Physical Oceanography, Vol.
ANALYSIS OF THE VARIABILITY OF THE OPTICAL PROPERTIES OF
WATER IN THE BLACK SEA IN SUMMER 1998 ACCORDING TO
THE DATA OF A SeaWiFS SATELLITE INSTRUMENT
V. S. Suetin, V. V. Suslin, S. N. Korolev, and A. A. Kucheryavyi
We study examples of surveys of the Black Sea performed with the help of a SeaWiFS satellite
instrument. It is shown that the results of measurements carried out in spectral channels of
give information on the basic specific features of the space and time variability of
the characteristics of absorption and scattering of light in seawater. The use of a spectral channel
is inefficient due to the low reliability of the results of the procedure of atmospheric
correction performed according to standard algorithms. The results of model calculations de-
monstrate that the predominant contribution to the absorption of light in the Black Sea in summer
is made by the yellow substance.
A SeaWiFS optical scanner (USA) launched in the outer space in 1997 performs regular monitoring of
seas and oceans in several modes within a broad field of view . Radiation is recorded with high accuracy in
eight spectral intervals
in width located inside the wave band
nm. The accumulated data
can be useful for the solution of a broad class of scientific and practical problems—from global ecological
monitoring to the analysis of various local processes running in separate seas and coastal regions. In principle,
the results of simultaneous measurement of radiation in a collection of spectral intervals can be used to find the
concentration of chlorophyll and the values of other important parameters specifying the optical properties of
seawater [1–8]. To solve these problems in the most general statement, it is necessary to introduce the exact
atmospheric correction and determine the values of the normalized spectral brightness of water L
()λ for at
least the entire collection of wavelengths λ used for the SeaWiFS measurements.
At the same time, there are many indications that the reliability of the results of atmospheric correction for
the SeaWiFS spectral channels with
is doubtful [8, 9]. Thus, in many cases, the values of
()412 and L
()443 computed according to the standard algorithms are negative. Since similar explicit
signs of errors in the results of evaluation of L
()510 and L
()555 are absent, we focus our attention on
the analysis of the data for these two characteristics of seawater. We study examples of surveys of the west part
of the Black Sea in summer 1998. In summer, this region is characterized by insignificant cloudiness and, there-
fore, it is possible to perform almost regular monitoring of the Black Sea within the wavelength band of visible
light. The values of L
()λ used in the present work were obtained as a result of standard processing of the
SeaWiFS data performed by NASA according to the updated algorithms (version 2000) .
Typical examples of the space distributions of L
()555 for various days in June, July, and August 1998
are presented in Fig.
1. The maps shown in Fig.
1a, b, d are plotted according to the data of surveys made during
a single flight of the satellite over the Black Sea. Due to the noises caused by cloudiness, the map in Fig.
plotted according to the data of surveys made for two flights of the satellite over the sea (on July 19 and 20).
The time dependences of
and other parameters for a period from May till August 1998 are shown in
2. The values used to plot these curves were obtained as a result of averaging over the area of the analyzed
region chosen in the deep-water part of the sea and bounded between
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol. Translated from Morskoi Gidrofizicheskii Zhurnal,
35–45, November–December, 2002. Original article submitted May 7, 2001.
0928-5105/02/1206–0331 $27.00 © 2002 Plenum Publishing Corporation 331