Muhammad Fahad Ansari 12IEEM14

1. Radiation Understanding
•Muhammad
Fahad Ansari
12IEEM14

2. 15 Lecture Material for Introduction of
Environmental Physics
Class 12 EE Batch
1. Sound and Light
2. Radiation Understanding
3. Global Warming
4. Terrestrial Environment
5. Extra-Terrestrial Environment
6. Natural and Man made radiation
7. Universe understanding
8. Understanding water
9. Cloud formation
10. Climate
11. Climate change

3. Radiation Understanding
1. EATRH’S ATMOSPHERE
2. STRUCTURE
3. SUN’S ELECTROMAGNETIC SPECTRUM
4. Energy from the Sun
5. Atmospheric Greenhouse Effects

4. Radiation and Earth’s Atmosphere
• The earth’s global average surface temperature in present
climate is 15C (59F). Without the atmosphere, it would be -18C
(-0.4F),
• About 33C or 59.4F colder! Atmosphere is the most important
component of the earth’s climate.
• Radiation vs. other heat sources:
• Total energy enter the earth’s atmosphere: 174 petawatts or
174X1015 Watts
• Solar: 99.978%, Geothermal: 0.013%, waste and fossil fuel:
0.007%, tidal: 0.002%

5. Earth’s Atmosphere
1. What is it?
A thin gaseous envelope around the planet.
Blue sky!
2. Composition
Today’s atmosphere: nitrogen (78%), oxygen
(21%), other (1%) – trace gases!
Nitrogen, oxygen, argon, water vapor, carbon dioxide, methane, and most
other gases are invisible.
Clouds are not gas, but condensed vapor in the form of
liquid droplets or ice particles.
Ground based smog, which is visible, contains reactants of
nitrogen and ozone.
3. Structure Four layers:
Troposphere (overturning) From surface to 8-18 km
Stratosphere (stratified) From troposphere top to 50 km
Mesosphere
Thermosphere

6. The Structure of Earth’s Atmosphere
1. Four layers defined by
temperature
Troposphere: T decreases with elevation
Stratosphere: T increases with elevation
Mesosphere: T decreases with elevation
Thermosphere: T increases with elevation
2. Importance to climate and climate change
Troposphere:
80% of Earth’s gases
Most of Earth’s weather happens
Most of the measurements
Stratosphere:
19.9% of Earth’s gases
Ozone layer:
Blocking Sun’s ultraviolet radiation

7. Energy from the Sun
1. Characteristics
Travels through space (vacuum)
in a speed of light
In the form of waves:
Electromagnetic waves
In stream of particles (Photons)
Releases heat when absorbed
2. Electromagnetic spectrum
From short wavelength, high energy,
gamma rays to long wavelength, low
energy, radio waves
3. Importance to climate and
climate change
Primary driving force of Earth’s climate engine
Ultraviolet, Visible, Infrared

8. Sun’s Electromagnetic Spectrum
Solar radiation has peak intensities in the shorter
wavelengths, dominant in the region we know as visible, thus
shortwave radiation

9. Longwave & Shortwave Radiation
The hot sun
radiates at
shorter
wavelengths
that carry more
energy, and the
fraction
absorbed by the
cooler earth is
then re-radiated
at longer
wavelengths.

10. Atmospheric Greenhouse Effects
T= 15°C
(59°F)
Surface Temperature With the
Atmosphere T= –18°C
(0°F)
Surface Temperature Without the
Atmosphere
Greenhouse effects make Earth’s surface warmer!

12. Greenhouse Gases
 What are they?
Water vapor (H2O)
Carbon dioxide (CO2) Methane (CH4)
Ozone (O3) Chlorofluorocarbons Nitrous oxide (N2O)
(CFC’s)
 Water vapor accounts for 60% of the atmospheric greenhouse effect, CO2 26%,
and the remaining greenhouse gases 14%.
 CO2 contributes most (55-60%) to the anthropogenic greenhouse effect,
and methane is a distant second (16%).
 CFCs cause the strongest greenhouse warming on a molecule-for-molecule
basis.

13. Nitrous
Atmospheric Absorption Oxide
Methane
Solar radiation passes
rather freely through
Earth's atmosphere. Ozone
Absorption
Earth emits longwave
Water Vapor
(100%)
energy, which either
leaks through a narrow
window or Carbon
Dioxide
is absorbed by
UV
greenhouse gases and IR
radiated back to Earth.
Total Atmo
Wavelength

14. Solar Intensity and Latitude
Solar intensity, defined as the energy per area, is different at
different latitude.
A sunlight beam that strikes at an angle is spread across a greater
surface area, and is a less intense heat source than a beam
impinging directly.

15. Unequal Radiation on a Sphere
Insolation is
stronger in the
tropics (low
latitudes) than in
in the polar
regions (high
latitudes).

16. Pole-to-Equator Heating Imbalances

17. What controls the elevation of the Sun above the horizon?
Earth’s Tilt Primarily Determines Season

18. Earth's Annual Energy Balance
The balance is
achieved locally
Incoming Solar
at only two lines
Radiation
of latitude.
A global balance
Outgoing Longwave
is maintained by Radiation
excess heat from
the equatorial
region
transferring
toward the
poles.
Unequal heating of tropics and poles

19. The Global Energy Budget: Driver of Atmospheric Motion
A balance exists between
the incoming solar and
outgoing longwave energy
averaged over the globe
and the year
However, the tilt of the
SURPLUS DEFICIT Earth means this balance
is not maintained for each
latitude

20. Questions:
• What is the current global mean surface temperature?
• Why it is 33C or 59F warmer than it would be without the
atmosphere?
• Why is climate dominated by the radiation balance of the
atmosphere?
• What are the main greenhouse gases in the earth’s
atmosphere?
• In what latitudes the earth’s gain and lost radiative energy
(heat), respectively?

21. Questions:
• What is the current global mean surface temperature?
– 15C or 59F
• Why it is 33C or 59F warmer than it would be without the
atmosphere?
– Because of greenhouse effect of the atmosphere
• Why is climate dominated by the radiation balance of the
atmosphere?
– It contributes to 99.978% of total heat flux into the atmosphere
• What are the main greenhouse gases in the earth’s
atmosphere?
– H2O, CO2, CH4, O3, CFCs, NO2
• In what latitudes the earth’s gain and lost radiative energy
(heat), respectively?
– Gain heat in the tropics or 40S-40N, loss heat in high latitudes
(50S-50N)

22. Interested in more questions? Try these
questions:
• Can you name one or more main causes of glacier
and interglacier climate change?
• What is the most important greenhouse gases for
modern climate change? What is the fastest growing
greenhouse gas?
• Earth’s climate has been much colder and warmer
than that of today. Do you know in what ways the
earth’s radiation balance was altered?