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1. INSOLATION
Sun is the main source of energy for Earth. Radiation of solar
ray is main source of energy for Atmosphere.
Diameter of sun – 1382400 kms (109 times more than earth)
Velocity of electro magnetic short waves – 297600 km/ second
Time to reach earth – 8 min 20 sec
Mass – 332000 times that of earth
Average density – 1.41 earth – 5.52
Surface temperature – 5500 to 6100 oC
Energy coming to earth – 1/ 2 billionth equal to 23 billion HP
Solar constant – 1.94 gram cal / sq. cm. / minute
There Hydrogen is changed in to Helium through nuclear fusion.
Electro magnetic waves – 1. longer – Infrared waves
2. shorter - U.V. rays

2. ELECTROMAGNATIC SPECTRUM
The solar energy radiated from the sun in the form
of electromagnetic wave is called electro
magnetic radiation.
The energy from the sun or electromagnetic
radiation waves are expressed in terms of
wavelength (L).
The number of radiation wave passing through a
certain point per unit time (one second) is called
wave frequency.
Wave frequency is generally expressed as wave
cycle per second, expressed in hertz,
kilohertz(1000 hertz), megahertz(1000,000 hertz)

3. • INcoming SOLar radiATION
• The part of the sun’s radiation that is
received by Earth.

5. 1. The first spectrum – include GAMA RAYS, HARD X
RAYS, SOFT X RAYS, ULTRAVIOLET RAYS. The
wave length unit of measure in terms “ angstrom” 1
angstrom = 0.00000001 cm
2. The second spectrum – the spectrum of visible light
which include violet, blue, green, yellow, orange
and red rays. Which carry 41 % of the total energy
of the solar spectrum. Micron is the unit measure. 1
micron = 0.0001 cm
3. The third spectrum – is called as infrared spectrum.
Wave length ranging from 0.7 to 300 microns.
4. The fourth spectrum - consists of long waves
including microwaves and radar waves -- radio
system & television system .

6. Diagram

7. Factors affecting Insolation
1. Angle of sun’s rays - Angle of incidence – the
angle at which the insolation strikes earth’s surface
• Altitude of sun determines the angle of incidence.
• The higher the sun is in the sky, the higher the angle
of incidence and more insolation is absorbed.
• A lower angle of incidence more insolation is
reflected and less is absorbed.
equator pole

8. Earth's atmosphere reduces the amount of
insolation striking earth's surface.
Earth's atmosphere and tilt combine to explain
variation in received solar radiation.

10. 2. Length of day and night
• Duration of insolation: The number of daylight
hours at a given location. This varies with latitude
and season.
• The longer the earth receives light the more
insolation it gets.
• If I hold a lamp at a great distance from an ice cube,
for a long time will the ice cube eventually melt?
• The longer the day, the more insolation reaches the
earth.
• This is a Direct relation ship.

11. DAY and NIGHT LENGTH
Antarctic circle 66.5°S
Arctic circle 66.5°N
North Pole 90°N
South Pole 90°N
Equator 0°
Tropic of Cancer
23.5°N
Tropic of Capricorn
23.5°N
Six months daytime (March-Sept), six
months night (Sept - March)
Six months daytime (Sept - March),
six months night (March-Sept)
One day with 24 hours daylight
(June 21st); one day with 24 hours
darkness (Dec 21st)
One day with 24 hours daylight
(March 21st); one day with 24
hours darkness (June 21st)
Sun is overhead once a year
(June 21st). Day length always
at least 10 hours.
Sun is overhead once a year
(Dec 21st). Day length always at
least 10 hours.
Constant day length - 12 hours day
and night all year round
Lengths of day and night
vary more between the
seasons at higher
latitudes. This makes
climate more seasonal at
the poles than the
equator
More
seasonal
More
seasonal

12. Earth's surface is 5 million kilometers further from
the sun in summer than in winter, indicating that
seasonal warmth is controlled by more than solar
proximity.
3. Distance between earth and sun
PERIHELION APHELION

13. 4.Sunspots or Solar constant
Created on outer surface of sun due to periodic
disturbances and explosions on the solar surface. It is
observe that appearing large number of sunspots the
intensity of the solar radiation received is larger at earth
surface.
Haley in 1710 – study 22 years of sunspots- cycle of 11
years the number of sunspots increases or decreases

