Physical Oceanography, Vol. 19, No. 6, 2009
A SPECTRAL MODEL OF UNDERWATER IRRADIANCE IN THE BLACK SEA
T. Ya. Churilova,
V. V. Suslin,
and H. M. Sosik
We develop a semiempirical spectral model of penetrating irradiance taking into account the bio-
optical characteristics of the Black Sea. The evaluation of the contributions of the principal opti-
cally active components to the total absorption of light in the sea shows that, in the short-wave
light is mainly absorbed by the dissolved organic matter
contribution of phytoplankton to the total absorption attains its maximum values
(26–37%) in the
abyssal part of the sea in the period of spring blooming of diatoms. In the coastal waters, the ab-
sorption of light by suspended nonalgae particles in summer is almost twice as intense
as in the open sea
(8–13%). The analysis of the sensitivity of our model shows that the
absorption of light by dissolved organic matter is more significant for the estimation of the pho-
tosynthetically active radiation in the Black Sea than the concentration of pigments and back-
scattering of light by suspended particles. The comparison of the results of model computations
with the data of measurements of the underwater irradiance reveals high accuracy of the pro-
The light field in the sea is determined by the flux of solar energy incident on the sea surface and the optical
properties of marine media, i.e., by the absorption and scattering of light . About a half of the total amount of
solar energy corresponds to the photosynthetically active radiation (PAR) in the wavelength range
The solar energy penetrating into the water masses is absorbed and scattered by water and various substances
suspended and dissolved in water. The coefficients of absorption and scattering of light depend on the concen-
tration of phytoplankton and its pigment composition, and the contents of dissolved organic matter, organic det-
ritus, and inorganic suspended substances. Until recently, only a few measurements of the spectral coefficients
of absorption of light by suspended matter were available for the Black Sea . The procedure of determination
of the Secchi-disk depth was used for the evaluation of the transparency of water especially extensively . In
the last decade, numerous measurements of the absorption of light by phytoplankton and suspended and dis-
solved substances were performed in the Black Sea [4–7]. On the basis on the accumulated results, the absorp-
tion of light was parametrized by the principal optically active components with high spectral resolution, and the
seasonal and regional specific features of the biooptical characteristics in the Black Sea were established .
Even earlier, a possibility of correct estimation of the scattering of light based on the satellite data was demon-
The aim of the present work is to develop a regional semiempirical spectral model of PAR taking into the
account the biooptical characteristics of the Black Sea.
Kovalevskii Institute of the Biology of Southern Seas, Ukrainian Academy of Sciences, Sevastopol, Ukraine.
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol, Ukraine.
Woods Hole Oceanographic Institution, Woods Hole, USA.
Translated from Morskoi Gidrofizicheskii Zhurnal, No.
33–46, November–December, 2009. Original article submitted August
14, 2008; revision submitted September 24, 2008.
366 0928-5105/09/1906–0366 © 2009 Springer Science+Business Media, Inc.