Statistical characteristics of cyclones and anticyclones over the Black Sea in the second half of the 20th century

By using the NCEP reanalysis data for 1952–2000, we estimate the parameters of cyclones and anticyclones in the Black-Sea region and evaluate the statistical characteristics of their variability for each season. It is shown that the frequency of cyclones decreases in all seasons (except summer) as a result of the intensification of the North Atlantic Oscillation in the 1960–90s and the displacement of the predominant paths of synoptic disturbances to the north. For anticyclones, we reveal the opposite trend. The parameters of cyclones and anticyclones are characterized by quasiperiodic variations on the subdecadal scale also induced by the North Atlantic Oscillation. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 47–58, November–December, 2007.     

Low-frequency variations of the characteristics of pycnocline in the North Atlantic and their correlation with the North-Atlantic oscillation

On the basis of processing of the oceanographic data accumulated for the water area of the North Atlantic in 1950–1999 (∼500,000 stations), we study seasonal and interannual variations of the principal characteristics of pycnocline within the range of σ_t = 25.5–27.5 conventional density units. It is shown that the interannual oscillations of these characteristics in the entire analyzed layer can be regarded as a superposition of fluctuations with periods from 2–3 to 10–12 yr. The typical ranges of these fluctuations for the depths of occurrence of isopycnic surfaces and the corresponding temperature and salinity are equal to 20–25 m, 1–1.5°C, and 0.25‰, respectively. The intensification of atmospheric circulation at middle latitudes is accompanied by the simultaneous deepening of the pycnocline and its heating in the central part of the North Subtropical Anticyclonic Gyre. At the same time, the process of weakening of the atmospheric circulation leads to the rise of the pycnocline and its cooling. The complete cycle of interaction of the North-Atlantic Oscillation with the anomalies of isopycnic characteristics (with regard for the period of their advection) is equal to ∼6–8 yr. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 29–48, March–April, 2007.     

Satellite monitoring of wildfires during the anomalous heat wave of 2010 in Russia

We describe the specific features of the summer 2010 emergency conditions in the European part of the Russian Federation, when an anomalous heat wave (the monthly mean temperatures in the summer months were 5–9°C higher than those for 2002–2009) and prolonged blocking anticyclones led to large wildfires. We analyze their causes and consequences. The features of the satellite system for operational fire monitoring (constructed at the Aerospace Scientific Center) and examples of its application in summer 2010 are presented. On the basis of the results of processing of satellite images of low (250–1000 m), medium (∼30–50 m), and high (∼6 m) resolutions, we found that the total area covered by fire from March to November of 2010 amounted to approximately 10.9 million hectares for the entire territory of the country and and 2.2 million hectares for its European part. Daily histograms of areas covered by fire in the summer months of 2010 were constructed. On the basis of these data and empirical models, we estimate the daily emissions of carbon monoxide (CO) from wildfires in the summer months of 2010 for the European part of Russia and Moscow oblast. On some days in August 2010, these emissions reached 15000–27000 t for the European part of Russia and 3000–7500 t for Moscow oblast. On the basis of analysis of data from the AIRS spectrometer (Aqua satellite), we derived the spatial distribution of CO concentrations at heights of 2 to 10 km above the territory of the Eastern and Central Europe. Moscow was shown to have been most severely affected by smoke from wildfires occurring on August 6–9, 2010, when the concentrations of harmful gases (CO₂, CO, CH₄, and O₃) and aerosols in the air significantly exceeded both the daily and the one-hour maximum allowable concentrations.     

Estimation of the long-term variability of hydrophysical characteristics of the Black Sea based on the assimilation of the climatic hydrological fields L and altimetry data

To study the long-term variability of the thermohaline and dynamic characteristics of the Black Sea, we use three versions of climatic fields, namely, the fields reconstructed in the model according to the old (1903–1982) and new (1903–2003) hydrological climatic data arrays of temperature and salinity and according to the data of satellite altimetry. The analysis of the altimetry-based climatic fields confirms the distinctions (established earlier according to the old and new data arrays) in the seasonal variability of the integral characteristics of temperature and salinity and in the structures of hydrophysical fields in the sea. It is shown that, in the winter-spring season, the thermohaline fields reconstructed according to the new and altimetry data arrays are characterized by a small elevation of the halocline (pycnocline) and the upper boundary of the cold intermediate layer. In all seasons, the altimetry-based surface geostrophic currents contain numerous mesoscale eddies with different signs of rotation. Moreover, in all seasons, the Rim Current reconstructed according to the altimetry data is characterized by a narrower jet almost along the entire its length. This jet is especially intense near the coasts of West Anatolia. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 3–17, July–August, 2006.     

