Hydrometeorological Coastal Integrated Research in
the North-Eastern Part of the Black Sea
V.S. Arkhipkin, S.S. Mukhametov
M.V. Lomonosov Moscow State University, 119991 Moscow, Russian
Federation
Tel: +7 495 9392215 Fax: +7 495 9328836
E-mail: victor.arkhipkin@gmail.com, 11May1978@gmail.com
Abstract
Department of Oceanography, Faculty of Geography of M.V.Lomonosov
Moscow State University engage in field observations of hydrometeorological
characteristics in the base of South Branch of the Shirshov Institute of Oceanology
Russian Academy of Sciences more than 10 years. The study area is varied topography,
occupies a mountain-foreland of the Caucasian Black Sea coast between the territories
of the cities Novorossiysk and Tuapse, a length of about 90 km and a width of 8 to 30
km.
During this work gained wide array of oceanographic observations in the coastal
zone of the north-eastern Black Sea. Studies are in the same time (late May - mid-July
and late January - early February), during this period held steady continuous
observation with a step for 5 minutes for the main meteorological parameters and
hydrological-chemical parameters of sea water (temperature, salinity, pH , redox
potential, dissolved oxygen, etc.), to engage in a comprehensive oceanographic survey
of Gelendzhik Bay area (30 stations). Surface water samples took that to determine the
hydrochemical parameters (pH, alkalinity, oxygen content, concentrations of phosphate,
silicate and nitrate concentrations of some pollutants such as petroleum products) in
laboratory conditions, as well as sampling for phytoplankton. Using Doppler profiler
observations were carried out for currents and with the help of an acoustic wave
recorder – wave observations and sea level.
Fig. 1: Area studies
Introduction
One of the distinguishing features of meteorological study area is the interaction
of breeze and mountain-valley atmosphere circulation. Spectral analysis of
observational data shows that the most energy-for the main meteorological variables (air
temperature, atmospheric pressure, longshore and normal to the shore components of
wind velocity) are variations of the daily periodicity. Contribution to the overall
variability of wind speed normal to the shore was equal to two times more than the
contribution of longshore component. This confirms the important role of local
circulation, as not only a breeze, but the winds of mountain-valley circulation
perpendicular coastline. Processes of large-scale energy transfer in the oceanatmosphere system associated with the thermal contrast of air and water, and phase
differences between the annual cycle of the thermal characteristics of the ocean and
atmosphere [Lappo, 2004]. Mesoscale interaction between the ocean and the
atmosphere is characterized by an exchange of properties and energy in the processes of
daily variability. Diurnal changes, as well as seasonal, are quasi-cyclic processes. This
circumstance allowed to apply to daily fluctuations, similar to the seasonal approach,
based on the consideration of two-parameter phase diagram [Lappo, Gulev,
Rozhdestvensky, 1990]. The rate of change in water temperature and the air is largely
controlled by the regime breeze circulation in the atmosphere.
To analyze the processes in the coastal zone has been applied numerical ocean
models, University of Bergen (BOM), adapted to the conditions of the study area. Grid
spacing along x and y - 75 m Number of sigma levels - 24. Experiments were conducted
to identify the characteristics of the reaction zone in the coastal waters of various
synoptic situations typical for the area.
The observations were made using an automatic weather station, "Vantage Pro"
by "Davis Instruments", an automatic oceanographic probe YSI 6600, ultrasonic wave
recorder remote «LOG_a Level» by «General Acoustics Company», Acoustic Doppler
Current Profiler by «RD Instruments». Hydro-meteorological observations were
conducted during the summer months (June-July) and winter (January-February) for 12
years (since 1999). Especially noticeable influence of local circulation on the weather
appears while easing the pressure of wind and large-scale atmospheric flows, where
over time, exceeding the characteristic period of meteorological processes, there is no
change of air mass. In this case, the nature of weather and diurnal variation of
meteorological variables is determined by properties located in the area of air masses,
particularly its moisture content, which depends on the radiation and, consequently, the
temperature regime. From this perspective, the study of meteorological processes on the
northeastern coast of the Black Sea summer period is the most appropriate. At this time,
the number of passing cyclones and atmospheric fronts decreases and the frequency of
days with breeze circulation may be from 50 to 100% (Burman, 1969).
