Analysis of Radiative Observations in Cloudy Atmosphere - Short-Wave Solar Radiation in the Earth's Atmosphere - page 235

Analysis of Radiative Observations
in Cloudy Atmosphere

7.1
Optical Parameters of Stratus Cloudiness Retrieved
from Airborne Radiative Experiments

The data of airborne experiments accomplished in 1970-1980-th within the
range of research programs CAENEX, GATE, GARP have been presented in
Sect. 3.3 with the results of the experiments under the overcast conditions
being listed in Table 3.2. These results are used here for inferring spectral
dependence of the optical parameters of cloud layers (optical thickness τ 0

ω 0 ), applying the approach described in Chap. 6
(Melnikova 1989, 1992; Melnikova and Mikhailov 1993,1992). The spectral
values of phase function parameter g , needed for obtaining optical thickness

and single scattering albedo

τ 0 ,

ω 0 , and the volume scattering coefficient are taken
from the study by Stephens (1979). The procedure of retrieval is presented in
detail elsewhere (Melnikova 1992, 1997; Melnikova and Mikhailov 1994).

single scattering albedo

7.1.1
Analysis of the Results of Radiation Observations in the Tropics

The observations were carried out as a part of the GATE experiment above the
Atlantic Ocean close to the west coast of Africa (experiment No. 1: 12th July
1974, the latitude was 16 ◦ N, experiment No. 2: 4th August 1974, the latitude
was 17 ◦ N). The cloud bottom and top were at altitudes 0.3-3.3 and 0.5-5.0 km
for experiments 1 and 2 correspondingly. The uncertainties of the observations
were about 5-7%depending on wavelength. The retrieval of the optical param-
eters was implemented for every wavelength independently using (6.1). The
spectral values of optical thickness ω 0 )

are shown in Figs. 7.1a and 7.2a correspondingly and the volume absorption
and scattering coefficients are shown in Table A.12 of Appendix A. The oscil-
lations in the curves presenting the optical thickness in Fig. 7.1a are explained
with the high observational uncertainties; the smoothed curves are figured
there as well. It should be mentioned that the high values of single scattering
co-albedo (1 −

τ 0 and single scattering co-albedo (1 −

ω 0 ) are explained with the strong flue sand escaping from the
Sahara Desert to the observational site.