Modeling of the Specific Features of Climate in the Black-Sea Region

By the method of cluster analysis, we obtain a collection of meteorological fields for six typical synoptic situations in Eastern Europe for 1982–1996. We study the possibility of evaluation of the climatic characteristics of the field of precipitations for the Black-Sea region on the basis of a mesoscale atmospheric model with the use of certain statistically selected typical situations as input data.     

混响环境中声场重构的实验研究

针对混响环境非自由声场中声源测量的问题,本文以消声水池和混响水槽为实验环境,以换能器辐射的声场为研究对象,以水听器阵列为测量前端,进行了混响环境非自由声场中声源对象的测量、分析和重构的实验研究。通过单层水听器阵列对非自由声场进行声压分布测量,并对测量结果作声波分离处理,将分离前后的声压分布和在消声水池中测量的声压分布进行比较,给出了声源频率为5 000 Hz和7 000 Hz时,声场重构的误差分析结果。结果表明,基于单层水听器阵列声压测量的声波分离方法,能够较精确地对混响环境中的声场进行重构。     

台风“天秤”对两种深海声道下声传播的影响

将Argo浮标资料与卫星遥感再分析数据相结合,调用基于抛物方程算法的RAM(Range-dependent Acoustic Model)模型,研究了2012年第14号台风“天秤”对不完整深海声道(3 000 m)和完整深海声道(5 500 m)两种水深条件下声传播特性的影响。结果显示:台风对海水的影响局限于表层水体,具体为混合层加厚,混合层内温度梯度接近于零,声速在混合层内正梯度分布;混合层下方一定深度的水体增温,相应的声速也增大。声源在混合层内时,主要对海表层的声传播产生影响,两种水深条件下均出现表面波导声传播模式以及泄漏模式。声源在混合层以下时,不完整深海声道条件下台风使得会聚区向着声源方向靠近;完整深海声道条件下台风对会聚区的位置影响不明显,但声波的翻转深度增加近500 m。     

浅海声传播和混响的选频衰减

在强负跃层浅海的爆炸声实验中,发现当声源和接收器都位于跃层之上时,平均混响强度和某一航向的声传播损失在频率1000-2000Hz之间出现强烈的异常衰减现象,而且很有意思的是发射和接收均无指向性的平均混响强度的异常衰减与该航向声传播损失的异常衰减具有中心频率相同、带宽一致、附加衰减值相近的窄带共振或选频衰减特权.显然,这一异常衰减现象无法用各向异性的机理(内波、海面或海底的有规律起伏等)来解释.根据本文实验所得的传播损失和混响强度的深度结构以及一些间接的证据,我们认为这一选频附加衰减是由分散活动干跃居上部的有鳔鱼(极可能是鱼)所引起的.     

Frequency-selective attenuation of sound propagation and reverberation in shallow water

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Spectra of the Black-Sea tsunamis

We perform the analysis of the time spectra of four tsunamis generated in the Black Sea by the earthquakes of 26.07.1927, 11.09.1927, 26.12.1939, and 12.07.1966. For the analysis of the spectra, we used digitized marigrams obtained for 12 points of the Black-Sea coast. The obtained spectra are, as a rule, multimode and have 1–4 spectral maxima. One maximum corresponds to the periods typical of tsunami waves and the other maxima correspond to the oscillations of the sea level with lower frequencies. It seems likely that the events of tsunami are accompanied by low-frequency oscillations of the level caused by the atmospheric forcing, seiches, or other factors. In numerous cases, the oscillations from the predominant energy range lie outside the characteristic range of periods of the tsunami waves. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 21–30, September–October, 2007.     

Spatial modulation experiments in the underwater acoustic channel

A modulation technique for increasing the reliable data rate achievable by an underwater acoustic communication system is presented and demonstrated. The technique, termed spatial modulation, seeks to control the spatial distribution of signal energy such that the single physical ocean channel supports multiple parallel communication channels. Given a signal energy constraint, a communication architecture with access to parallel channels will have increased capacity and reliability as compared to one with access to a single channel. Results from two experiments demonstrate higher obtainable data rates and power throughput for a system employing spatial modulation than for one that does not. The demonstrated benefits were characterized by an equivalent SNR gain of over 5 dB in the first experiment. In the second experiment, using two element source and receiver arrays with apertures of 0.9 m, a coherently modulated signal was shown to offer nearly 50% greater capacity by using spatial modulation than by using temporal modulation alone.     