On the formation of atmospheric seasonal precipitation in the Black Sea region

The climatic features of the formation of precipitation and their correlation with the baric situation in the Atlantic-European sector are studied on the basis of the data of the Sevastopol and Feodosiya coastal hydrometeorological stations. As the source data, we use the data arrays of daily precipitation at these stations in 1900–2005 and the data of reanalysis of the fields of atmospheric pressure in the Atlantic-European sector. The comparative statistical analysis of daily precipitation for the wet and dry summer and winter seasons and the estimates of extremely high levels of precipitation for the specified periods of repeatability are presented. The existence of the dependence of occurrence of wet and dry winter seasons in Sevastopol and Feodosiya on the large-scale baric fields in the Atlantic-European sector is confirmed. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 43–51, July–August, 2008.     

The effect of seasonal and inter-annual variability of river run-off on the salinity of coastal waters in the north-western Black Sea

The paper considers the correlation between the variability of river discharges in the northwestern Black Sea and water salinity (from 1962 to 1994). As the most complete series, we have chosen salinity data collected at the port of Odessa. The dominant oscillations in the intra-annual variability of river discharges (Danube, Dniester, Dnieper, Yuzhny Bug) and salinity attain about 2–3 months and one year, respectively. In the inter-annual variability of river discharges and water salinity, cyclicities equal to about 4–6 months and 9–12 years, respectively, have been identified. Through analysing the inter-annual variations, an inversely proportional dependence has been found between the overall river discharges and salinity (between discharges in April and salinities in May, the correlation coefficient has amounted to −0.61). For each river, we have obtained the following dependences: for Odessa-Dniester, −0.72; and for Odessa-Danube, −0.65. Translated by Vladimir A. Puchkin.     

Long-term trends in the variability of deep-water thermohaline characteristics of the Black Sea

By using the archival hydrological data for 1955–1998, we analyze the trends of deep-water thermohaline characteristics of the Black Sea and their interannual and decadal variability. It was discovered that the level of salinity increased at depths greater than 1000 m in the west part of the sea from the mid-1950-s till the early 1980s and the opposite trend was observed for the next 15–20 yr. The average rate of increase in the deep-water salinity between 1960 and 1980 and its decrease after 1980 was equal to 0.05‰ per 20 yr. These facts demonstrate that the water exchange through Bosporus was intensified for the first 25 yr of the analyzed period and weakened for the next 20 yr. The interannual variability with a typical period of 6.5 yr and a quasi-20-yr periodicity are detected against the background of the parabolic trend. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 18–30, July–August, 2006.     

Investigation of the Dependence of the Space Structure and Phase Characteristics of the First-Mode Internal Waves in the Atlantic Ocean on the Hydrological Conditions

By using the linear theory of internal waves in a continuously stratified ideal incompressible liquid of finite depth and hydrological data, we study the dispersion properties and space structure of the vertical velocity of the first mode of free internal waves in the Atlantic Ocean. The dependence of the characteristics of waves on the hydrological structure of waters is analyzed. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 3–10, July–August, 2005.     

An Interpretation of the Seafloor Spreading History of the West Enderby Basin between Initial Breakup of Gondwana and Anomaly C34

The seafloor spreading evolution in the Southern Indian Ocean is key to understanding the initial breakup of Gondwana. We summarize the structural lineaments deduced from the GEOSAT 10 Hz sampled raw altimetry data as well as satellite derived gravity anomaly map and the magnetic anomaly lineation trends from vector magnetic anomalies in the West Enderby Basin, the Southern Indian Ocean. The gravity anomaly maps by both Sandwell and Smith 1997, J. Geophys. Res. 102, 10039–10054 and 10 Hz raw altimeter data show almost the same general trends. However, curved structural trends, which turn from NNW–SSE in the south to NNE–SSW in the north, are detected only from gravity anomaly maps by 10 Hz raw altimeter data just to the east of Gunnerus Ridge. NNE–SSW structural trends and magnetic anomaly lineation trends that are perpendicular to them are observed between the Gunnerus Ridge and the Conrad Rise. To the west of Gunnerus Ridge, structural elements trend NNE–SSW and magnetic polarity changes are normal to them. In contrast, almost NNW–SSE structural trends and ENE–WSW magnetic polarity reversal strikes are dominant to the east of Gunnerus Ridge. Curved structural trends, which turn from WNW–ESE direction in the south to NNE–SSW direction in the west, and magnetic polarity reversal strikes that are almost perpendicular to them are observed just south of Conrad Rise. The magnetic polarity reversals may be parts of the Mesozoic magnetic anomaly sequence that formed along side of the structural lineaments before the long Cretaceous normal polarity superchron. Curved structural trends, detected only from gravity anomaly maps by 10 Hz raw altimeter data, most likely indicate slight changes in spreading direction from an initial NNW–SSE direction to NNE–SSW. Our results also suggest that these curved structural trends are fracture zones that formed during initial breakup of Gondwana.     

