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BECHER
creating a net loss of radiation. This phenomena is of sufficient
importance to warrant a closer study. Three quarters of solar radiation
has wave lengths less than 1 micron, and at point of maximum intensity
the wave length is less ian 0.5 micron. Terrestrial radiation has a
wave length of approxin. aly 12 -..crons at its point of maximum intensity.
. The cube of solar wave .sngth 1s mmall compared to the volume occupied
by a volcanic dust particle which has a diameter of 1.85 micron, but the
cube of terrestrial wave length is large compared io the same dust particle,
Then, as Lord Rayleigi has shown, solar radiation will be diffusely
reflected by the volcunis dust, but terrestrial radiation will be randomly
scattered,
I, ale
Ey -Ee
The following relations apply:
-2np r* x
3
(for reflection)..........iqn 1
4
~-lpnyV/a
(for
scatter). ..csccccesselGn
2.
Where x and y are distances of uniformly dusty regions. I and E are initial
intensities of solar and terrestrial radiation respectively.
I, and
are intensities after radiation has passed through a uniformly
dusty region.
n = number of particles in the dusty layer
radius of particles
r
V = volume of a single particle
at
~
& = wave length
3.1416
From Equations one and two we get
y/x=2 a4 r*/ll p* Vv" = 30
approximately
This means that a layer of volcanic dust of 1.85 micron diameter in the
atmosphere is thirty fold more effective in shutting solar radiation out
than it is in keeping terrestrial radiation in. This is in reality an
inverse Greenhouse effect which would ultimately lower the equilibrium
temperature of the surface of the earth if the dusty layer is maintained
aloft indefinitely.
Particles with diameters in the order of one half of
sun's wave length or less shut out the solar radiation very much more
effectively. This is because in the case of particles with such small
diameters (0.2 micron or less) both solar and terrestrial radiation is
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