水下声学定位中声速改正方法的比较

介绍了水下声学定位原理以及目前常用的几种声速改正方法,提出了一种泰勒级数展开法和声线修正法组合的声速改正方法。通过模拟算例,将加权平均声速法、泰勒级数展开法、等效声速剖面法、声线修正法和组合方法进行了比较,展示声线修正法和组合方法的效果。     

Modeling of decadal variations in the Black-Sea ecosystem

We consider the decadal evolution of the Black-Sea ecosystem on the basis of a three-dimensional coupled model consisting of the Black-Sea circulation model and a biogeochemical block. The circulation model is based on the widely used POM (Princeton Ocean Model) model. The calculated hydrophysical fields are interpolated then to levels of the biogeochemical model, which covers the upper 150-m layer. We demonstrate the close relationship between the interannual variation of hydrophysical fields and the evolution of the main elements of the ecosystem. The period under consideration (1992–2001) is characterized by the warming of the Black-Sea upper layer, which can be traced by the trend of a growing surface temperature. It follows from the results of modeling that the process of warming is also revealed in the subsurface hydrophysical characteristics and the dynamics of the main elements of the Black-Sea ecosystem.     

Modeling the generation and gravity-capillary waves using an underwater sound source

This is an experimental study of the acoustic method of surface-wave excitation using an underwater source of high-frequency (950 kHz) sound. The surface waves are excited at the sound-beam modulation frequency (3–55 Hz). For a normal fall onto the free surface, the modulated sound beam efficiently generates waves in the gravity-capillary range. This provides flexible electronic control of the main wave parameters (frequency and amplitude) in the packet and continuous modes. The amplitude-frequency characteristics of the process of surface-wave generation were obtained by numerical calculations (based on equations for the rate of acoustic flux and propagation of gravity-capillary surface waves) and by experiments (based on surface wave measurements by optical and contact methods). Both values are very consistent: on the background of a similar monotonic attenuation with frequency, they have a local dip near the minimum of the phase velocity and oscillation in the frequency range above 20 Hz. The experiments on the excitation of wave packets by single acoustic messages with varying lengths and powers, as well as by falling water drops, indicated that, in all cases, the phase characteristics are satisfactorily consistent with one another and the time needed for the signal to arrive at the measurement point is determined by the group velocity.     

Climatic structure of the wind fields in the Black-Sea region

For the Black-Sea region, we perform the dynamic reanalysis of the data on atmospheric circulation for the period 1958–2001 by using the HadRM3P model with a space resolution of 25 km. We estimate the mean climatic atmospheric fields of vorticity and divergence of the wind velocity and study their space structure and seasonal variability. The climatic estimates of the annual course of vorticity of the wind velocity over the sea are presented. The obtained large annual average values of vorticity of the velocity reveal the predominant role played by the wind action in the generation not only of the seasonal variability but also of the mean cyclonic circulation of waters in the Black Sea.     

浅海声信道文本信息传输研究

论文首先介绍浅海声信道声传输的基本特性,指出在此类信道中进行多媒体信息传输的特殊困难.随后论述了文本信息传输所具有的抗噪声、抗起伏等优良性能,较能适应于水声信道的复杂性和多变性,但属于较高速率的文本信息传输,多途干扰仍然是文本信息正确检测的根本障碍.文中分析了频率跳变技术克服时域扩散较短的浅海多途的可行性和需解决的关键技术.海上获得的初步实验结果说明了文本信息传输所具有的优越性,值得今后继续深入的研究.     

Relationship between the Beam Attenuation Coefficient and the Concentration of Suspended Matter in Black-Sea Waters

By using the results of simultaneous measurements of the beam attenuation coefficient and the concentration of suspended matter in water samples, we deduce the relationships between these parameters for wavelengths of 640, 660, and 677 nm. The proposed formulas are used for the evaluation of the concentration of suspended matter according to the data of optical measurements performed in cruises of research vessels. We present two maps of the distribution of suspended matter plotted for the north part of the sea in November–December 1991 and for the south part of the sea in July 1992.     

