MET 112 Global Climate Change - Lecture 3
Clouds and global climate
Dr. Eugene Cordero
San Jose State University
Outline





Water in the earth system
Clouds and the radiation budget
Seasons and energy balance
Atmospheric circulation
Climate Game
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MET 112 Global Climate Change
Questions
 What role do clouds play on the Earth’s
climate?
 What would happen to our climate if clouds
were to increase/decrease?
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Water in the atmosphere
 Definitions:
– Evaporation: Process where a liquid changes into a gas
– Condensation: Process where a gas changes into a liquid
– Precipitation: Any liquid or solid water that
falls from the atmosphere to the
ground. (i.e. RAIN!)
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Water freely
evaporating and
condensing
Since more water
molecules are
evaporating than
condensing, then net
evaporation is
occurring.
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Lid on:
The humidity is now
100%
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Lid on:
Now, evaporation and
condensation are equal.
The air above water is
now called ‘saturated’.
The humidity is now
100%
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Condensation

The process by which water vapor changes to a
cloud droplet

Water vapor molecules may ‘stick’ to
condensation nuclei and grow (billions) to
eventually form cloud droplet.

Examples of condensation nuclei include:
a. Dust
b. Salt
c. Smoke
 Condensation occurs primarily as temperature cools:
-colder the molecules more likely they are to ‘stick’ to
other molecules
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http://www.ssec.wisc.edu/data/comp/cmoll/cmoll.html
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Clouds and radiation
Cloud - Climate Interactions
Albedo effect - COOLING
 Clouds reflect incoming solar radiation.
 The cloud droplet size and total water content
determine the overall reflectivity.
Greenhouse effect - WARMING
 Clouds are good absorbers (and emitters) of long
wave (infrared) radiation.
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MET 112 Global Climate Change
Clouds and day to day
temperatures
Imagine that you are going camping in the Sierras
with your friends. On the first day (and evening) it
is cloudy, while on the second day (and evening) it
is clear. Based on this information alone:
Which day would be warmer?
Which evening would be warmer?
Explain your answers.
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MET 112 Global Climate Change
Which day would be warmer?
1. First day (clear)
2. Second day (cloudy)
3. Both the same
y)
th
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B
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co
n
Se
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0%
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Which evening would be warmer?
1. First day (clear)
2. Second day (cloudy)
3. Both the same
y)
th
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B
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da
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co
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Se
MET 112 Global Climate Change
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19
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Low and High clouds
Consider two types of clouds:
1. Low levels clouds
2. High levels clouds
Q: How is the Earth’s surface energy budget
different for low clouds compared to high
clouds?
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MET 112 Global Climate Change
Clouds and climate
Cloud A: Low level, (dark, thick)
Excellent reflector of incoming radiation;
good absorber/emitter of infrared radiation
Cloud B: High level, light
(sub visible or thin)
Fair/poor reflector of incoming radiation;
good/excellent absorber/emitter of
infrared radiation
 So, clouds both warm and cool the earth.
 Overall, though, clouds act to cool the
earth
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Changes in clouds
 Increases in low level clouds will:
–
 Increases in high level clouds will:
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MET 112 Global Climate Change
Changes in clouds
 Increases in low level clouds will:
– cool the surface (cooling outweighs
warming)
 Increases in high level clouds will:
– warm the surface (warming outweighs
cooling)
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Explain how the earth’s climate would
change as a result of aircarft contrails.
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Questions
1. What percentage of the sun’s radiation is
a) absorbed by the Earth’s surface?
b) absorbed by the atmosphere
c) reflected out to space?
2. What percentage of the energy received by the earth’s surface
comes directly from greenhouse gas emissions?
3. If the sun’s radiation was to increase by 10%, how would the
following energy units change (increase, decrease or stay the
same)
a) Energy gained by the Earth’s surface.
