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Solar Radiation

Energy exchanges are derived from Kiehl & Trenberth (1997).

Слайды и текст этой презентации

Слайд 1Solar Radiation
The energy emitted by the Sun is called
SOLAR RADIATION.
It

is the only source of energy for the Earth.
Other sources:

Earth’s surface – 5000 times less,
Stars – 30.000.000 times less.
When arriving to Earth, the larger part of the solar radiation (SR) transforms to heat energy, and a small portion of it to electric energy (upper atmosphere).
area receives annually of energy



Solar Radiation		The energy emitted by the Sun is called		SOLAR RADIATION.		It is the only source of energy for

Слайд 2
Energy exchanges are derived from Kiehl & Trenberth (1997).

Energy exchanges are derived from Kiehl & Trenberth (1997).

Слайд 3Energetic state of a body
Any body the temperature of which

is above 0 K radiates energy.









Equilibrium state

Non-equilibrium state



















Energetic state of a bodyAny body the temperature of which is above 0 K radiates energy.				Equilibrium state				Non-equilibrium

Слайд 4Units and notions
The unit of radiant energy is Joule (J)

or kJ, mJ, hJ.
The basic characteristics of radiation is FLUX

of RADIANT ENERGY.
Amount of energy emitted (or passing) through the unit of area in a unit of time is termed SURFACE DENSITY of RADIATION FLUX or RADIOSITY.
It is also called simply Radiant flux or Flux of radiation.

Units:








Units and notionsThe unit of radiant energy is Joule (J) or kJ, mJ, hJ.The basic characteristics of

Слайд 5Wave nature of the radiant flux
Radiant energy spreads in form

of waves of different length. Distribution of energy in wavelength

is very important characteristics.
Let’s take wavelength interval from λ to dλ i.e. dλ.
Amount of energy emitted trough the body surface ds is proportional to ds and dλ


denotes monochromatic (homogeneous) flux of radiation. It represents the quantity to characterize the wavelength around λ. It is also called spectral density of radiation flux or emitting capability of the body or simply emittance.




Wave nature of the radiant fluxRadiant energy spreads in form of waves of different length. Distribution of

Слайд 7Absorption, reflection, transmission
As a monochromatic flux of radiation falls on

a body and passing through it, the flux is partly

absorbed, partly reflected, and the remaining part is allowed for transmission.




Absorption capability of the body (relative coefficient of absorption).
Reflection capability of the body (albedo).

Relative coefficient of transmission.
These coefficients depend on wavelength and properties of the body (Selectivity of the body)





















Absorption, reflection, transmissionAs a monochromatic flux of radiation falls on a body and passing through it, the

Слайд 8
Special properties of bodies

Absolutely Black body (Bb)

Absolutely White body (Wb)



(In

case of “geometric reflection” – specular body)
There are no

absolutely transparent bodies in the nature. Majority of solid bodies are not transparent.



If is large, is small (black soil). If is large, is small (Ice).
For a non-transparent body











Special properties of bodies			Absolutely Black body (Bb)Absolutely White body (Wb)(In case of “geometric reflection” – specular body)

Слайд 9
Transmission function for the atmosphere
The atmosphere is a transparent body.
Meteorologists

usually deal with some layers of it.

Monochromatic entering flux


Outgoing flux





Transmission

function


Transmission function for the atmosphereThe atmosphere is a transparent body.Meteorologists usually deal with some layers of it.								Monochromatic

Слайд 10Kirchhoff’s law
There is a good relation between absorption and emittance

of a body. The ratio Em/Ab does not depend on

the nature of the body. It is the same function B(λ,T) for every of bodies.
That’s Kirchhoff’s law.