Climatic and hydrophysical conditions of the development of hypoxia in waters of the northwest shelf of the Black Sea

The data of meteorological and oceanographic observations on the northwest shelf of the Black Sea for 1973–2000 are used to compute the characteristics of the entire area in the presence of hypoxia of waters under the pycnocline in the summer–autumn period and the area of surface waters with a level of salinity lower than 17.5‰ in May. The time of onset of the spring warming of air (stable transition through a temperature of 5°) is determined. A statistically significant positive trend of the air temperature (0.8° per 100 yr) is revealed in Odessa. The process of warming was observed mainly for the winter (1.5° per 100 yr) and spring (0.8° per 100 yr) periods and became especially intense since the beginning of the 1990s. On the basis of the data of correlation analyses, we establish a statistically significant relationship between the large-scale atmospheric processes [the index of North Atlantic Oscillation (NAO) and the wind conditions], the area of surface waters whose salinity is lower than 17.5‰, and the total area with hypoxia in the summer–autumn periods. For positive mean values of the NAO index (in January–March), we most often observe early spring with elevated repetition of the south and west winds with subsequent development of hypoxia in large areas of the northwest shelf. We propose an empirical regression model for the prediction of the total area of summer–autumn hypoxia of waters with predictors: the onset of the spring warming of air and the area of propagation of waters whose salinity is lower than 17.5‰ in May. The maximum error of prediction of the area with hypoxia does not exceed 5.5 ⋅ 10³ km², i.e., less than 2% of the total area of the northwest shelf in the Black Sea (to the north of 45°N).     

Structure of the Basin and Ridge System West of New Caledonia (Southwest Pacific): A Synthesis

Complementary to previous work mainly based on seismic interpretation, our compilation of geophysical data (multibeam bathymetry, gravity, magnetic and seismic) acquired within the framework of the ZoNéCo (ongoing since 1993) and FAUST (1998–2001) programs enables us to improve the knowledge of the New Caledonia Basin, Fairway Basin and Fairway Ridge, located within the Southwest Pacific region. The structural synthesis map obtained from geophysical data interpretation allows definition of the deep structure, nature and formation of the Fairway and New Caledonia Basins. Development of the Fairway Basin took place during the Late Cretaceous (95–65 Ma) by continental stretching. This perched basin forms the western margin of the New Caledonia Basin. A newly identified major SW–NE boundary fault zone separates northern NW–SE trending segments of the two basins from southern N–S trending segments. This crustal-scale fault lineament, that we interpret to be related to Cretaceous-early Cainozoic Tasman Sea spreading, separates the NW–SE thinned-continental and N–S oceanic segments of the New Caledonia Basin. We can thus propose the following pattern for the formation of the study area. The end of continental stretching within the Fairway and West Caledonia Basins ( 65–62 Ma) is interpreted as contemporaneous with the onset of emplacement of oceanic crust within the New Caledonia Basin’s central segment. Spreading occurred during the Paleocene (62–56 Ma), and isolated the Gondwanaland block to the west from the Norfolk block to the east. Finally, our geophysical synthesis enables us to extend the structural Fairway Basin down to the structural Taranaki Basin, with the structural New Caledonia Basin lying east of the Fairway Basin and ending further north than previously thought, within the Reinga Basin northwest of New Zealand.     

Evaluation of the meridional heat transport in the Subtropical Atlantic

By using the data of a standard section made along 24.5°N in the Subtropical Atlantic within the framework of the World-Ocean-Circulation Experiment, we compute the meridional heat transport. In agreement with the major part of published estimates obtained according to the data of direct oceanographic measurements, it is approximately equal to 1.1 PW. The meridional heat transport along 24.5°N is caused mainly by the quasistationary meridional circulation with fairly stable structure. At the same time, we discovered the intense seasonal variability of some components of the meridional heat transport. The contribution of eddy heat flows to the integral transport is insignificant. Dedicated to the jubilee of Prof. Viktorina Fedorovna Sukhovei __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 3–15, January–February, 2006.     

