INSOLATION

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INSOLATION

• Incoming Solar Radiation
• Electromagnetic energy from the sun that reaches
  Earth
• (do NOT confuse this with insulation)

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Long waves
Short waves
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Insolation

• may be absorbed in the atmosphere.
• Most ultraviolet radiation (UV) is absorbed by
  OZONE in the upper atmosphere
• Ozone O3

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Ozone Holes

• in the upper atmosphere are caused by man-made
  gases called chlorofluorocarbons (CFCs)
• Where there are ozone holes, the UV light is not
  absorbed, and can damage living things on the
  earth below

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Insolation

• may be reflected in the atmosphere.
• CLOUDS can reflect a lot of solar energy back
  into space
• AEROSOLS (small suspended particles) like dust,
  volcanic ash, pollution etc. also reflect solar
  energy

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Factors affecting Insolation

• 1) Surface Characteristics
• Rough texture absorbs more
• Smooth surfaces absorb less
• Dark colors absorb more
• Light colors absorb less

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Factors affecting Insolation

• 2) Change of State
• If insolation is used to melt ice into water
• or evaporate liquid water into water vapor, less
  of the energy is available to raise temperatures

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Factors affecting Insolation

• 3) Angle of incidence of the rays
• The higher the sun is in the sky, the more
  insolation is absorbed on Earth.
• At what time of day is the sun highest?
• At what time of year is the sun highest?
• Where on earth is the sun highest?

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What is the hottest day of the year?

• June1
• June 21
• July 1
• July 21
• August 21

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What day of the year does the northern hemisphere
receive the most insolation from the sun?

• June 1
• June 21
• July 21
• August21

This difference in dates Is called a temperature
lag

Why do these 2 dates differ? hottest day
July21 most insolation June 21
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June 21
The 4 suns shown represent the suns average
height for that season
Dec. 21
July 21
So there is about a 1 month temperature lag in
summer and winter
Jan 21
After Jan.21st temperatures begin to slowly rise.
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Can you explain then why Dec. 21st is not the
coldest day of the year, even though the northern
hemisphere receives the least energy from the sun
on this date?
Think of energy Income as water flowing Into a
bathtub
Think of energy loss as the water going down
the drain. The height of the water in the tub at
any moment is like the current temperature.
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What time of day is the sun highest in the sky?
So this is the most efficient heating time of the
day

• 10 am
• Local solar noon
• 3pm
• 9pm

Is this also the time of day when the
highest temperature occurs? Highest daily
temperature occurs around what time?
1. 10 am 2. Local solar noon 3. 3pm 4. 9pm

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Using the same reasoning as with the date of the
year, explain why the warmest time of day usually
is around 3 or 4 in the afternoon and not 12 noon.
What is the coldest time of day? (this is a bit
different)
Explain your answer
Now lets look at the earth as a whole
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The resulting temperature for any location on
earth is A result of 2 factors
1. Energy income from the sun
2. Energy loss to space
On June 21st the northern hemisphere has the
highest energy income and a constant energy loss
to space
However, for about 1 month after June 21st, the
northern hemisphere is still receiving more
energy from the sun than it is losing. After
late July the northern hemisphere begins to
slowly lose more energy than it receives
and temperatures begin to fall.
Temperatures continue to fall until what date?
Jan. 21st
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What heats up faster, land or water?
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What heats up faster, land or water?

• Land heats up faster because.
• insolation only penetrates a few centimeters in
  soil, but up to 300 meters in water

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What heats up faster, land or water?

• Land heats up faster because.
• water has a much higher specific heat than
  rocks or soil.
• Remember specific heat is how much energy it
  takes to heat one gram by one degree Celsius

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What heats up faster, land or water?

• Land heats up faster because.
• water can flow freely, so convection currents
  distribute the heat throughout a large volume of
  water

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What heats up faster, land or water?

• Land heats up faster because.
• when heated, some of the water evaporates.
  Since some energy is used for this change is
  state, less is available to actually heat the
  water up.

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Energy Balance

• If ..
• Incoming solar radiation outgoing Earths
  radiation
• then.. the Earth gains as much heat as it loses
  and the temperature on Earth remains relatively
  constant

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When the temperature of the earth remains the
same from year to year we say the Earth is in
Radiative Balance
(Radiative Balance means energy received
energy lost)
In the very short term from year to year the
earth is not in radiative balance, example-
Earth can experience a particularly cold winter
in a certain year.
Usually over several decades the earth is in
Radiative balance
Over hundreds, thousands or millions of years the
earth Is not in radiative balance, an example
would be the ice ages.
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Radiative Balance
Energy in
Energy out