The relationship between the amplitudinal characteristics of the high-frequency spectral components of wind-generated waves and the wind velocity over the sea

The relationship between the RMS amplitudes of the wind wave spectral components and the wind speed has been studied at ten frequencies in the band of 0.65–23 Hz. To measure the parameters of the high-frequenci waves, a resistance elevation wave gauge was operated, which was deployed in the Black See on an oceanographic platform near Katsively. The correlation between the wave amplitudes and the wind velocity at high frequencies of 5–23 Hz, corresponding to gravitation-capillary ripples, was found to reach a value of 0.8. At lower frequencies of 0.65–4.3 Hz, corresponding to short gravity waves, it dropped to 0.5–0.7. The response of spectral components to the wind speed variations in the gravity-capillary range is higher than in the range of short gravity waves. The results obtained differ from Phillips' idea about a saturated range for the frequency form of the spectrum of high-frequency gravity waves, since a linear dependence of the spectral amplitudes on the wind speed is established at a wind of force 1–8.Translated by Mikhail M. Trufanov.     

Analysis of Many-Year Variations in River Runoff into the Arctic Ocean

Statistical analysis of long-term hydrological observations has shown that the interannual variations in the total river runoff into the Arctic Ocean can be considered as a stationary process. Similar are the variations in the annual runoff of the Ob, Lena, and rivers of the northwestern Asia. However, some components of the total runoff into the Arctic Ocean feature distinct and fairly complicated disturbances in the homogeneity of runoff variations. For example, variations in the annual runoff of the Yenisei River have a distinct nonmonotonic trend: the runoff systematically decreased till the late 1950s and increased since the late 1960s. The rivers of the European part of the Arctic Ocean drainage basin featured a decrease in the amplitude of variations in runoff during the past decades. Rivers of the northwestern America and northeastern Asia featured a regular increase in the amplitude of runoff variations and their autocorrelation since the late 1960s.     

Analysis of Russian Hydroacoustic Data for CTBT Monitoring

—?As part of a collaborative research program for the purpose of monitoring the Comprehensive Nuclear-Test-Ban Treaty (CTBT), we are in the process of examining and analyzing hydroacoustic data from underwater explosions conducted in the former Soviet Union. We are using these data as constraints on modeling the hydroacoustic source as a function of depth below the water surface. This is of interest to the CTBT because although even small explosions at depth generate signals easily observable at large distances, the hydroacoustic source amplitude decreases as the source approaches the surface. Consequently, explosions in the ocean will be more difficult to identify if they are on or near the ocean surface. We are particularly interested in records featuring various combinations of depths of explosion, and distances and depths of recording.¶Unique historical Russian data sets have now become available from test explosions of 100-kg TNT cast spherical charges in a shallow reservoir (87?m length, 25?m to 55?m width, and 3?m depth) with a low-velocity air-saturated layer of sand on the bottom. A number of tests were conducted with varying water level and charge depths. Pressure measurements were taken at varying depths and horizontal distances in the water. The available data include measurements of peak pressures from all explosions and digitized pressure-time histories from some of them. A reduction of peak pressure by about 60–70% is observed in these measurements for half-immersed charges as compared with deeper explosions. In addition, several peak-pressure measurements are also available from a 1957 underwater nuclear explosion (yield <10?kt and depth 30?m) in the Bay of Chernaya (Novaya Zemlya).¶The 100-kg TNT data were compared with model predictions. Shockwave modeling is based on spherical wave propagation and finite element calculations, constrained by empirical data from US underwater chemical and nuclear tests. Modeling was performed for digitized pressure-time histories from two fully-immersed explosions and one explosion of a half-immersed charge, as well as for the peak-pressure measurements from all explosions carried out in the reservoir with water level at its maximum (3?m). We found that the model predictions match the Russian data well.¶Peak-pressure measurements and pressure-time histories were simulated at 10?km distance from hypothetical 1-kt and 10-kt nuclear explosions conducted at various depths in the ocean. The ocean water was characterized by a realistic sound velocity profile featuring a velocity minimum at 700?m depth. Simulated measurements at that same depth predict at least a tenfold increase in peak pressures from explosions in the SOFAR channel as compared with very shallow explosions (e.g., ～3?m depth).¶ The observations and the modeling results were also compared with predictions calculated at the Lawrence Livermore National Laboratory using a different modeling approach. All results suggest that although the coupling is reduced for very shallow explosions, a shallow 1-kt explosion should be detectable by the IMS hydroacoustic network.     

Estimation of possible climatic changes of river runoff in the Northern Dvina River basin in the 21st century

Presented is a method of studying possible climate-driven changes of river runoff characteristics, according to which the atmosphere-ocean general circulation models are used for computing the climate system impact, whereas the response of a watershed to given disturbance is estimated using the model of runoff formation in a river basin. The study is carried out for the Northern Dvina River basin. Estimates of possible changes (relative to the reference period) by the middle and late 21st century of such water regime characteristics as mean annual and maximum water discharge, as well as mean discharge values for the spring, summer-fall and winter seasons, are presented.     