On the wind conditions of a shallow as a factor of the formation of satellite images of the Sea (Using the example of the South Caspian Sea)

Based on the scatterometer QuickScat wind data and the water-leaving radiances from the ocean color scanner SeaWiFS data for 2000–2004, we composed a pair of mean annual images of a testing site in the South Caspian Sea under conditions of west-bound and east-bound winds corresponding to the offset and onset state of the shallows in the east of the testing site. It was established that both the “offset” and “onset” radiances grow shorewards, but the former becomes about twice as large as the latter in the middle of the shallows with 10–15 m of water, while their difference tends to zero at the seaward and coastal boundaries of the shallow. These and other findings are hypothetically attributable to the inclination of the sea floor of the shallows, due to which the surfacing of bottom sediments resuspended by the drift current takes less time under the “offset” wind conditions than under the “onset” ones. The study’s results indicate that the effect of the bottom sediments resuspension upon the structure of the images of the marine shallows is universal in character and needs to be taken into account to improve the bio-optical algorithms for estimating the admixtures in the thickness of the shallows from the satellite data.     

Temporal and spatial variabilities of Japan Sea surface temperature and atmospheric forcings

In this study, we used the National Centers for Environmental Prediction monthly sea surface temperature (SST) and surface air temperature (SAT) data during 1982–1994 and the National Center for Atmospheric Research surface wind stress curl data during 1982–1989 to investigate the Japan Sea SST temporal and spatial variabilities and their relations to atmospheric forcing. First, we found an asymmetry in the correlation coefficients between SST and wind stress curl, which implies that the SST variability at the scales of the order of one month is largely due to atmospheric forcing. Second, we performed three analyses on the data fields: annual mean, composite analysis to obtain the monthly anomaly relative to the annual mean, and empirical orthogonal function (EOF) analysis on the residue data relative to the summation of the annual mean and the monthly anomaly. The first EOF mode of SST accounts for 59.9% of the variance and represents the Subpolar Front. The temporal variation of the first EOF mode implies that the deep Japan Sea could be cooler in cold seasons (November–April) of 1984–1987. Third, we computed cross-correlation coefficients among various principal components and found that the atmospheric warming/cooling is the key factor causing intra-seasonal and interannual SST variabilities.     

Experimental estimation of the coefficient of vertical turbulent exchange in a stratified layer of the black sea near the continental slope

On the basis of the data of field measurements, we present the results of numerical analysis of the intensity of vertical turbulent exchange in stratified layers of the Black Sea in the region of the shelf–continental-slope boundary depending on the local stratification. The experiments were carried out within the framework of the GEF/BSERP and Black Sea-2004 international projects. The data were obtained by using a probing version of the Sigma-1 measuring complex. In processing the data of measurements, we apply a procedure of evaluation of the coefficient of vertical turbulent diffusion depending on the external conditions based on the analysis of the spectra of the gradient of temperature fluctuations. For the two studied regions of the shelf, the coefficients of turbulent exchange turn out to be much higher (by about an order of magnitude) than for the open sea under similar conditions. This can be explained by the specific features of the bottom topography affecting the dynamics of quasiinertial waves playing to role of the main causes of small-scale mixing and vertical diffusion. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 14–24, November–December, 2008.     

Large-Scale Structure of Thermal Fronts in the East Part of the Tropical Atlantic and Their Seasonal Variability

On the basis of the climatic array of hydrological annual and monthly average data on temperature and the data of satellite observations of the surface temperature of the ocean, we refine the annual average structure of the temperature fronts and study their seasonal variability in the east part of the Tropical Atlantic in the meridional sections made along 30, 20, and 10°W, 0°, and 10°E. It is shown that the maximum intensity and seasonal variations are typical of the North Subequatorial and South Tropical Fronts varying with predominant annual period. We revealed a delay of 2–3 months in the attainment of the maximum intensity of the South Tropical and South Subequatorial Fronts in the west-east direction. Various mechanisms specifying the seasonal variability of the surface and subsurface North and South Subequatorial Fronts are discussed. There exists good agreement between the specific features of the seasonal variability of characteristics of the fronts established according to the hydrological and satellite data. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 46–59, March–April, 2005.     