b) Energy lost by the Earth’s surface.
c) Energy emitted by greenhouse gases.
d) Energy lost to space.
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MET 112 Global Climate Change
What percentage of the Sun’s radiation
is absorbed by the Earth’s surface?
19%
51%
70%
117%
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0%
0%
1.
17
0%
0.
7
0 of 70
0.
19
0%
0.
51
1.
2.
3.
4.
37
What percentage of the Sun’s radiation
is absorbed by the Earth’s atmosphere?
19%
51%
70%
117%
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0%
0%
1.
17
0%
0.
7
0 of 70
0.
19
0%
0.
51
1.
2.
3.
4.
38
What percentage of the sun’s radiation
is reflected out to space?
19%
30%
64%
70%
111%
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0%
0%
1.
11
0%
0.
7
0%
0.
3
0 of 70
0.
19
0%
0.
64
1.
2.
3.
4.
5.
39
What percentage of the energy gained
by the earth’s surface comes directly
from greenhouse gas emissions?
30%
43%
51%
65%
70%
MET 112 Global Climate Change
0%
0%
0.
7
0%
0.
65
0%
0.
43
0 of 70
0.
3
0%
0.
51
1.
2.
3.
4.
5.
40
If the Sun’s radiation was to increase by
10%, how would the energy gained by
the earth’s surface change?
1. Increase
2. Decrease
3. Stay the same
sa
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41
If the Sun’s radiation was to increase by
10%, how would the energy emitted by
greenhouse gases change?
1. Increase
2. Decrease
3. Stay the same
sa
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If the Sun’s radiation was to increase by
10% the energy
MET 112 Global Climate Change
..
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1. Entering the top of the
atmosphere would
exceed the energy
leaving
2. Entering the top of the
atmosphere would be
less than leaving
3. Entering and leaving
would be the same
43
Controls on Climate
Definitions
 Insolation – Incoming solar radiation
 Solstice – day of the year when the sun shines
directly over 23.5°S or 23.5°N
 Equinox –
days of the year when the sun shines
directly over the equator
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Sun angle
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Sun angle (2)
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What influences incoming solar
energy?
 The Sun’s angle of incidence:
– Lower sun angle, less incoming energy
– Higher sun angle, more incoming energy
 Length of time the Sun shines each day:
– Summer season, more sun hours
– Winter season, less sun hours
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Why do we have seasons?
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What month do you think this graph represents?
a) December b) March c) June d) September
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What month do you think this graph represents?
December
March
June
September
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Review questions
 On June 21st, at what latitude is the sun directly
overhead at noon?
 On September 22nd, at what latitude is the sun
directly overhead at noon?
 How many hours of daylight are present at the
South Pole on February 20th?
 Where would you expect to have longer days;
45 ° N on June 21st or 50°S on Dec 21st?
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MET 112 Global Climate Change
On June 21st, at what latitude is the sun
directly overhead at noon?
Equator (0)
23.5°N
23.5°S
90°N (north pole)
90°S (south pole)
0%
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po
(s
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90
°S
(n
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90
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0%
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.5
°S
.5
°N
0%
°N
0 of 70
0%
23
Eq
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to
r
(0
)
0%
23
1.
2.
3.
4.
5.
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How many hours of daylight are present
at the South Pole on February 20th?
0 hours
6 hours
12 hours
18 hours
24 hours
MET 112 Global Climate Change
ho
24
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18
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0%
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0%
12
1.
2.
3.
4.
5.
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On September 22nd, at what latitude is
the sun directly overhead at noon?
Equator (0)
23.5°N
23.5°S
90°N (north pole)
90°S (south pole)
0%
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(s
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MET 112 Global Climate Change
0%
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0%
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0 of 70
0%
23
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1.
2.
3.
4.
5.
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Where would you expect to have longer days;
45 ° N on June 21st or 50°S on Dec 21st?
45°N
50°S
They are the same
Impossible to tell
ce
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63
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Controls on Climate
 Seasonal temperature and precipitation patters
are generally attributable to:






