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Multiscale wind cycles and current pulses at the Black Sea eastern boundary Vasiliy Melnikov, Lidija Moskalenko, Vladimir Piotoukh and Andrey Zatsepin P. P. Shirshov Institute of oceanology RAS, Physical oceanography, Moscow, Russian Federation Россия, 117997, г. Москва, Нахимовский проспект, 36, тел. /факс. : +7 499 124 63 83 E-mail: [email protected] ru, [email protected] ru, [email protected] ru, [email protected] ru Abstract The goal of the research is to examine meteorological descriptive elements, sea-water properties, regional hydrodynamics and energy conversion fluxes in order to study sea responses to the local and far-field weather system. The Black Sea is situated in the chain of internal basins between the North Atlantic and Central Asia deserts in the marginal interaction zone and, accordingly, is under the influence of the Azores and Siberian anticyclones, Arctic cold-air surges and subtropical desert belt to the south. The analysis is based on the data of modern oceanographic measuring network "Hydro-physical Polygon" of the Shirshov Institute of Oceanology, using contact and remote sensing methods, weather stations around the Black Sea coasts, including long-term (1938 -2014) measurements at the Gelendzhik weather station. Various satellite and Reanalysis databases are used. Currently, there are three long-time measuring moored stations (each contains ADCP and thermistor chain) and scanning profiling system "Akvalog”/. Hydrological sections and field surveys using towed ADCP and CTD are performed on a regular basis. The data are accumulated in the coastal archive , which allows calibration of satellite measurements and testing numerical models. Data processing includes data sets preparation, editing, time series, statistical calculations using histograms, progressive vector diagrams, traditional Fourier spectral analysis including auto- and cross spectra, auto and mutual wavelet diagrams, moving spectrograms, vector data methods using rotary components, spectral invariants, empirical modes, hodograph and pre-specified spectrum representations on the basis of stochastic models with imposed dynamical assumptions. Due to the intermittent nature of the time rows, spectral representation is misleading often. In order to identify the individual evolving dynamical phenomenon, typical background (seasonal) three-dimensional structures of the hydrological field, as well as quantified anomalies, associated with different frequency components of variability, such as sub-meso-scale eddies, marginal shelf waves, inertial oscillations, diurnal, semi-diurnal and short-period internal waves, long surface waves, were estimated. Based on estimates of the statistical relationships between different parameters of hydro-meteorological system, including meteorological elements, sea level, sea temperature and flow fields, space/time scales of the observed fields variability were estimated. Several new features of the physical mechanisms of multiscale hydro-physical processes in the shelf zone of the Black Sea, have been revealed. In particular, it is shown, that there are wind self-similar cycles at different time scales, each cycle being consisted of a pair of northeast and then southeast winds, which corresponds to the alternative influences of the Azores and Siberian highs(in winter). In the range of decadal (10 years) scale and in macro space view, long-term wind cycles support basic Black Sea circulation(Rim Current). Wind cycles with a time scale of about 20 days give rise to distinct upwellings, appeared with the same frequency. Along with each upwelling, radical hydrological restructuring of the stratification is accompanied by intense advection with high velocities(up to 1 m/s). Kinetic energy is dominated by alongshore currents, the direction being reversed periodically. The vertical structure of currents is rather complicated. When the current speed exceeds some threshold value, the flow gives rise to relaxation oscillations with a period of about 24 hours with counterclockwise velocity vector rotation. All the above mentioned events and current pulses cause significant variations of air-sea fluxes. Region Scope of work The objectives are to estimate spatial and temporal scales of regional hydrometeorological fields in order to clarify winds and currents variabiliity and interactions in a broad band of timescales in the atmosphere-sea "Hydro. Polygon“ system in the Black Sea. Multi-scale hydrophysical phenomena Data A The analysis is based on measurements using variouse hydrophysical probes, standard meteorological 134 coastal weather stations data (from the list of WMO network) around the entire Black Sea coasts in the period 1998 -2014, as well as meteostations in some regions of the Northern Hemisphere (www. meteoinfospace. ru), including long(19382014) time series of the Gelendzhik meteorological station. Databases NCEP-NCAR, Sciron, Quick. SCAT and Path. Finder v 5. were used Data processing To visualize time series vector quantities (direction and velocity of wind and currents) progressive vector diagrams were plotted. Variabilty of parameters at different time scales were obtained by means of different filters with control of filter effects using autospectra. Statistical correlations were assessed by conventional correlation, spectral and wavelet analysis. Brief review Bottom topography and orography in the vicinity of the Black and Azov Seas. Scale of heights and depths, in meters, the resolution of the space -1 minute, Data from: Smith, W. H. F. and D. T. Sandwell (1997), Global seafloor topography from satellite altimetry and ship depth soundings, Science, v. 277, 1957 -1962. 