Physical Oceanography, Vol.
NUMERICAL SIMULATION OF THE SEASONAL VARIABILITY OF
HYDROPHYSICAL FIELDS IN THE BLACK SEA
S. G. Demyshev, V. V. Knysh, and G. K. Korotaev
We present a brief description of a nonlinear numerical model used to reproduce the variability
of large-scale circulation in the Black Sea under the action of seasonal boundary conditions. The
calculated circulation is of cyclonic nature. The Main Black Sea Rim Current is presented for
the whole year and flows along the continental slope. In the upper layers, seasonal variability
manifests itself in the intensification of the Rim Current in winter, especially in the eastern part
of the sea. In the annual average, we observe elevation in the central part of the sea and lowering
on its periphery. In winter, we see strong elevation in the eastern part of the sea and lowering in
its western part. In spring, we observe the opposite situation. In summer, the structure of verti-
cal motions changes again and corresponds to the winter type. In autumn, it again becomes sim-
ilar to that recorded in spring. The formation of a cold intermediate layer occurs as a result of
the action of two mechanisms. In the central part of the basin, it is caused by the winter convec-
tion and, on the periphery of the main cyclonic circulation, by the formation of cold waters in the
northwestern part of the sea, their subsequent lowering along the continental slope, and transpor-
tation by currents along the coast.
The Black Sea is an almost closed basin. For various reasons, the discharge of large European rivers into
the Black Sea is seriously polluted. Therefore, the analysis and prediction of the ecological situation in this re-
gion is an extremely urgent problem. For its solution, it is necessary to have a good-quality hydrodynamical
model capable of adequate reconstruction of the fields of temperature, salinity, and current velocity.
A discrete hydrodynamical model of a closed basin was proposed in . In , it was applied to the speci-
fic conditions of the Black Sea. The results obtained in  demonstrate that this model is quite promising and
requires subsequent development. In the present work, we propose a version of this model in which boundary
conditions are formulated more precisely and, in particular, the inflow of rivers and the effect of Bosporus are
taken into account.
One of the main problems encountered in the investigation of the dynamics of the Black Sea is connected
with the reproduction of the seasonal variability of hydrophysical fields. The first numerical calculations aimed
at the analysis of the seasonal variability of circulation in the Black Sea were performed in  and continued in
In the present work, we consider a prognostic problem of the formation of three-dimensional circulation
under the action of boundary conditions varying from season to season. A similar statement of the problem was
realized in the experiments carried out in  but with the Dirichlet boundary conditions for temperature and sali-
nity imposed on the sea surface. In the present work, unlike , where the inflow of rivers was taken into ac-
count only in the northwestern shelf zone, we use a more precise distribution of the inflow of rivers along the
periphery of the Black Sea (taking into account the rivers of the Caucasian Coast and Turkey).
The aim of the present work is to demonstrate the efficiency of the proposed numerical three-dimensional
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol. Translated from Morskoi Gidrofizicheskii Zhurnal,
12–27, May–June, 2002. Original article submitted September 21, 2000; revision submitted April 2, 2001.
126 0928-5105/02/1203–0126 $27.00 © 2002 Plenum Publishing Corporation