Physical Oceanography, Vol. 14, No. 1, 2004
MANIFESTATION OF SPECIFIC FEATURES OF THE OPTICAL PROPERTIES OF
ATMOSPHERIC AEROSOL OVER THE BLACK SEA IN THE INTERPRETATION
OF SEAWIFS DATA
V. S. Suetin, S. N. Korolev, V. V. Suslin, and A. A. Kucheryavyi
We consider the problem of quantitative evaluation of the optical characteristics of seawater ac-
cording to the data of satellite measurements. The principal physical mechanisms responsible for
the errors in the atmospheric correction made with the help of the standard NASA algorithm are
established. It is shown that the models of atmospheric aerosol realized with the help of this al-
gorithm are inconsistent with its actual properties over the Black Sea.
The Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) satellite instrument operating in the visible region
of the electromagnetic spectrum can be useful for a broad class of investigations . Some results of observa-
tion of the Black Sea can be found in [2–4].
The values of radiance of the sea measured from the space are strongly corrupted by the atmosphere. The-
refore, the procedure of quantitative evaluation of the optical and biological parameters of seawater based on the
simultaneous measurements of radiance in several narrow spectral bands requires the application of a special
atmospheric correction. In the general case, the problem of atmospheric correction is quite complicated [5, 6].
For this reason, in practice, it is solved by using more or less simplified methods and algorithms. Thus, the stan-
dard procedure of processing the SeaWiFS data [7, 8] is based on the parametrizations of a limited number of
models of the optical properties of aerosols. Actually, this procedure was created for processing the data of mea-
surements over the ocean and, in view a great variety of the optical properties of aerosols described in , it
could be expected that, in the general case, the results of its application to water areas similar to the Black Sea
would be unreliable. The analysis of practical results shows that, in many cases, this is true [3, 4].
The aim of the present work is to study the causes and physical mechanisms of the appearance of several
noticeable errors in processing the SeaWiFS data according to the standard algorithm proposed by the National
Aeronautics and Space Administration (NASA). In the present work, we restrict ourselves to the analysis which
can be performed (without using control subsatellite measurements) by comparing the sets of remote data ob-
tained in several spectral bands for different days within the limits of the same chosen test region of the sea with
presumably constant optical properties of water. We use the data of the SeaWiFS surveys carried out over the
Black Sea on August 1, 2, and 4, 1998 in the Global Area Coverage (GAC) mode. To process the source data
represented in the Level-1a format, we use the SeaWiFS Data Analysis System (SeaDAS) software package
developed by NASA specially for the realization of the standard procedure of processing the SeaWiFS data.
In the indicated days, the cloudiness over the Black Sea was quite low, but the density of aerosol was high.
This enabled us to use the results of satellite observations for testing the procedure of atmospheric correction.
An example of evident errors in performing atmospheric correction according to the standard NASA algorithm
for the surveys of the Black Sea carried out on 08.02.98 in a channel of
is presented in . As a result
of the atmospheric correction, we get the so-called normalized spectral radiance of the sea
is a wavelength of optical radiation. The schematic maps of the quantities
) for the western part of the Black Sea on 08.02.98 are presented in Fig.
1. This figure
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol. Translated from Morskoi Gidrofizicheskii Zhurnal,
69–79, January–February, 2003. Original article submitted July 4, 2002.
0928-5105/04/1401–0057 © 2004 Plenum Publishing Corporation 57