Latitude
Mountains and highlands
Land and water location
Prevailing winds
Pressure and wind systems
Ocean currents
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MET 112 Global Climate Change
Annual Surface Temperature
Questions
 Indicate the warmest and coldest areas of the
Earth.
 Consider the temperature at 60N latitude.
Indicate on the map the coldest and warmest
places at 60N.
 What is the temperature difference between
these locations
 What factors might explain this temperature
difference?
 Why is there not a similar difference seen at 60S?
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MET 112 Global Climate Change
Annual Surface Temperature
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Climate controls:
Latitude/Mountains
 Latitude
– Higher latitude climates are generally
(cooler/warmer)
– Lower latitudes climates are generally
(cooler/warmer)
 Mountains
– Higher altitudes climate are generally
(cooler/warmer): cooler temperatures
– Windward side of mountains are generally
(cooler/warmer) and (wetter/drier), than
leeward side
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Climate controls:
Latitude/Mountains
 Latitude
– Higher latitude climates are generally
(cooler/warmer)
– Lower latitudes climates are generally
(cooler/warmer)
 Mountains
– Higher altitudes climate are generally
(cooler/warmer): cooler temperatures
– Windward side of mountains are generally
(cooler/warmer) and (wetter/drier), than
leeward side
MET 112 Global Climate Change
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Controls on Climate
 Seasonal temperature and precipitation patters
are generally attributable to:






Latitude
Mountains and highlands
Land and water location
Prevailing winds
Pressure and wind systems
Ocean currents
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Controls on Climate: Oceans
 Ocean Temperatures
– Coasts of continents are affected by ocean
temperatures: Generally less temperature
extremes compared to interior of continents
– Cold oceans:
generally produce cooler/drier conditions
– Warm oceans:
generally produce more warm/humid conditions
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Cold ocean
Warm ocean
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Dry
Humid
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Controls on Climate: Pressure
systems
 Rising and sinking motion associated with low
and high pressure affects climate
 Areas where pressure seasonally low,
–
Tropics: rainy
 Areas where pressure seasonally high,
– Subtropical high (30N/3OS): warm and dry
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January Average sea-level Pressure and surface wind pattern
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July Average sea-level Pressure and surface wind pattern
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Climate Game
Names ___________________________
 Match the city with the corresponding climatology
by indicating the appropriate letter







Sacramento, California (38°N)
Phoenix, Arizona (33°N)
Denver, Colorado (40°N)
Iquitos, Peru (4°S)
Mobile, Alabama (30°N)
Winnipeg, Canada (50°N)
Fairbanks, Alaska (65°N)
_____________
_____________
_____________
_____________
_____________
_____________
_____________
City A
Sacramento, California
Phoenix, Arizona
Denver, Colorado
Iquitos, Peru
Mobile, Alabama
Winnipeg, Canada
Fairbanks, Alaska
43%
20%
14%
11%
9%
3%
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MET 112 Global Climate Change
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City B
Sacramento, California
Phoenix, Arizona
Denver, Colorado
Iquitos, Peru
Mobile, Alabama
Winnipeg, Canada
Fairbanks, Alaska
82%
5%
8%
3%
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MET 112 Global Climate Change
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City C
Sacramento, California
Phoenix, Arizona
Denver, Colorado
Iquitos, Peru
Mobile, Alabama
Winnipeg, Canada
Fairbanks, Alaska
70%
11%
3%
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91
City D
Sacramento, California
Phoenix, Arizona
Denver, Colorado
Iquitos, Peru
Mobile, Alabama
Winnipeg, Canada
Fairbanks, Alaska
87%
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MET 112 Global Climate Change
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City E
Sacramento, California
Phoenix, Arizona
Denver, Colorado
Iquitos, Peru
Mobile, Alabama
Winnipeg, Canada
Fairbanks, Alaska
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16% 16%
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93
City F
Sacramento, California
Phoenix, Arizona
Denver, Colorado
Iquitos, Peru
Mobile, Alabama
Winnipeg, Canada
Fairbanks, Alaska
61%
26%
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