1. Hydro. Polygon measurements system. 2. Intercalibrations. 3. Meteorological variations features. -multy-scale wind cycles over the Black Sea. -prevailing winds and typical atmospheric barometric fields. 4. Main frequency constituents of meteorological and hydrophysical variability. -probability and spectral characteristics. Wavelet diagrams structure. -climatic trends. 5. Kinetic energy and air-sea flows. 6. Upwellings. -seasonal winds and sea surface temperature. -upwelling occurrence. - upwellings and winds. Sea surface geostrophic circulation of water relative to a pressure level of 500 d. B (25. 06 -06. 07 1996). ОЧТ - Rim Current; ЦМ - cyclonic meander; ПАВ- coastal anticyclonic eddy; ЦВ cyclonic eddy; БАВ - Batumi anticyclonic gyre. A Fragments (15 km-20 km) of images obtained by radar ASAR satellite Envisat, showing the spiral small-scale eddies, typical for warm season: a - two cyclonic eddies with diameters of 3. 75 km (A) and 3 km (B); b - a cyclonic vortex with diameter of 3. 5 km (C); в - cyclonic eddy with a diameter of 2. 5 km (D); r - cyclonic eddy with diameter of 5. 3 km (E). A B C D Hydrophysical Polygon in the north-east part of the Black Sea. Measurements sites. Notations: 1)red star–Shirshov Institute pier (Blue Bay, 44. 58 N, 37. 98 E); 2)red square - Gelendzhik meteostation (44. 55 N, 38. 05 E); 3)green dots– satellite temperature data(1985 -2011), nightly SST, AVHRR, NOAA; 4)pink squares. Black Sea SLA(sea level anomaly), AVISO products. Fuzzy blue lines-bottom topography isolines; orange lines-Earth surface orography (without heights); red dashed lines separate three polygons under analysis. точки-ряды аномалий уровня моря (Black Sea MSLA, AVISO products). B Black Sea multi-scale wind cycles and climatic trends Progressive vector diagrams of winds around the Black Sea coasts on the basis of coastal weather stations (WMO network) data in the period 1998 -2011. Distance scale for diagrams is 1 unit of scale = thousand km. Small green circles denote years. Bigger red circle - weather-station location. A –Upwellings evolution: sea level (H-430 cm) - 1; SST ( C) - 2; wind gust speed (m/s) - 3; wind speed (m/s) - 4; wind direction Azimuth (grad. /100) - 5, during the development of strong upwelling on August 1, September 1 and September 28, 2008, B-average sea surface temperature at weather stations in Gelendzhik in the period 2007 to 2010. Vvelocity field in the coastal-shelf zone in the region of Gelendzhik according ADCP surveys of 27 -30. 09 (A, B, C, D). The dotted line denotes the position of the alleged submesoscale anticyclonic eddies A 1 and A 2, as well as cyclonic vortex C 1. -2 Fourier and wavelet spectra comparison ( temperature fluctuations). • Spectral density (Fourier), normalized to the dispersion of the series: • 1. gray - air temperature, meteostation Gelendzhik, dt=3 hr. • 2. pink - model time series fluctuations in air temperature. • 3. green -temperature of water, semi-diurnal, meteostation Gelendzhik. • 4. brown - index NAO (1853 -2012, monthly. ) • 5. blue - Wolf numbers, (1640 -2012, decadal 10 d. ). Typical seasonal wind cycles (Elementary cycle- EC). Typical cycles of dominant winds direction change. Pair of NE and SE- winds form a cycle, appeared repeatedly at differen t time scales. The self-similarity of wind direction variations is due to the repeatability in the development of pressure regional structures. Wind seasons are distinguished by the prevailing wind direction: Winter - December to February; Spring - March; second Spring-April to June; Summer - from July to October; Autumn – November. A Conclusions B Main constituents of implicit air heat flow. From paper^ FOTIS PANAGIOTOPOULOS AND MARIA SHAHGEDANOVA. Observed Trends and Teleconnections of the Siberian High: A Recently Declining Center of Action. JOURNAL OF CLIMATE, VOLUME 18, MAY, 2005, pp. 1411 - 1422. C D A- first phase of the EC(SE wind); B - second phase of the EC (the transitional period of weak winds in different directions), C - the third phase of the EC (NE winds), and D - transition period breeze fluctuations. Wavelet-diagram of horizontal kinetic energy of currents in the upper layer in vicinity of the Blue Bay, near Gelendzhik. Winter (DJF) SLP averaged over 1900– 2001 using the Trenberth and Paolino (1980) gridded SLP dataset. Isobars are spaced every 3 h. Pa with solid contours used for SLP values greater or equal than 1015 h. Pa and dashed lines used for lower values. The area enclosed by the bold line shows the region over which SLP has been averaged to calculate the SH index (40°– 65°N, 80°– 120°E), 1. On the basis of the in-situ measurement information of the "Black Sea hydrophysical polygon" (Shirshov Institute of Oceanology, RAS), using remote sensing and different reanalysis data, the hydrometeorological system in the shelf-slope zone of the north-east part of the Black Sea is under investigation, including regional hydrodynamics, water transport and energy transformation processes due to the atmosphere-sea interactions. 