Similarity of rivers and their systems

Similarity criteria of rivers and river systems are studied. Zonal and azonal indicators of their similarity are established. The role of river system patterns in the changes of hydrographic and hydrologic characteristic of rivers in the passage from river heads to mouths is considered. The efficiency of applying fractal and indication analyses to river systems is examined. The extent and the scale effect of changes in various characteristics of the flow-channel systems are shown to depend on changes in river orders. The fractal dimension and the scale effects of their changes are correlated. A universal relationship between river orders, on the one hand, and river drainage area and river network density, on the other hand, was established. The root-mean-square error of the obtained formula, evaluated based on data on 274 watersheds, was 0.27, enabling it to be used in hydrological calculations under various landscape conditions.     

Lidar sensing of topographic inhomogeneities on the rough sea surface

The results of lidar sensing of the sea surface carried out from an oceanographic platform in the Black Sea under different hydrometeorological conditions are considered. It is found that the frequency, time, and intensity of the mirror-reflected lidar specks of light vary essentially when the wind wave structure anomalies appear, which arise owing to some physical processes evolving in the air-sea boundary layers. The effects conditioned by an unsteady and non-uniform wind, the hydrological front, the slicks related to internal waves and Langmuir circulation, industrial pollution of the sea surface by surface-active substances, and rainfall are estimated quantitatively. A conclusion about the prospects of application of the lidar specks indication method for ecological monitoring and control of the sea surface state and internal basins is drawn.Translated by Mikhail M. Trufanov.     

A computer-aided framework for subsurface identification of white shark pigment patterns

Subsurface video footage can be used as a successful identification tool for various marine organisms; however, processing of such information has proven challenging. This study tests the use of automated software to assist with photo-identification of the great white shark Carcharodon carcharias in the region of Gansbaai, on the south coast of South Africa. A subsurface photo catalogue was created from underwater video footage. Single individuals were identified by using pigmentation patterns. From this catalogue, two images of the head for each individual were inserted into automated contour-recognition software (Interactive Individual Identification System Beta Contour 3.0). One image was used to search the database, the other served as a reference image. Identification was made by means of a contour, assigned using the software to the irregular border of grey and white on the shark's head. In total, 90 different contours were processed. The output provided ranks, where the first match would be a direct identification of the individual. The method proved to be accurate, in particular for high-quality images where 88.24% and 94.12%, respectively, were identified by two independent analysts as first match, and with all individuals identified within the top 10 matches. The inclusion of metadata improved accuracy and precision, allowing identification of even low-quality images.     

Polyvariant estimation of possible climatologic river runoff changes with emphasis on the Northern Dvina catchment

Rivers of the Northern Dvina catchment are considered to demonstrate the possibility of obtaining polyvariant estimates of changes in the water regime of rivers in the northern part of the forest zone, which are caused by expected changes in air temperature and precipitation. For this purpose, the dynamic-stochastic modeling approach was applied. The snowmelt and rainfall runoff model developed at the Hydrometeorological Research Center of the Russian Federation was used as a hydrological unit. Meteorological observational data collected during the 50- to 60-year period were statistically expanded by using an approach based on composing artificial variants of the annual cycle of meteorological variables, which can be performed through combining the observed variants of weather conditions of the cold and warm periods. As a result, polyvariant estimates of possible changes in the water regime of rivers corresponding to various scenarios of changes in air temperature and precipitation were obtained.     

Fluid migration and location of fractured layers in the crystalline basement by temperature logging in the Volga Region, Russia

High-precision temperature logging in deep and superdeep wells has permitted the study of the thermal regime in the granite–gneiss layer of the Earth's crust. The long-term logging works have allowed the classification of temperature anomalies recorded in the crystalline basement. Most anomalies have been supposed to be caused by loosely aggregated, permeable zones. The classification reflects main types of processes at a great depth — such as injection, inflow and upward migration of gas-cut fluid. The results of great practical importance are obtained using our classification: some intervals — where temperature anomalies interpreted as inflow reservoirs were revealed — have produced fluid, and others interpreted as injection reservoirs absorbed borehole fluid during tests.     

Transfer function of the differential wave gauge

The transfer function of a differential wave slope meter having the form of a two-element resonance array is determined. The measured spectrum depends on the coherence of the wave field and on the differential wave gauge's measuring base. Theoretical calculations of the transfer function are supported by experimentally derived data. Some recommendations are suggested on how to conduct measurements in the field and under laboratory conditions. Measurement accuracies are compared and limits of applicability are defined for a method of measuring sea surface slope by means of the differential wavemeter. The results presented may be effectively used to perform measurements of surface and internal waves, turbulence, etc.Translated by V. Puchkin.