This document discusses various cloud formation processes and types of precipitation. It explains how temperature changes during air expansion and compression can cause clouds to form through processes like orographic lifting and frontal wedging. Different cloud types like cirrus, cumulus and stratus clouds that form at high, middle and low altitudes are described. The document also outlines precipitation processes for warm and cold clouds, and defines types of precipitation including rain, snow, sleet, hail and glaze.

1. Clouds and Precipitation
By: Alaina Klee
http://www.wpclipart.com/weather/rain_water/rain_cloud_BW.png.html

2. Adiabatic Temperature Changes and
Expansion and Cooling
• Temperature changes
that happen even
though heat isn't added
or subtracted
• When air expands it
cools, and when it is
compressed it heats up
• As air moves up into the
atmosphere it expands
and cools
http://www.kidsgeo.com/geography-for-
kids/0070-adiabatic-temperature-changes.php

3. Orographic Lifting
• When elevated land acts
as a barrier to air flow
• As the air goes up,
adiabatic cooling usually
occur and causes clouds
and precipitation
• By the time air gets to the http://www.myoops.org/twocw/usu/Fores
t__Range__and_Wildlife_Sciences/Wildlan
leeward side of a d_Fire_Management_and_Planning/Unit_
mountain , most of the air 7__Atmospheric_Stability_and_Instability_
3.html
moisture is gone.

4. Frontal Wedging
• Warm and Cold air
collide making a front.
• Cooler/denser air is a
wall to warm air, the
warm air rises.
• Another way to lift air
http://www.geography.hunter.cuny.edu/~tbw/
wc.notes/4.moisture.atm.stability/frontal_wed
ging.htm

5. Convergence
• this is where the air that
flows in more than one
direction goes.
• lifting is the result of air in
the lower atmosphere
flowing together. http://www.panoramio.com/photo/195
• Air flow from the ocean 11021
along the coast leads to a
pileup of air and general
convergence over the
peninsula.

6. Localized Convective Lifting
• unequal heating can
cause pockets of air to be
warmed more than the
surrounding air on the
Earth’s surface.
• thermals are the rising
parcels of warmer air. http://wps.prenhall.com/esm_lutgens_fo
undations_4e/47/12104/3098876.cw/co
• humans use these ntent/index.html
thermals for hang gliding
and birds use it to soar
through the sky with
ease.

7. Stability (Density Differences & Stability
and daily weather)
• unstable air tends to rise,
while stable air tends to
remain in its original
position.
• expansion can cause the
volume of air that is
forced to rise, to have a
drop in temperature.
• When stable air resists
vertical movement it
causes unstable air to rise
freely.

8. Condensation
• When water vapor in
the air changes to a
liquid.
• Many times it will either
be in the form of fog,
dew, or clouds.
• This only occurs if air is
http://www.signsoflightstore.net/newgallerym
saturated aker14STORE.php?mytitle=interesting

9. Types of clouds
• Cirrus clouds appear as
patches or as feather-
like wispy fibers.
• Cumulus clouds appear
to look like rising domes
or towers.
• Stratus clouds tend to
look like sheets or layers
that cover most of the
sky.
http://en.wikipedia.org/wiki/File:Clouds.JPG

10. High Clouds
• Cirrus, cirrocumulus, and
cirrostratus make up
these clouds.
• The cirrocumulus clouds
are fluffy, while the
cirrostratus clouds are flat
layers.
• Often made up of ice
crystals because of low
temperatures and small http://www.bigbranch.net/high%20clouds.htm
quantities of water vapor
present at high altitudes

11. Middle Clouds
• These are also known as
altocumulus clouds.
• They also have larger,
denser, rounded masses
compared to
cirrocumulus clouds.
• Are a uniform white to
grayish sheet covering
http://www.bigbranch.net/middle%20clouds.h
the sky with the sun or tm
moon visible as a bright
spot.

12. Low Clouds
• Stratus, stratocumulus,
and nimbostratus are
what make up these
clouds.
• Rarely do these clouds
have precipitation and if
they do it’s a light
amount.
http://patschilling.com/pages/otherlandscapes
• Nimbostratus clouds .html
are the main producers
of precipitation

13. Clouds of Vertical Development
• Clouds that don’t fit into
any of the three height
categories.
• The bases are normally in
the low height range but
can extend upward into
the middle or high
altitudes.
• These are clouds that
grow dramatically under http://thestormking.com/tahoe_nuggets/Nugg
the proper circumstances et_87/nugget_87.html

14. Fog (by cooling and by evaporation)
• Appearance wise, there is
no difference between a
fog and a cloud.
• The only difference
between them is the
method and place of
formation.
• Generally the result of
radiation cooling or the
movement of air over a
cold surface. http://lupusincolor.blogspot.com/2011/01/lup
us-fog.html

15. Cold Cloud Precipitation (Bergeron
process)
• Relies on two physical
processes: supercooling
and supersaturation
• Pure water suspended in
the air isn’t supercooled
until it has reached 0°C
• When the air appears to
be supersaturated to the
http://www.atmo.arizona.edu/students/c
ice crystals, the ice ourselinks/spring07/nats101s2/lecture_n
crystals can’t coexist with otes/mar30.html
water droplets.

16. Warm Cloud Precipitation (collision-
coalescence process)
• Clouds located well below
the freezing level may
have plenty of rainfall.
• The collision-coalescence
process is the mechanism
that forms raindrops in
warm clouds.
• Water vapor can be
removed from the air at
relative humidities less http://claremont327.blogspot.com/2009/11/cl
ouds-and-precipitation.html
than 100 percent with
water-absorbing particles.

17. Rain and Snow
• Rain is drops of water
that fall from a cloud.
• Snowflakes melt and
continue their descent
as rain before they
reach the ground.
• Light, fluffy snow made
up of individual ice
crystals form when http://snowpictures.net/Snow-
storm.html
there are low
temperatures in the air.

18. Sleet, Glaze and Hail
• The fall of small
particles of clear-to-
translucent ice, known
as sleet.
• Freezing rain or the
result of raindrops
http://www.waterencyclopedia.com/Ce-
becoming supercooled, Cr/Climate-Moderator-Water-as-a.html
known as glaze.
• Cumulonimbus clouds
are produced by hail.