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Figure 2.2
Spectra of shortwave radiation and longwave radiation and its absorption
in the atmosphere. (
a
) Black-body radiation from objects with temperatures of 5800 K
(surface of the Sun) and 293 K (representative of Earth and atmosphere); the radiative
lux densities have been normalized by the peak values (which differ by more than 6
orders of magnitude). (
b
) Total absorptivity of the atmosphere (US standard atmo-
sphere) for the most important absorbing species. (
c
) Total absorptivity for all species
together. The vertical dashed line separates shortwave and longwave radiation. Spec-
tra determined with the Reference Forward Model (
http://www.atm.ox.ac.uk/RFM/
,
based on GENLN2) (Edwards,
1992
), using the HITRAN2008 absorption line data-
base (Rothman et al.,
2009
) and ozone UV absorption from Brion et al. (
1993
).
2
↓
=
d
d
Sun
KI
cos(
θ
(2.3)
0
0
z
Sun
where
I
0
is the
so
lar constant (lux density of solar radiation at the mean distance from
Sun to Earth),
d
Sun
is the
mean
(over a year) distance between Sun and Earth,
d
Sun
is
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