Temperature of the Sun emitting surface

Average distance between the Sun and the Earth

r 149,5 106 km

0

a 696,6 103 km

And the radius of the sun is

r

r0

Every m2of the sphere of the radius

0

in one second receives the energy

I0* 1,37 kW m2 . The Whole sphere receives

all the energy emitted by the Sun

4 a2 B 4 r2 I*

r

2

*

B

T

4

s

0 0

B

0

I

s

a

0

s

s

T 4

B

5805k

s

s

This temperature is also called effective (radiation) temperature of the Sun.

For practical purposes it adopted to be 6000 K

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Difference between the insolation in Northern and southern hemispheres is explained by the eccentricity of the EARTH ORBIT

22 June (Aphelion) r 1,52 108 km

22 December (Perihelion) r 1,47 108 km

r 5000 000km

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Distribution of the Sun energy in various areas of the spectrum

UV (	0,39	) – 9%
Visible Light ( 0,39 0,75 ) – 47%
IR (	0,76	) – 44%

99% of the energy falls to the area 0,1 – 4,0 μ.

Conclusion: The Sun emits Short wave radiation.

100% of the terrestrial radiation (Earth’s radiation) falls to the area 3 – 120 μ (maximal 10μ).

Conclusion: The Earth emits Long wave radiation.

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Solar radiation distribution over the globe

We’ll consider the distribution over the upper “boundary of the atmosphere”, where the astronomical factors only may be accounted for

•Rotation of the Earth about the Sun.

•The tilt to ecliptic of the earth spinning axis.

•The Earth spinning.

At an arbitrary chosen moment of time the distance between the Sun and the Earth is not necessarily equal to the average one, i. e.

r r	4 r	2	I		4 r	2	I	*					I0*
0
				0	0			0		I0
													r	r	2
														0

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Insolation

The flux of solar radiation falling on a horizontal surface is called

INSOLATION

	B		I0 AB I0' AC
	ξ						'
		C	AB AC sin				I0 I0 sin
	A
	denotes altitude of the Sun above horizon (or just SUN ALTITUDE)
sin sin sin cos cos cos				2	t	Here, φ is latitude, δ is declination
						of the Sun, П=86400 s is duration
	of the one spin of the earth, 2 t is hour angle, and t is time being counted
	from the noon.
Let us determine amount of SR Q arriving to one m2of a horizontal surface
	during a day time at the top of the atmosphere, i. e. diurnal insolation.

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t0 Denotes time of sunrise

t0

Q I0' dt

t

0

Denotes time of sunset

At

t0 sin 0

t0

sin sin sin cos cos cos

2

t0 0

2

cos

2

t0 tg tg

sin sin cos cos cos

t0

t0 t0 ,

I0*

'

I0 sin

I0

I0

I0*

2

2

'

r

I0

sin sin cos cos cos

t

r

r

2

r

0

0

			*				t0	t0	2
		I0
Q						sin sin	dt cos cos cos			tdt
		r			2
			r				t0	t0
			0

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			*					t0	t0	2
		I0
Q						sin sin		dt cos cos cos			tdt
		r			2
								t0	t0
			r
			0

sin sin

t0dt

2t

0

sin sin

cos axdx 1 sin ax

a

t0

t0

2

2

2

2

cos

dt

sin

t0

sin

t0

2

sin

t0

2

t0

2

Q

2I0*

t

sin sin

cos cos sin

2

t

r

2

0

2

0

r

0

Calculation made from this formula allowed obtaining following distribution of the insolation over the globe.

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The Q values in summer of the Southern hemisphere are bigger than corresponding values for the Northern hemisphere. This is due to the Earth is close to its orbit aphelion during the Northern hemisphere mid-summer (the distance from the Sun is about 1.52*10 8 km), while at the midsummer

of the Southern hemisphere the Earth is close to its orbit perihelion (the distance from the Sun is about 1.47 * 10 8 km).

Because of the eccentricity e the seasons duration at Southern hemisphere is different from that of Northern hemisphere. Therefore, mean diurnal insolation values at Northern hemisphere differ from those of Southern hemisphere.

In summer, the Southern hemisphere atmosphere top receives a bit more radiation than that in Northern hemisphere. In winter, one can observe the vice versa.

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