2. Adiabatic Temperature Changes
and Expansion and Cooling
• The slower rate of cooling
caused by the addition of
latent heat is called the wet
adiabatic rate, and the rate of
cooling or heating applies to
unsaturated air and is called
the dry adiabatic rate.
• When air is allowed to
expand, it cools, and when it
is compressed, it warms.
• The amount of latent heat
http://apollo.lsc.vsc.edu/classes/met130/n
otes/chapter6/adiab_cool.html released depends on the
quantity of moisture present
in the air.
3. Orographic Lifting
• When elevated terrains,
such as mountains, act as
barriers to air flow,
orographic lifting occurs.
• By the time air reaches
the leeward side of a
mountain, much of its
moisture has been lost.
• Many of the rainiest
places on Earth are
located on these
windward mountain
https://earthscience-in-the- slopes.
nationalparks.wikispaces.com/Death+Valley
4. Frontal Wedging
• In central North
America, masses of
warm air and cold air
collide, producing a
front.
• Weather-producing
fronts are associated
with specific storm
system called middle-
latitude cyclones.
• The cooler, denser air
acts as a barrier over
which the warmer, less http://www.harding.edu/lmurray/113_files/HT
dense air rises. ML/d2_Earth%20Revised/sld046.htm
5. Convergence
• Convergence can cause
cloud development and
precipitation.
• The pattern of air
movement and the
uplift that results is
helped along by intense
solar heating of the
land.
• Convergence is
whenever air in the
lower atmosphere
flows together, lifting https://commons.wikimedia.org/wiki/File:Oce
results. anic-
continental_convergence_Fig21oceancont_itali
an.svg
6. Localized Convective Lifting
• Unequal heating of
Earth’s surface may
cause pockets o air to
be warmed more then
surrounding air.
• Rising parcels of
warmer air are called
thermals.
• Birds, such as hawks
and eagles, use
thermals to carry them
to great heights.
http://www.richhoffmanclass.com/chapter4.ht
ml
7. Stability
• Stable air tends to remain in its
original position, while unstable
air tends to rise
• When air temperature actually
increases with height, it is
called temperature inversion.
(an inversion is created because
the ground and the air
immediately above the ground
will cool more rapidly than air
higher above the ground.
• When stable air is forced above
Earth’s surface, the clouds that
form are widespread and have
little vertical thickness.
http://deved.meted.ucar.edu/marine/mbl/prin
t.htm
8. Condensation
• Condensation happens
when water vapor in
the air changes to a
liquid.
• For any of these forms
of condensation to
occur, the air must be
saturated.
• When condensation
occurs in the air above
the ground, tiny bits of
particulate matter,
called condensation
nuclei, serve as http://www.weatherquestions.com/What_is_c
surfaces for water- ondensation.htm
vapor condensation.
9. Types of Clouds
• Clouds are classified on the basis of their form
and height.
• There are three cloud groups- Cirrus, Cumulus,
and Stratum.
http://eo.ucar.edu/webweath
er/cloud3.html
10. High Clouds
• Three types of clouds make up the high cloud
family- Cirrus, Cirrostratus, and Cirrocumulus.
• All high clouds are thin and white and often
made up of ice crystals.
• High clouds are considered to be precipitation
makers.
http://scienceprep.o
rg/clouds.htm
11. Middle Clouds
• Middle clouds are
clouds that appear
to be middle
range.
• They create a
uniform white to
grayish sheet
covering the sky
with the sun or
moon visible as a
bright spot.
http://www.odu.edu/~tmmathew/geol442/clo • Infrequent light
uds.shtml snow or drizzle
may accompany
these clouds.
12. Low Clouds
• There are three
members of the low
cloud family-
Stratus,
Stratocumulus, and
Nimbostratus.
• These clouds are a
uniform, fog-like
layer that
frequently covers
much of the sky.
• Low clouds are one http://www.scienceinschool.org/print/1940
of the main
precipitation
makers.
13. Clouds of Vertical Development
• Some clouds do
not fit into any of
the three
categories.
• They are all related
to one another and
are associated with
unstable air.
• Cumulus clouds
that are often
connected with fair
weather, may grow
dramatically under
the proper
circumstances.
http://www.richhoffmanclass.com/chapter5.ht
ml
14. Fog
• Fog is defined as a
cloud with its base at or
very near the ground.
• When fog is dense,
visibility may be only a
few dozen meters or
less, making travel
difficult and dangerous.
• When cool air moves
over warm water,
enough moisture may
evaporate from the
water surface to http://www.crh.noaa.gov/jkl/?n=fog_types
produce saturation.
15. Cold Cloud Precipitation
• Water in the
liquid state
below 0 degrees
Celsius is said to
be “super
cooled”.
• The Bergon
process.
• When air is
saturated with
http://www.srh.noaa.gov/lzk/?n=mar2011.ht
respect to water,
m it is super
saturated.
16. Warm Cloud Precipitation
• In warm clouds, the
mechanism that forms
raindrops is the
collision-coalescence
process.
• Much rainfall can be
associated with clouds
located well below
the freezing level.
• Some water-
absorbing particles
can remove water
vapor from the air at
relative humidity's https://www.meted.ucar.edu/sign_in.php?go_
less then 100% back_to=http%253A%252F%252Fwww.meted.
forming droplets that ucar.edu%252Ftropical%252Ftextbook_2nd_ed
ition%252Fnavmenu.php%253Ftab%253D6%2
are quite large. 526page%253D3.0.0
17. Sleet, Glaze, and Hail
• Sleet is the fall of
small particles of
clear-to-translucent
ice.
• Hail is produced by
Cumulonimbus
clouds.
• If the ice pellets
encounter a strong
updraft, they may be
http://www.ksl.com/?nid=367&sid=1150322 carried upward and
begin the downward
journey once more.