For a Bb



In the nature there are no absolutely black bodies. Any real body emits and absorbs less energy of the same wavelength than Bb. However it emits and absorbs energy of the same wavelength.
M. Plank’s formula




Emittance of a BLACK BODY



Radiation constants

Kirchhoff’s lawThere is a good relation between absorption and emittance of a body. The ratio Em/Ab does

Слайд 11Gustav Robert Kirchhoff Wilhelm Wien
 1824 –1887
Born

Königsberg, Kingdom of Prussia
He coined the term "black body" radiation in 1862  


1864 –1928
born at Gaffken near Fischhausenborn at Gaffken near Fischhausen (Rybaki), Province of Prussia (now Primorsk, Russia)
In 1896 Wien empirically determined a distribution law of blackbody radiationIn 1896 Wien empirically determined a distribution law of blackbody radiation, later named after him: Wien's

Gustav Robert Kirchhoff      Wilhelm Wien  1824 –1887Born Königsberg, Kingdom of PrussiaHe coined the term 

Слайд 12Max Planck
1858 –1947
Planck was gifted when it came to musicPlanck was

gifted when it came to music. He took singing lessons and

played pianoPlanck was gifted when it came to music. He took singing lessons and played piano, organPlanck was gifted when it came to music. He took singing lessons and played piano, organ and celloPlanck was gifted when it came to music. He took singing lessons and played piano, organ and cello(Violoncello ), and composed songsPlanck was gifted when it came to music. He took singing lessons and played piano, organ and cello(Violoncello ), and composed songs and operasPlanck was gifted when it came to music. He took singing lessons and played piano, organ and cello(Violoncello ), and composed songs and operas. However, instead of music he chose to study physics.
Max Planck1858 –1947Planck was gifted when it came to musicPlanck was gifted when it came to music. He took

Слайд 131-st Wien’s law (Displacement law)
Distribution of energy in an absolute

Bb radiation spectrum is not homogeneous. It depends on the

body temperature. Suppose:






There is one wavelength (λm) where radiant energy is maximal.
The λm value depends on the body temperature. The lower the temperature, the larger the λm value.








1-st Wien’s law (Displacement law) Distribution of energy in an absolute Bb radiation spectrum is not homogeneous.

Слайд 14Practical application of the 1 Wien’s law?

Practical application of the  1 Wien’s law?

Слайд 15
Much of a person's energy is radiated away in the

form of infrared light. Some materials are transparent in the infrared,

while opaque to visible light, as is the plastic bag in this infrared image (bottom). Other materials are transparent to visible light, while opaque or reflective in the infrared, noticeable by darkness of the man's glasses.

http://en.wikipedia.org/wiki/Black_body

Much of a person's energy is radiated away in the form of infrared light. Some materials are transparent

Слайд 16Temperatures of flames by appearance
The temperature of flames with carbon

particles emitting light can be assessed by their color:

Red
Just visible: 525

°C (980 °F)
Dull: 700 °C (1,300 °F)
Cherry, dull: 800 °C (1,500 °F)
Cherry, full: 900 °C (1,700 °F)
Cherry, clear: 1,000 °C (1,800 °F)
Orange
Deep: 1,100 °C (2,000 °F)
Clear: 1,200 °C (2,200 °F)
White
Whitish: 1,300 °C (2,400 °F)
Bright: 1,400 °C (2,600 °F)
Dazzling: 1,500 °C (2,700 °F)


http://en.wikipedia.org/wiki/Fire#Typical_temperatures_of_fires_and_flames
Temperatures of flames by appearanceThe temperature of flames with carbon particles emitting light can be assessed by

Слайд 17Some interesting results gained from the 1-st Wien’s law

Some interesting results gained from the 1-st Wien’s law

Слайд 18The total flux and 2-nd Wien’s law
The total flux of

Bb radiation includes energy of all wavelengths emitted by the

body.



After integration

2-nd Wien’s law





Stephan-Boltzman constant



The total flux and 2-nd Wien’s lawThe total flux of Bb radiation includes energy of all wavelengths

Слайд 19Grey body
Since in the nature there are no absolutely black

bodies, we may call all of them grey bodies.
The grey

body is a body the absorption capability of which is the same for every wavelength.


Radiation flux of any grey body can be presented as;




Grey bodySince in the nature there are no absolutely black bodies, we may call all of them

Слайд 20Extinction and Bouguer’s law
Notion of extinction
The term extinction means weakening

of the radiation energy as its flux passing through a

body (or atmospheric layer).
Extinction=absorption + diffusion
Bouguer’s law holds: the flux of radiation is extinguished proportionally to its intensity (Fλ), density of the medium it passes through (ρ), and the passing distance (dl).
is mass extinction index, its dimension is









Dimensionless


m


To make right hand part dimensionless
must be



Extinction and Bouguer’s lawNotion of extinctionThe term extinction means weakening of the radiation energy as its flux

Слайд 21Extinction (Ex) is function of absorption (Ab) and diffusion (Df).

