Physical Oceanography, Vol. 16, No. 1, 2006
MESOSCALE STRUCTURE OF THE FIELDS OF VERTICAL VELOCITY AND
VORTICITY OF WINDS OVER THE BLACK SEA
V. S. Barabanov, V. V. Efimov, and M. V. Shokurov
On the basis of a simple stationary linear model and a contemporary nonlinear model, we study
the mesoscale characteristics of the fields of vertical velocity and vorticity of winds over the
Black Sea. It is shown that, in the idealized case (without taking into account the coastal fea-
tures), the temperature contrast between the land and the sea in both models leads to the forma-
tion of circulation cells in the coastal zone. However, the mountainous features prove to be the
main factor affecting the process of circulation for the actual synoptic situations. We present the
map of monthly average vorticity of the surface winds constructed according to the nonlinear
mesoscale model with a resolution of
for January 1996–2001.
The mesoscale characteristics of the surface winds over the Black Sea are formed under the action of num-
erous factors, among which the most important role is played by the coastal features and the temperature contrast
between the land and the sea. The investigation of these factors seems to be quite actual for the simulation of the
wind circulation of sea waters. The estimates presented in  demonstrate that the annual course of vorticity of
the surface wind can be regarded as a determining factor in the investigation of the seasonal cycle of currents in
the Black Sea and, in particular, of the Rim Current. However, the fields of surface winds of the NCEP/NCAR
reanalysis  used in  have a quite poor spatial resolution
and, hence, can be used for making only the
most general conclusions concerning the properties of wind circulation of the sea. In the last decade, the prob-
lem of detailed simulation of the circulation of Black-Sea waters becomes quite urgent . For the solution of
this problem, it is necessary to have the fields of surface winds with spatial resolutions not worse than several
tens of kilometers. In the present work, we discuss the possibility of construction of the required fields on the
basis of a mesoscale model of the atmosphere and consider (in detail) the physical mechanisms of formation of
the regional characteristics of the fields of vertical velocity and vorticity of the winds.
Influence of Temperature Contrast in the Linear Model
Following the method proposed in , we, first, consider the influence of the horizontal inhomogeneity of
the properties of the underlying surface on the formation of the wind field. The indicated inhomogeneity con-
nected with the difference of heat flows over the sea and surrounding land is taken into account under the as-
sumption that the orographic factor is absent (the model is based on the use of the flat coastal topography). In
the winter season, the difference between the heat flows from the sea and surrounding land into the atmosphere
is positive. This leads to the formation of cyclonic vorticity of the winds on the sea surface due to the presence
of the upward vertical velocity and the corresponding convergence in the atmospheric boundary layer. In sum-
mer, the negative difference of the heat flows leads to the formation of the downward vertical velocity over the
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol.
Translated from Morskoi Gidrofizicheskii Zhurnal, No.
52–61, January–February, 2005. Original article submitted December
42 0928-5105/06/1601–0042 © 2006 Springer Science+Business Media, Inc.