Analysis of Radiative Observations in Cloudy Atmosphere - Short-Wave Solar Radiation in the Earth's Atmosphere - page 248

to sea salt (namely to NaCl) content in the atmospheric aerosols according to
the study by Ivlev and Andreev (1986).
The atmosphere in the Arctic regions is purer - the conservative scatter-
ing becomes apparent within a large range of wavelength (Fig. 7.2d, experi-
ment 11). Spectral values (1-

ω 0 ) retrieved from airborne experiments 3 and
7 (Fig. 7.2b,c) and from the satellite experiments (certain parts of the curves
in Fig. 7.11, 3) demonstrate a monotonic increase with wavelength that can
be attributed to organic fuel combustion (Sokolic 1988). The values of single
scattering co-albedo (1- ω 0 )obtainedfromairborneexperiments1,2and5

and most pixels of the satellite images show no spectral dependence, which is
typical for the black carbon and dust aerosols.
Consideration of volume absorption coefficient

κ of the separate cloud sub-

layers (Fig. 7.4) indicates strong vertical inhomogeneity. The upper curves in
Fig. 7.4b demonstrate significant absorption by two upper cloud sublayers cor-
responding either to the oxygen and water vapor absorption bands (0.68, 0.72,
0.76

µ µ

m). Two
lower sublayers show the opposite spectral dependence. It could be explained
with the higher content of ozone in the upper tropospheric layers compared
with the lower ones. The results of experiment 7 show the monotonic increase
of the absorption coefficient with wavelength in the bottom layer (1.0-1.1 km).
A similar result has beenmentioned above for the cloud, considered as a whole
layer.
Inspiteofsignificantuncertaintiesoftheretrievalofvalues(1−

m) or to the ozone Chappuis molecular absorption band (0.65

ω 0, i )and

τ i the obtained result demonstrates the rather real magnitudes and
spectral dependence coinciding with the results of considering the cloud layer
as a whole. Using the spectral dependence of the irradiances promotes dimin-
ishing the uncertainties of the retrieval because the results obtained for the
neighbor wavelengths do not distinguish strongly from each other. Smoothing
over spectral values out of the absorption bands could be rather effective for
obtaining the real values of the optical parameters.
Several pixels of the satellite images (in Fig. 7.11, 1) are characterized with
magnitude 0.05 for value (1−

especially

ω 0 ). It could be concluded that the observational
errors increases at the edges of the image, especially for the single pixels with
the strong absorption. However, the other parts consist of several pixels with
the higher absorption and could correspond to the industrial regions with the
increasing content of the soot aerosols. Only some rare pixels above the ocean
are characterized with the conservative scattering of radiation.

7.4.2
Optical Thickness τ 0 and Volume Scattering Coefficient α

The values of volume scattering coefficient

α

vary strongly in different exper-

α λ iments. Spectral dependence ) demonstrates the strong vertical inhomo-

geneity of the cloud, and both the magnitudes and the spectral dependence are
different in different cloud sublayers. It reflects the inhomogeneity of the mi-
crophysical cloud structure. The volume scattering coefficient obtained for the
cloud as a whole coincides with the averaged values obtained for the separate

(