However, Ab = Ab(λ), and Df = Df(λ). Hence, the

value of extinction index depends on λ too.
Volume extinction index (*)

Adopting
The volume extinction index is numerically equal to the relative value of the radiation flux extinction as the beam of rays passes through a unit distance.
As it follows from the formula (*), the value of the volume extinction index depends not only on the medium composition but also upon its density. Therefore, it can be applied in case of non-variable density.






Extinction (Ex) is function of absorption (Ab) and diffusion (Df). However, Ab = Ab(λ), and Df =

Слайд 22Sum up of the radiation laws
Bouguer’s law
2 Wien’s laws
Kirchhoff’s law
Radiant

energy brightness
Brightness - emittance relation in isotropic field of radiation
M.

Plank’s formula
Sum up of the radiation lawsBouguer’s law2 Wien’s lawsKirchhoff’s lawRadiant energy brightnessBrightness - emittance relation  in

Слайд 23Radiant energy brightness
Spectral interval





Radiant energy brightness is the amount of

radiant energy passing in a unit of time through a

unit of area perpendicular to the rays, as the energy is placed in wavelength interval dλ (μ) and the solid angle ω (sr. or Steradian )
Radiant energy brightnessSpectral intervalRadiant energy brightness is the amount of radiant energy passing in a unit of

Слайд 24







This formula shows the relation between EMITTANCE (Fλ) and radiant

energy BRIGHTNESS (Gλ)


This formula shows the relation between EMITTANCE (Fλ) and radiant energy BRIGHTNESS (Gλ)

Слайд 25Brightness - emittance relation in isotropic field of radiation

In case

the beam of rays spreading does not depend on the

direction, the field of radiation is considered to be isotropic, i. e.









Brightness - emittance relation in isotropic field of radiationIn case the beam of rays spreading does not

Слайд 26Definitions
Hour Angle of the Sun
The Solar Hour Angle of

the Sun for any local location on the Earth is

zero° when the sun is straight overhead, at the zenith, and negative before local solar noon and positive after solar noon. In one 24-hour period, the Solar Hour Angle changes by 360 degrees (i.e. one revolution).

Solar Noon (and Solar Time)
Solar Time is based on the motion of the sun around the Earth. The apparent sun's motion, and position in the sky, can vary due to a few things such as: the elliptical orbits of the Earth and Sun, the inclination of the axis of the Earth's rotation, the perturbations of the moon and other planets, and of course, your latitude and longitude of observation. Solar Noon is when the sun is at the highest in the sky, and is defined when the Hour Angle is 0°. Solar Noon is also the midpoint between Sunrise and Sunset.

Sun Declination
The Declination of the sun is how many degrees North (positive) or South (negative) of the equator that the sun is when viewed from the center of the earth. The range of the declination of the sun ranges from approximately +23.5° (North) in June to -23.5° (South) in December.

DefinitionsHour Angle of the Sun The Solar Hour Angle of the Sun for any local location on

Слайд 28
Altitude (or Elevation)

First, find your azimuth. Next, the Altitude

(or elevation) is the angle between the Earth's surface (horizon)

and the sun, or object in the sky. Altitudes range from -90° (straight down below the horizon, or the nadir) to +90° (straight up above the horizon or the Zenith) and 0° straight at the horizon.

Azimuth

The azimuth (az) angle is the compass bearing, relative to true (geographic) north, of a point on the horizon directly beneath the sun. The horizon is defined as an imaginary circle centered on the observer. This is the 2-D, or Earth's surface, part of calculating the sun's position. As seen from above the observer, these compass bearings are measured clockwise in degrees from north. Azimuth angles can range from 0 - 359°. 0° is due geographic north, 90° due east, 180° due south, and 360 due north again.

http://www.esrl.noaa.gov/gmd/grad/solcalc/glossary.html

Altitude (or Elevation) First, find your azimuth. Next, the Altitude (or elevation) is the angle between the

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