2. Typical feature of the regional climate system is the cyclic transitions of wind from north-east direction to south-east and vice-versa (“Elementary cycle” (EC)). There are self-similar wind cycles at several time scales, each cycle being consisted of the same combination of north-east and south-east winds, which corresponds to alternative influences of the Azores and Siberian anticyclones. 3. Resemblance of wind variations temporal structure for the EC of different scales is viewed as fractal variability of wind associated with the recurrence of the NE and SE types of synoptic atmospheric processes, prevailing in the region of the North Caucasian coast. 4. As follows from the progressive vector diagrams at weather-stations around the Black Sea coasts, climatic winds form a cyclonic gyre with the center approximately over Turkey. In the long-term (years) and in the macro view such cycles support Basic Black Sea Circulation(Rim Current). 5. Several long-term “Elementary cycles” constitute climatic "wave" of annual wind direction variations from average South-East wind to the average North-East wind. 6. Meridional component of wind velocity in the climatic wave, as well as the accompanying variations in air and water temperatures, are associated with the baric dipole EAWR. NAO influence is manifested in changes of zonal air transport. At the climatic time scale, South-East winds are revealed for the winter seasons, which has been related to the SA flank influence. In summers, climatic winds are predominantly North-East due to the persistent effect of Azores baric ridge. 7. Bringing more air from the south to the north corresponds to the negative EAWR. phase. Accordingly, interannual air and water temperatures are increasing with the increase in the positive (from south to north) meridional air transport 8. Typical winds give rise to a number of sea dynamic processes. of wide-range spatial and time scales. Wind cycles with a time scale of about 20 days give rise to distinct upwellings, appeared with the same frequency. Each upwelling causes significant variations in fluxes of momentum, sensible and latent heat, buoyancy. 9. Associated with upwelling radical restructuring of the stratification is accompanied by intense advection of water at high speeds (up to 1 m / s). 10. Kinetic energy is dominated by alongshore currents, the direction being reversed periodically. The vertical structure of currents is rather complicated. . Characteristic layers can be traced. 11. When the current speed exceeds some threshold value, the flow gives rise to relaxation oscillations with a period of about 24 hours with counterclockwise velocity vector rotation. 12. All the above mentioned events and current pulses cause significant variations of air-sea fluxes. Acknowledgements This research was jointly supported by Ministry of Education of the RF (Agreement. 14. 604. 21. 0044), Russian Academy of Sciences(Program No 23), RFBR grant 14 -05 -00159, contract No 10/2013 RGS-RFBR. Publications Schematic view of upper troposhere atmospertic circulation anomalies in NCP(North. Caspian Pattern ) or EAWR (East Atlantic- West Russia) baric permanent structure. From paper: : Kutiel, H. , Benaroch, Y. , 2002. North Sea-Caspian Pattern (NCP) — an upper level atmospheric teleconnection affecting the Eastern Mediterranean: identification and definition. Theor. Appl. Climatol. v. 71, 17– 28. In summer, sea surface temperature (in contrast to air temperature) declines to averaged 23. 2 C diring North-east winds, while mean temperature for the South winds is 25. 0 C. Evolution of horizontall kinetic energy, principal currents components, progressive vector diagram, spectra during relaxation event, in the upper layer in vicinity of the Blue Bay, near Gelendzhik. 1. Melnikov V. A. Spectral evidences of self-simularity in the geophysical hydrodynamic type systems. Proceedings of XXIII International conference “Lasers. Measurements. Information. 2013", Polytechnic University Publishing , St. Petersburg, v. 3, 2013 , pp. 191 -203. (in Russian). 2. Krivoscheya V. G, Moskalenko L. V. , Melnikov V. A. , Skirta A. Y. Influence of wind regime and thermal variability on the structure and dynamics of seawater in the north-east part of the Black Sea. Akademizdattsentr, "Nauka" RAS , Oceanology, v. 52, № 4, 2012, pp. 484 -498. 3. Melnikov V. A. , Moskalenko L. V. and Kuzevanova N. I. "Black Sea Multi-Scale Wind Cycles and Climatic Trends", 3 rd Bi-annual Black Sea Scientific Conference Abstracts, Odessa, Ukraine, 31 st October - 4 th November, 2011. 4. Melnikov V. A. , Moskalenko L. V. , Golenko N. N. , and Golenko M. N. . Boreal Atmospheric circulation patterns on the basis of the world network weather station data. Geophysical Research Abstracts, Vol. 14, EGU General Assembly 2012, Vienna, Austria, EGU 2012 -13175. 5. Melnikov V. A. , Moskalenko L. V. and Kuzevanova N. I. Multiscale variations of meteorological elements. International Conference dedicated to the memory of Academician AM Obukhov “Turbulence, Dynamics of the atmosphere and climate“ , 13 -16 May 2013, Proceedings, M. : GEOS, 2013, 247 p.