Sections of the main text
Spectral density of air temperature, sq.deg/min
40000
30000
20000
10000
0
10000
1000
100
Period, min
10
The spectral density of the normal to the shore component of wind velocity, sq.m/sq.sec*min
Spectral analysis of our observational data shows that the most energy-carrier
for the main meteorological variables (air temperature, atmospheric pressure,
alongshore and normal to the shore wind velocity component) are the fluctuations of the
daily periodicity (1440 min). After eliminating the diurnal revealed two peaks of the
spectral density (Fig. 2a-b).
a)
b)
20000
16000
12000
8000
4000
0
10000
1000
100
10
Period, min
Fig. 2: The graphs of the spectral density normal to the shore component of wind
velocity (a) and spectral density of air temperature in summer days with breeze
circulation 1999-2011
The first corresponds to the period close to the semi-diurnal (10-17 h). This is
explained by the fact that daytime and nocturnal manifestations of local circulation
regimes (breezes, mountain-valley wind and slope winds) are independent processes.
The second maximum falls on the oscillation period 30-60 h (1,5-3 day). Contribution
to the overall variability of the wind velocity component normal to the coast two times
greater than the contribution of alongshore component. This fact confirms the important
role of local circulation, as not only a breeze, but the winds of the mountain-valley
circulation are perpendicular to the coastline.
In the Gelendzhik Bay aquatory regularly conducted comprehensive
oceanographic surveys of a single polygon, which contains about 30 stations (Fig. 3)
Latitude
44.585
8
21
7
6
44.58
20
22
44.575
5
9
18
23
44.57
4
10
19
17
24
3
11
12
44.565
16
44.56
15
29
44.555
2
13
25
1
14
26
28
27
44.55
38.025 38.03 38.035 38.04 38.045 38.05 38.055 38.06 38.065 38.07 38.075
Longitude
Fig. 3: The scheme of the stations at the site of Gelendzhik Bay
These works are taking place not only in favorable weather in the summer but in
winter time. One of the most interesting processes taking place on the shelf of northeastern part of the Black Sea in the winter – the formation of cold intermediate water.
Formation of cold intermediate and deep waters occurs primarily when compacted
during winter cooling (due to the impact of heat in the atmosphere and sea due to
evaporation) and salinity (due to evaporation) of surface waters. These two processes
are actively contributing to cold and dry continental winds. Cold winds increase the
cooling, strong and dry – increased evaporation. Strong winds also increased wind
mixing, which contributes to the destruction of the seasonal thermocline.
Meteorological conditions of the Black Sea in winter are characterized by frequent
westerly winds, which at times can be very strong, and bring to the surface of the sea is
cold, dry air from the continent (continental polar air, or even continental arctic air).
Water temperature at the surface of 9-7 °C and below, on the northwest shelf - to 0 °C,
while in the northern part of it - to the freezing point. In the Black Sea, on the one hand,
represented a vast north-west shelf of limited depth, strongly freshwater river runoff and
a smaller area of the northeastern shelf, on the other – the two main cyclonic gyre in the
open part. The main foci formation of intermediate cold waters of open sea in winter are
associated with anomalously cold and salty spots in the centers of cyclonic gyres of the
Black Sea. Permanent pycnocline is raised to 30-40 m and sometimes up to 20 meters,
so it delays the exchange of properties vertically particularly strong, and increased
density in the centers of most cycles. Convective mixing here, regardless of «severity»
winter conditions, may develop much earlier and stronger than in other parts of the open
sea.
Engaging in cyclonic circulation, the density currents generated on «domes»
feed layer minimum temperature, which is gradually spreading throughout the deep part
of the Black Sea and deepened in the continental slope to 100 m or more.
The sequence of formation of cold shelf waters in shallow areas of the shelf and
in bays can be considered an example of Gelendzhik Bay. The increase in density is
greatest, because the heat is removed from a thin layer and cooling more rapidly than in
other, more distant from Markotkh Ridge through which the inflow cold dry air in the
bay area. As a result, formed abnormally cold water is not very high salinity but
significant density. Thus, under the force of gravity is generated by the density of the
flow with downward movement of the slope of the shelf.
As seen in these images (Fig. 4,5), the lowest recorded water temperature in a
period of intense cooling was 4.4 °C, maximum 8.8 °C, and the depth of minimum
temperature, except for coastal areas, corresponds to the depth of the bay itself. At this
depth is the core of the emerging here of cold intermediate water.
