Physical Oceanography, Vol. 18, No. 1, 2008
RETRIEVING OF THE BIOOPTICAL CHARACTERISTICS OF BLACK-SEA
WATERS UNDER THE CONDITIONS OF CONSTANT REFLECTANCE AT
A WAVELENGTH OF
E. B. Shibanov and E. N. Korchemkina
We consider a method used for the solution of the inverse problem of biooptics of the sea ac-
cording to the spectrum of upwelling radiation and propose a procedure for the correction of the
data of measurement by fixing the value of reflectance at a wavelength of
nm. The influ-
ence of this assumption on the results of retrieving of the concentrations of admixtures in seawa-
ter is analyzed. The computed values of the concentration of chlorophyll correspond to the data
of direct biological measurements, and the reconstructed spectra of the absorption coefficient of
phytoplankton have local maxima typical of biological particles. The applied correction allows
us to decrease the influence of measurement errors on the results of retrieving and to increase the
stability of solution of the inverse problem.
The reflectance of the sea proves to be the most convenient hydrooptical characteristic used in the global
investigations of the biooptical properties of surface waters. The spectrum of upwelling radiation depends on the
organic substances suspended and dissolved in seawater. Moreover, the number of unknown characteristics of
the medium is much larger than the number of measured parameters. The problem of evaluation of the charac-
teristics of water masses according to the data on reflectance is, in fact, a classical inverse problem.
The analysis of the data of satellite sea-color scanners is connected with taking into account the state of the
atmosphere in one or two spectral channels lying in the infrared spectral region. In this case, the accuracy of at-
mospheric corrections depends on the accuracy of satellite or a priori data on the spectral and angular char-
acteristics of light scattered on aerosol particles required for the extrapolation of the effect of haze from the in-
frared spectral region into the visible region. The indicated extrapolation can be responsible for large errors in
estimating the effect of haze and, hence, for significant errors in the subsequent evaluation of reflectance in the
short-wave part of the visible region. The available data on the specific features of the reflection of light by the
sea in the blue region enable one to significantly increase the accuracy of atmospheric corrections, e.g., in the
same way as in .
In the present work, on the basis of the analysis of the spectra of diffuse reflectance, we propose to impose
certain restrictions on the value of reflectance in the blue spectral region. Our aim is to study the influence of
these restrictions on the results of solution of the inverse problem for the data obtained from the surface. The in-
verse problem of biooptics is solved analytically.
This approach is characterized by higher informativity.
it enables one not only to retrieve the concentrations of optically active admixtures in seawater but also to repro-
duce the specific features of their absorption spectra under natural conditions and determine the level of back-
scattering by the particulate matter in the green spectral region.
Marine Hydrophysical Institute, Ukrainian National Academy of Sciences, Sevastopol, Ukraine.
Translated from Morskoi Gidrofizicheskii Zhurnal, No.
38–50, January–February, 2008. Original article submitted June 2, 2006;
revision submitted July 24, 2006.
0928-5105/08/1801–0025 © 2008 Springer Science+Business Media, Inc. 25