Variability of Upper Ocean Heat Balance in the Shikoku Basin during the Ocean Mixed Layer Experiment (OMLET)

The heat balance of the surface layer in the vicinity of the former Ocean Weather Station “Tango” (OWS-T; 29°N, 135°E), where a large amount of heat is transported by the Kuroshio and transferred to the atmosphere, was studied by during Ocean Mixed Layer Experiment (OMLET) as an oceanographic component of the Japanese World Climate Research Program (1987–1991). Temperature and velocity in the upper ocean measured using a surface moored buoy system deployed by the Ocean Research Institute, the University of Tokyo, in total 668 days of four time series namely the periods of April 1988–November 1988 (OMELET-88), August 1989–February 1990 (OMLET-89), April 1990–September 1990 (OMLET-901) and September 1990–January 1991 (OMLET-902). We have analyzed the moored buoy data of the upper 100 m for the latter three time series (OMLET-89, -901 and -902) and here we discuss the heat balance of the upper 100 m, in combination with surface heat flux and oceanographic data provided by the Japan Meteorological Agency. A large fluctuation of oceanic heat convergence/divergence of 200–300 W/m² in amplitude with predominant period of 20–30 days occurred in the first half of OMLET-89 period, which was just the early stage in the formation process of a large meander path of the Kuroshio. A large amount of heat convergence of 71 and 79 W/m² on average was detected in observation period of OMLET-89 and -901, respectively. During OMLET-902, relatively small heat convergence of 13 W/m² was obtained. It is suggested that these variations of oceanic heat convergence in this region were closely related to the fluctuation of the Kuroshio axis to the south of Japan. This revised version was published online in July 2006 with corrections to the Cover Date.     

Seasonal freshening and salinization of waters in the Karkinit Bay

On the basis on the experimental hydrological data accumulated in the database of the Marine Hydrophysical Institute of the Ukrainian National Academy of Sciences and the meteorological data of the Marine Department of the Ukrainian Scientific-Research Hydrometeorological Institute, we study the characteristics of seasonal variability of the processes of renewal, freshening, and salinization of waters in the Karkinit Bay. We analyze and estimate the repeatability of the inflows of salt and freshened waters from the sea as well as the variations of the areas occupied by these waters in the water area of the bay depending on the seasonal and wind conditions. For the spring-summer period, we estimate the period of renewal of waters in the upper layer of the main part of the bay (11–14 days). A time interval of possible absence of noticeable water exchange between the main and east shallow parts of the bay (of about two months) is revealed in the summer-autumn period. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 24–39, July–August, 2007.     

Horizontal structure of the temperature field of the upper layer in the northwest part of the Tropical Atlantic

By using the data of observations over the spatial variability of the temperature field in the northwest part of the Tropical Atlantic carried out in a test range 400 × 400 miles in size with a horizontal resolution Δx ≈ 2 km and a vertical resolution Δ_z ≈ 0.5 m, we recorded quasiperiodic fluctuations of temperature with semidiurnal period in the subsurface layer. The internal baroclinic waves with the same period generated, most likely, on the northeast shelf of South America and propagating to the northeast are detected in the seasonal thermocline. The vertical fine structure of the temperature field has different intensities in the test range. The maximum levels of dispersions of temperature fluctuations are recorded on the boundary of the North Equatorial Countercurrent and the North Equatorial Current. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 44–52, November–December, 2006.     

Seismic stratigraphy of the quaternary Yellow River delta,Bohai Sea,eastern China

The upper 40 m of stratigraphy of the Yellow River (Huang He) subaqueous delta has been well documented, but the nature of the underlying strata is currently unknown at high-resolution. To address this deficiency we used a Geopulse seismic system to image shallow sedimentary deposits up to 120 m deep on the Yellow River delta. High-resolution seismic reflection images were processed with a series of specific techniques (e.g. swelling attenuation, dynamic s/n filter; f-x deconvolution, predictive deconvolution dipscan stack), and used with borehole data to investigate the Quaternary offshore sequences in the Yellow River (Huang He) delta. Repetitive sequences were observed and interpreted as containing layers of transgressive and regressive deposits. Six seismic transgressive and regressive cycles are identified. Unit M₆F–C₆F correlates with a relative sea-level rise (173–157 ka) and fall (231–173 ka), while Unit M₅F–C₅F is associated with a relative sea-level rise (124–100 ka) and fall (157–124 ka). Unit M₄F–C₄F spans a period of sea-level fall at 100–87 ka, followed by a rise at 87–76 ka. Unit M₃F–C₃F is a transgressive–regressive cycle dated as 76–58 ka. Unit M₂F–C₂F correlates with relative sea level fall at 58.2–36 ka and subsequent rise at 36–22 ka. Unit M₁F–C₁F was deposited during relative sea level fall (22–18 ka), followed by a rise, especially since 8.5 ka.