Physical Oceanography, Vol. 19, No. 5, 2009
ANALYSIS OF OBSERVATIONS AND METHODS FOR CALCULATING
HYDROPHYSICAL FIELDS IN THE OCEAN
BREEZE CIRCULATION IN THE BLACK-SEA REGION
V. V. Efimov and V. S. Barabanov
We study the characteristic features of the breeze circulation in the Black-Sea region according
to the data of the regional reanalysis of atmospheric circulation carried out on the basis of the
MM5 mesoscale model for August 2007 by the method of difference composites. The applica-
tion of high space resolution of the model (the step of the grid is equal to
km) allows us to re-
produce the principal features of the sea and land breezes on c the composite maps. It is shown
that the space structure of breeze circulation is determined by the configuration of the coastline
and coastal orography.
Breeze circulation is formed as a result of the existence of temperature contrast between the sea and dry
land whose value and sign undergo daily variations. The day breeze (also called sea breeze) is caused a more in-
tense heating of the dry land as compared with the sea and, hence, by the process of elevation of heated air over
the coastal regions of dry land, the inflow of colder humid air from the sea to dry land in the lower layer of the
atmosphere, the corresponding reverse flow of air in the upper layers of the boundary layer of the atmosphere,
and its subsequent lowering over the sea. In the course of day-time heating, the development of sea breeze over
the land is accompanied by the formation of a front propagating for large distances from the coast (up to 100–
and the formation (as a result of baroclinic instability) of waves in the region of high vertical gradients
of the velocity (in the transient zone between the direct and reverse currents).
The night breeze (usually called land breeze) has the opposite direction as compared with the day breeze.
The temperature drop is formed as a result of the more pronounced thermal inertia of the upper layer of the sea.
Indeed, at night, the temperature of the dry land becomes lower than the temperature of the sea surface due to the
radiation cooling. This leads to the formation of a circulation cell opposite to the daytime cell. The intensities of
the sea and land breezes depend, first of all, on the difference between the day and night temperatures of the sur-
face air over the dry land and the sea depending, in turn, on the season of the year and the regional specific fea-
tures of the sea–land zone. However, as a rule, these two phases of daily variations of the breeze are asymmetric
and the development of the night breeze is weaker than the development of the day breeze. As the main cause of
this asymmetry, we can mention the difference between the stratifications of the boundary layer: The presence of
stable stratification of the boundary layer at night suppresses the development of the breeze, whereas the unsta-
ble stratification observed during the daytime promotes the intensification of the sea breeze .
The presented simple scheme of the development of breeze circulation is significantly complicated by the
action of several factors: First, the action of the Coriolis force leads to the rotation of the vector of the field of
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol, Ukraine.
Translated from Morskoi Gidrofizicheskii Zhurnal, No.
23–36, September–October, 2009. Original article submitted July 3,
2008; revision submitted August 28, 2008.
0928-5105/09/1905–0289 © 2009 Springer Science+Business Media, Inc. 289