These countervailing trends clearly visualized on the temperature and density
profiles constructed from the data section, normal to the wellhead alignment bay. Cold
shelf waters, reaching its sliding back depth of 35 m, dropped on to the continental
slope, and may be subject to the open sea.
Latitude
Longitude
Fig. 4: The distribution of the lowest water temperatures in Gelendzhik
Bay waters – the core of cold intermediate water
Studies had shown, the combination of favorable oceanographic and
meteorological factors on the northeastern shelf of the Black Sea (kinematics, water
structure, dynamics and properties of air masses) in the winter cooling of surface waters
causes that are located close to the low spurs of the Caucasus, the waters may form cold
intermediate water.
Depth, m
5
10
15
20
25
30
35
8.5
8.4
8.3
8.2
8.1
8
7.9
7.8
7.7
7.6
7.5
7.4
7.3
7.2
7.1
7
6.9
6.8
6.7
6.6
Fig. 5: The temperature distribution on the longitudinal section of 04/02/2008
Leading factor in this case supports a small depth. As a result of the restructuring
of the density field of winter there is the density currents, which are on the bottom of
the shallow depths to greater. However, we must take into account that the parameters
of the cold intermediate water reveal a strong dependence on the synoptic factors
(direction, duration and wind speed and air temperature), so the process of their
formation may be discrete in time and space in nature, slowing down and stopping, but
reopening new force, under favorable conditions.
Synoptic variability with time scales of the inertial period to the season - one of
the 5 major time-range variations in the state of the oceans and seas, along with interannually (many years), seasonal, diurnal and short-period range. However, it has
become apparent only in 1970-1980's. That can be considered the "golden age" in the
history of the problem. A comprehensive compilation of very numerous and important
results of oceanographic research done in this period (Blatov, Tuzhilkin, 1990). In
particular, it implies that the main carriers of synoptic variability in the oceans are:
1) forced to be immediately excited and supported by synoptic atmospheric
processes (drift currents away from the coast, coastal upwelling / downvelling,
deepening / shallowing bottom border of the upper mixed layer, etc.);
2) proper motion - subinertion gradient-vortex waves, Rossby, topographic,
coastal trapped, frontal;
3) mesoscale eddies of various kinds, as a result of hydrodynamic instability of
wave motions of the previous group. Among them, the whole of the oceans most
energetic eddies (Blatov, Tuzhilkin, 1990).
The exception in this sense is a coastal zone of the oceans and seas, including the
continental shelf and slope. Here most of the vortex collapses, forming a small shortlived vortices as a result of shear (horizontal gradient) between the rate of longshore
currents rod and the shore, creating a regime of chaotic variability is close to fully
developed turbulence in pipes and channels. The main carriers of the same distinct
synoptic signal in the shelf-slope area, along with upwelling / downvelling serve as
coastal trapped waves (CTW). Targeted and highly productive full-scale and theoretical
studies of these processes are performed in the same 1970-1980-ies. off the coast of
North and South America, Africa, Australia, Western Europe (see, eg, reviews Allen,
1980, Brink, 1982, 1983, 1991, Clarke, Thompson, 1984, Arkhipkin et al, 1987, Blatov,
Tuzhilkin, 1990 Ivanov, Jankowski, 1992), clearly showed a close genetic relationship
between them. Thus, coastal upwelling / downvelling almost always gives a good start
("triggers") CTW, which are distributed along the coast (leaving it in the northern
hemisphere on the right) as alternating regions of divergence / convergence of longshore
currents synoptic. Accordingly, these regions are associated with traveling in the same
direction of a "wave" upwelling / downvelling that the process of moving can "pump
up" the resonant wind effects (Clarke, Thompson, 1984, Brink, 1991). Depending on the
geometric parameters of the shelf and slope, and water density stratification periods
CTW ranged from 1 day to 2 weeks, the wavelengths - from tens to hundreds of
kilometers, the phase velocity of 3-4 m / sec. Extremely large and diverse application of
knowledge and scientific importance of these processes encourage them to intensive
research in most of the coastal ocean regions with active business operations.
