below its dew point.
• Three main cloud types:
– Cirrus: thin feathery or tufted high ice-crystal clouds
– Stratus: low sheets or layers, form in stable air
(moving upward slowly)
– Cumulus: thick fleecy masses formed by vertically
rising air currents
Types of Clouds
• Clouds are classified into a system that uses Latin
words to describe the appearance of clouds as seen
by an observer on the ground.
• Latin Root
cumulus
stratus
cirrus
nimbus
alto
Translation
heap
layer
curl of hair
rain
mid-level
Example
cumulus
altostratus
cirrus
cumulonimbus
altocumulus
Types of Clouds
24.2 Clouds and Fog
•
Stratus clouds are sheet like or layered
clouds found close to the earth’s
surface.
Stratus Clouds
Altostratus Clouds
This is an image of altostratus clouds. Notice the difference in thickness
and color in the clouds.
Image courtesy of Keith G. Diem
Stratus Clouds
This image of stratus clouds was taken at sunrise in eastern
Colorado. Stratus clouds usually cover the entire sky.
Image courtesy of Gregory Thompson
24.2 Clouds and Fog
• The term nimbo or nimbus means rain
or snow, as in nimbostratus.
• The term can be attributed to any type
of cloud.
Nimbostratus Clouds
This image of nimbostratus clouds was taken in Seattle, WA. Notice the
rain falling out of the clouds, as well as the rainbow!
Image courtesy of Peggy LeMone
24.2 Clouds and Fog
•
Cumulus clouds are piled or heaped and are
high topped clouds found at varying
elevations.
Cumulus Clouds
Cumulus clouds are puffy white or light gray clouds that look like floating
cotton balls. They have sharp outlines and a flat base.
Image courtesy of Carlye Calvin
Cumulus Clouds
•
Cumulonimbus clouds are clouds that are
most commonly associated with rain.
Cumulonimbus Clouds
This cumulonimbus cloud is well-developed and shows the characteristic
anvil-shape.
Image courtesy of Roberta Johnson
Cumulonimbus
Clouds
24.2 Clouds and Fog
•
Cirrus clouds are curly clouds that are found
at altitudes above 6,000 meters.
Cirrus Clouds
Cirrus clouds are composed entirely of ice and consist of long, thin, wispy
streamers. They are commonly known as "mare's tails" because of their
appearance.
Image courtesy of Lisa Gardiner
Cirrus Clouds
Cirrus Clouds
24.2 Clouds and Fog
•
•
Fog is a result of the condensation of water vapor
in the air.
The temperature difference in the air and on the
ground causes water vapor to condense and form
fog.
Fog