Analysis of Radiative Observations in Cloudy Atmosphere - Short-Wave Solar Radiation in the Earth's Atmosphere - page 251

its components. However, we don't aim here to consider the mathematical
aspectoftheproblem,thusweproposetheempiricalapproach,presentedin
several studies (Melnikova 1989, 1997; Kondratyev et al. 1997; Melnikova and
Mikhailov 2000).
Usually the scattering or absorption coefficients of the whole medium are
presented as a sum of the corresponding coefficients of separate components.
Specify the optical parameters relating to the molecular component with M ,
relating to the aerosol component with A , and relating to the droplets with D .
Then the usual notation looks like:
α = α M + α A + α D ,

(7.1)

κ = κ M + κ A .

Accounting for the mutual influence of the scattering and absorption by dif-
ferent components, we propose the empirical relations:

p
D

q
0 +

α = α M + α A ) C τ ω α D , (

(7.2)

p
D

q
0 ,

κ = κ M + κ A ) C τ ω (

ω 0 isthesinglescatteringalbedo, C isthefactorofproportionality,
τ D and

where

α D are the optical thickness and the volume scattering coefficient
caused only by scattering by droplets (value of

τ 0 in Fig. 7.1 and value of α

κ A are the values of scattering and
absorption coefficients ofmolecules and aerosol particles in the clear sky (

λ µ α M , α A , κ M , in Fig. 7.12a for > 0.8 m),

α M is
a coefficient of Raleigh scattering) at corresponding wavelength and altitude of
the atmosphere; p and q are the empiric coefficients, estimated in several studies
(Melnikova 1989, 1992, 1997; Kondratyev et al. 1997; Melnikova and Mikhailov
2000). The coefficient of scattering by droplets α D has no factor because the

Fig. 7.12a,b. Spectral dependence of the volume coefficients ( a -scatteringand b -absorp-
tion) of the stratus cloud, retrieved from the data of the experiments, numbered as per
Tab l e 3 . 2