In the Black Sea the first studies of synoptic variability in the coastal zone - the
wind-tide phenomena - were made long ago - a half century ago (Bogdanova, 1959,
Bogdanov, Kropachev, 1959, Tolmazin, 1963). Over the next 30 years, despite clear
evidence of high intensity of coastal upwelling, even he was given undeservedly little
attention. In particular, in the most popular books on hydrology and water dynamics of
the Black Sea (Filippov, 1968, Blatov et al, 1984, Hydrometeorology ..., 1991), this
question has not been considered at all. The results of the first modern systematic study
of coastal upwelling and CTW off the south coast of Crimea were set out in (Blatov,
Ivanov 1992, Ivanov, Jankowski, 1992, 1993). They showed a close similarity of the
properties of these processes in the Black Sea and in the above regions of the oceans.
However, even after they sufficient activity in these areas of research of the Black Sea
was not observed. It may be noted only a few full-scale and model studies of upwelling
in the same southern coast of Crimea (Gawarkiewicz et al., 1999, Vlasenko et al 2002,
Ivanov et al, 2005) and in the vicinity of. Snake (Smith, Mikhailova, 2008), as well as
estimates of total variance and spectra of the synoptic variability of currents off the
north-eastern coast of the Black Sea (Ovchinnikov et al, 1986, Titov, 1990, Titov and
Savin, 1997). They show that in the Caucasian Black Sea coastal zone variance synoptic
velocity variations are 1.5-2.5 times higher than the high-frequency dispersion.
Exceeding the synoptic variance in water temperature over the high reached 3-5. The
spectra of the variability allocated significant peaks at periods of 12, 8-10; 6 4.2 days.
In some ways, similar to the mentioned research ship and satellite observations of
meandering longshore Basic Black Current and vortex at its seaward and coastal flanks.
In general, these observations were made outside of the shelf zone and their results are
summarized in the book (Comprehensive Research ..., 2002) can not be uniquely
extrapolated into it. The most discussed of synoptic processes in these studies - nearly
always traceable chain of anticyclonic eddies in the coastal side of dim moving along
the coast to the northwest. Their dimensions are large longshore axis of 50-70 km, a
small cross - 20-30 km. Between two consecutive vortices varies from 2 to 14 days. In a
later study (Zatsepin et al, 2008) described the horizontal field vector currents in the
anterior (front) part of such a vortex over the continental slope according to a towed
acoustic Doppler current meters. Analyzing these results, however, it should be noted a
number of features (distinct time intervals, and apparently reversible nature of longshore
currents, synchronous reversal of the vectors on a fairly large distances along the coast
and others) who are physically much more logical to interpret the wave in terms of
CTW than with turbulent eddies in terms of shear.
Summarizing the review of the problem, we can say that the special studies of
synoptic variability of temperature and salinity in the shelf zone of the Caucasian Black
Sea, such executed by the southern coast of Crimea (Ivanov, Jankowski, 1993, Ivanov et
al, 2005), has not yet been conducted. The purpose of this article - to fill this gap by
observations at the Blue Bay in June-July, as well as archival data coastal
hydrometeorological Gelendzhik station.
Conclusions
Results of the analysis of observational data of meteorological characteristics,
temperature and salinity of water at the Blue Bay in the Russian Black Sea coast near
the town of Gelendzhik in June-July showed a very intense synoptic thermohaline
variability with time scales of several days, weeks, and 15 ˚C sweep respect to
temperature and salinity of 1,5 ‰. The most important maritime events in the synoptic
observations were upwelling of cold subsurface water and salt, and the subsequent
invasion of the surface lens of warm and brackish water, which led to the formation of a
barrier layer and heat significantly (up to 28,5 ˚ C) surface waters. In turn, this created
an unfavorable ecological situation in the bay. Both events were not unique due to local
weather conditions, the synoptic variability of which was rather weak. It is suggested
that they are largely attributable, respectively, the divergent and convergent phases of
coastal trapped waves, dynamic signs which were followed by parallel observations of
currents in the expedition of Institute of Oceanology RAS. Wind effects were only an
additional factor in certain periods of time reinforcing effect CTW. Thermohaline
characteristics of lenses of freshened waters suggest their origin from the coastal district
of Sochi. Analysis of the retrospective (archival) observations on the
hydrometeorological Gelendzhik station showed that traced in June 1999-2011, the
synoptic nature of the thermohaline variability in this region were repeatedly observed
in June last year with a close match intensity, duration and phases of individual synoptic
events. Thus, the results and findings can be considered fairly typical for the Russian
Black Sea coastal zone.
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