14. 5. Transparency of the atmosphere –
reflection from dust particals, salt particals and
smoke particals reflecting short wave solar
radiation to space.
reflection from the cloud tops also deflects the
amount of solar radiation that would be
otherwise available to earth.
transparency also related to latitude –
• Oblique rays
• Vertical rays

15. Latitudinal and Seasonal variation / distribution
• Amount of insolation received by earth decreases towards pole.
• Temporal variation at different latitudes at diff times of a year.
• BAUR & PHILLIPS – solar radiation reaching at outer limit of
atmosphere is more than the amount received at earth surface.
• But this is the fact that greater portion of insolation is lost while
passing through the atmosphere due to the effect of scattering,
reflection, absorption, cloudiness.
• SUMMER SOLSTICE – (21 June)- maximum insolation reaches at
outer limit of atmosphere at North pole. But maximum energy
received at the ground surface at 30 to 40 latitude. Because of
minimum amount of cloudiness due to presence of subtropical high
pressure belt and anticyclone conditions. But at pole the insolation
become so low that they received about 40 % of the amount
received by the Equator.

16. The summer solstice
occurs when the
Northern Hemisphere
is tipped towards the
sun. The winter
solstice occurs when
the Northern
Hemisphere is tipped
away from the sun.

17. The globe is divided in to three zones on the basic of
amount of insolation received during the course of year
Equatorial: intense insolation, day and night roughly equal
Tropical: high annual insolation, marked seasonal cycle
Subtropical: large annual insolation; strong seasonal cycle
Mid latitude: strong seasonal contrasts in insolation and length of
day
Arctic/subarctic, Antarctic/ subantarctic: enormous variation in
annual insolation, extreme variation in day length
Polar: greatest seasonal insolation contrasts, 6-month day, 6-
month night

20. EFFECT OF ATMOSPHERE ON INSOLATION
The electro magnetic solar radiation or incoming
short wave solar radiation has to pass through thick
layer of atmosphere, hence it is partly absorbed,
scattered, and reflected.

21. ABSORPTION
• The energy radiated from the sun towards earth.
• It is 1/ 2 billion part reaches the earth.
• If it is consider 100% then 14% of energy is absorped
by atmospheric gases and water vapor.
• Ozone is on large extent, O2, CO2 are very limited
extent, nitrogen on poor absorber of insolation.
• Process of absorbtion is selective in nature.
• O2,O3 – absorb shortest wave length 0.02 to0.29
micron
• Ozone – U. V. rays wave length of 1000 to 4000
angstrom
• Water vapor – wave length of 0.9 to 2.1 micron
• The energy absorb transmitted in to internal molecular
motion which causes a rise in temperature.

22. SCATTERING
• 23 % of insolation scattered in atmosphere by dust
particals and Haze.
• 6 % sent back to atmosphere
• 17 % reaches to earth.
• Process of scattering is selective one.
• When the diameter of dust particals and molecules
of atmospheric gases is shorter than the wave
length of the solar radiation waves.
• Blue light is more scattered than red light.
• Due to scattering effect sky appear blue and at the
time of sunrise & sunset sky appears reddish.

26. DIFFUSION
• Diameter of the particals are larger than the
wavelength, true scattering dose not possible
and the effect of diffusion occur.
• it is effective for all wave length.
• non selective in nature.
• Eg – light reflected from clouds is pure white.
• the twilight are longer duration in high latitudes
due to diffusion.

27. REFLECTION
• 27 % radiation reflected back is called as reflection
of light.
• It does not play any roll for heating the atmosphere.
• Diameter of dust particals and molecule of water
vapor is longer than wave length of incoming solar
radiation reflection takes place.
• Some energy remains in lower atmosphere.

29. ALBIDO
• The portion of incident radiation energy reflected
back from the earth surface is called Albido.
• Various data received so far indicate the Earths
average albido varying between 29 % to 34 %.
Fresh snow – 80 – 85 % Forest 5 – 10 %
Old snow 50 – 60 % water (sun near horizon) 50 – 80 %
Sand 20 – 30 % Thick cloud 70 – 80 %
Grass 20 – 25 % Thin cloud 25 – 50 %
Dry earth -15 – 25 % Wet earth 10 %

30. HEAT BUDJET AND HEAT BALANCE