时变多径水声信道的仿真研究

本文针对浅海水声信道的时变特性,基于射线理论引入海洋参数——强度起伏参数Φ、不均匀度参数A,建立有效的时变多径信道模型,并采用Matlab工具进行仿真．仿真结果表明,该模型相比于确定性模型更容易理解、更真实．文中给出的模型和结论能够为实际通信系统中发射接收机深度等的选择和设计提供一定的参考和依据,有助于对水声信道的了解．     

Monitoring of the Black-Sea Dynamics Based on Satellite Technologies

We present a survey of the principles and methods of satellite monitoring of the ocean, analyze the prospects of application of the data of satellite measurements to the operative diagnostics and prediction of circulation in the Black Sea, and discuss the physical foundations of remote sensing, the possibilities of contemporary equipment aimed at the observation of the sea surface from satellites, and the applicability of satellites as retransmitters of the data of measurements from free-drifting buoys. The contemporary oceanographic investigations carried out from satellites enable one to use the accumulated data for the numerical analysis of currents in seas and oceans in the model of general circulation as well as for the creation of a system of operative diagnostics and prediction of the state of marine environment. Examples of experimental realization of elements of the system of operative diagnostics of the state of the Black Sea based on the use of the satellite data are presented and the prospects of prediction of currents in the basin are analyzed.     

Specific features of the field of surface temperature in the Tropical Atlantic

On the basis of generalization of the data of many-year hydrological observations and the data of meteorological satellites accumulated in recent years, we characterize some specific features of the surface temperature in the Tropical Atlantic. The influence of solar radiation, local heat balance, and the advective and diffusion heat transfer on the temperature of the water surface is analyzed. The mechanism of formation of the thermohalocline and local sites of elevated temperature near the estuaries of large rivers (such as the Amazon, Orinoco, Mississippi, Congo, and Niger) is described. We also characterize the formation of the seasonal variability of the near-equatorial temperature maximum, equatorial temperature minimum, and equatorial divergence rate. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 28–38, November–December, 2007.     

耦合Galerkin简正波解的抛物方程方法水下声传播计算

研究水平变化的海洋环境下声传播的计算方法.把Galerkin方法的简正波解应用于耦合简正波抛物方程,可同时考虑海水和海底声场计算,对水平变化的海洋环境问题的数值计算表明,在包含海水和海底的声场计算中该方法的计算结果都具有较高的精度.     

Ice response to an underwater body moving in a frozen channel

Strains in the ice cover of a frozen channel, which are caused by a body moving under the ice at a constant speed along the channel, are studied. The channel is of rectangular cross section, the fluid in the channel is inviscid and incompressible. The ice cover is modeled by a thin viscoelastic plate clamped to the channel walls. The underwater body is modeled by a three-dimensional dipole. The intensity of the dipole is related to the speed and size of the underwater body. The problem is considered within the linear theory of hydroelasticity. For small deflections of the ice cover the velocity potential of the dipole in the channel is obtained by the method of images without account for ice deflection in the leading order. The problem of a dipole moving in the channel with rigid walls provides the hydrodynamic pressure on the upper boundary of the channel, which corresponds to the ice cover. This pressure distribution does not depend on the deflection of the ice cover in the leading approximation. The deflections of ice and the strains in the ice cover are independent of time in the coordinate system moving together with the dipole. The problem is solved numerically using the Fourier transform along the channel, the method of normal modes across the channel, and the truncation method for resulting infinite systems of linear equations. It was revealed that the strains in the ice strongly depend on the speed of the dipole with respect to the critical speeds of the hydroelastic waves propagating along the frozen channel. The width of the channel matters even it is much larger than the characteristic length of the ice cover.     

水下光学无线通信的海水信道特性研究

提出了将具有比声学高达几倍的数据通信速率,良好的安全性和隐蔽性的光学无线通信技术应用于海军、海洋科学研究和水下工程等领域,实现高速率的水下无线通信技术实现海量数据的信息交换.基于生物光学特性的水下光学信道模型,建立了水下光学通信系统性能分析方法.并对基于发光二极管(LED)的水下光学无线通信系统进行了仿真,其结果表明所建立的方法可以进行各种海域水质环境的模拟,便于时水下光学无线通信系统性能进行预测评估,为水下光学无线通信系统的设计方案的评估提供了依据.