1. Clouds and Precipitation
Alyssa Goodwin

2. Adiabatic Temperature Changes and
Expansion and cooling
• When air is allowed to expand, it cools, and
when it’s compressed, it warms.
• Temperature changes that happen even
though heat isn’t added or subtracted. It’s the
result of compressed air.
• Expansion and cooling happens
because there are fewer and
fewer gas molecules.
http://apollo.lsc.vsc.edu/~wintelsw/MET1010LOL/chapter06/

3. Orographic Lifting
• When elevated terrains act as barriers to air
flow.
• As air goes up a mountain slop, adiabatic
cooling generates clouds and precipitation.
• By the time air reaches the leeward
side of a mountain, much of it’s
moisture has been lost.
https://fp.auburn.edu/fire/weather_elements.htm

4. Frontal Wedging
• Warm and cold air collides
• Cool, dense air act like a barrier then the
warmer, less dense air rises.
• Usually creates rain
https://fp.auburn.edu/fire/weather_elements.htm

5. Convergence
• When air in the lower atmosphere flows
together.
• Air goes up because it cant go down.
• This leads to cloud formation.
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter6/lift_converge.html

6. Localized Convective Lifting
• Unequal heating of the Earth’s Surface
• The air above a warmer, dense area will rise
• When warm parcels of air rise above
condensation level, clouds form.
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/dvlp/cnvrg.rxml

7. Stability
(Density Differences and Stability and
weather)
• Stable air remains in it’s original position,
unstable air rises.
• Stable air resists upward movement.
• Clouds won’t form when stable air resists
upward movement.
http://www.santabarbara.com/community/weather/

8. Condensation
• For any of these forms of condensation to
occur, the air must be saturated.
• It happens when water vapor changes to a
liquid.
• Saturation occurs mostly
when air is cooled to its
dew point or when water
vapor is added to the air.
http://shoalwater.nsw.gov.au/Education/condensation.htm

9. Types of Clouds
• Clouds are classified by their form and height.
• Cirrus-curl of hair, Cumulus-a pile, stratus-a
layer.
• All other clouds reflect one of these three
basic form or are combinations or
modifications of them.
http://eo.ucar.edu/webweather/cloud3.html

10. High Clouds
• Cirrus, Cirrostratus and Cirrocumulus.
• High clouds are thin and white and often
made up of ice crystals
• Low temperatures and small quantities of
water vapor are present at high altitudes.
https://www.meted.ucar.edu/sign_in.php?go_back_to=http%253A%252F%252Fwww.meted.uca
r.edu%252Ffire%252Fs290%252Funit6%252Fprint_2.htm

11. Middle Clouds
• Clouds in the middle range have the prefix
alto- as part of their name.
• Altocumulus clouds are larger and denser that
Cirrocumulus (high Cloud)
• Middle clouds usually are accompanied by
snow or drizzle
https://www.meted.ucar.edu/sign_in.php?go_back_to=http%253A%252F%252Fwww.meted.uca
r.edu%252Ffire%252Fs290%252Funit6%252Fprint_2.htm

12. Low Clouds
• Stratus, Stratocumulus, nimbostratus.
• Look like fog-like layers and have vertical
development.
• Develop in stable air, because air is forced
upward.
https://www.meted.ucar.edu/sign_in.php?go_back_to=http%253A%252F%252Fwww.meted.uca
r.edu%252Ffire%252Fs290%252Funit6%252Fprint_2.htm

13. Clouds of Vertical Development
• Some clouds aren’t categorized by high,
middle, or low, they extend upward.
• Once upward movement is started,
acceleration is powerful and clouds with a lot
of vertical range form.
• End result is cumulonimbus clouds and rain or
thunderstorms.
http://en.wikipedia.org/wiki/Cloud

14. Fog
(by cooling and by evaporating)
• Fog is defined as a cloud with its base at or
very near the ground.
• Form on cool, clear, calm nights when the
surface is cooled rapidly by radiation.
• Cool air moves over warm water, moisture
might evaporate from the water surface to
produce saturation.
http://www.kidsgeo.com/geography-for-kids/0110-fog.php

15. Cold Cloud Precipitation
(Bergeron Process)
• Supercooling and supersaturation.
• Supercooled air will freeze when it impacts a
solid object.
• Ice crystals can’t coexist with water droplets in
air because the air “appears” supersaturated
to the ice.
http://www.geo.hunter.cuny.edu/~tbw/wc.notes/5.cond.precip/precipitation/bergeron_process.htm

16. Warm Cloud Precipitation
(Collision-coalescence process)
• Collision-coalescence process is a mechanism
that forms raindrops.
• As large droplets move through the cloud,
they join with smaller, slower droplets.
• The droplet become bigger from joining.
https://www.meted.ucar.edu/sign_in.php?go_back_to=http%253A%2
52F%252Fwww.meted.ucar.edu%252Fhydro%252Fbasic_int%252Fflas
h_flood%252Fnavmenu.php%253Ftab%253D1%2526page%253D2.2.2

17. Rain and Snow
• Rain means drops of water that fall from a
cloud and have a diameter of at least .5 mm.
• Surface temperature above 4°C, flakes melt.
• At low temperatures, light and fluffy snow
falls.
http://zahiym5tlc.edublogs.org/

18. Sleet, Glaze, and Hail
• Sleet-the fall of small particles of clear-to-
translucent ice.
• Glaze-known as freezing rain
• Hail-produced in cumulonimbus clouds. They
begin as small ice pellets that grow by
collecting supercooled water droplets.
http://www.kidsgeo.com/geography-for-kids/0119-hail.php