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51.
52.
This presentation introduces a new ocean autonomous profiler for multiparametric surveys at fixed geographical locations.
The profiler moves down and up along a mooring line, which is taut vertically between a subsurface flotation and an anchor.
This observational platform carries such modern oceanographic equipment as the Nortek Aquadopp-3D current meter and the Teledyne
RDI Citadel CTD-ES probe. The profiler was successfully tested in the northeastern Black Sea during 2007–2009. By using the
profiler, new data on the layered organization of the marine environment in the waters over the upper part of the continental
slope were obtained. The temporal variability of the fine-scale structure of the acoustic backscatter at 2 MHz was interpreted
along with biooptical and chemical data. The patchy patterns of the acoustic backscatter were associated with physical and
biological processes such as the advection, propagation of submesoscale eddy, thermocline displacement, and diel migration
of zooplankton. Further applications of the multidisciplinary moored profiler technology are discussed. 相似文献
53.
A possible approach to, and preliminary results of, amplitude calibration of acoustic signals backscattered from an ADCP moored at the bottom of the near-shelf zone of the Black Sea is considered. The aim of this work is to obtain vertical profiles of acoustic scattering signal levels, showing the real characteristics of the volume content of suspended sediments in sea water in units of conventional acoustic turbidity for a given signal frequency. In this case, the assumption about the intervals of maximum acoustic transparency and vertical homogeneity of the marine environment in long-term series of ADCP measurements is used. According to this hypothesis, the intervals of the least values of acoustic backscattered signals are detected, an empirical transfer function of the ADCP reception path is constructed, and it is calibrated. Normalized sets of acoustic backscattered signals relative to a signal from a level of conventionally clear water are obtained. New features in the behavior of vertical profiles of an acoustic echo-signal are revealed due to the calibration. The results of this work will be used in subsequent analysis of the vertical and time variations in suspended sediment content in the near-shelf zone of the Black Sea. 相似文献
54.
A laboratory study of the alongshore current shear instability in a rotating and nonrotating homogeneous fluid was carried out with special attention paid to the conditions of the coherent eddy structure formation in a shear flow. The cases with both cyclonic and anticyclonic velocity shear between the current core and the coast were reproduced in a wide range of nondimensional velocity shear variations. No coherent eddy-like structure formation was observed in the nonrotating fluid; the flow was always chaotic or turbulent. However, chains of coherent eddy-like structures were formed in the rotating fluid in the case with cyclonic velocity shear in a broad range of its variations. In the case with anticyclonic velocity shear, a chain of eddies was observed only when the velocity shear was quite low. When it was high, the flow was chaotic or turbulent. A physical model that explained the asymmetry in the conditions of the coherent eddy-like structure formation in the rotating fluid with cyclonic and anticyclonic velocity shear was considered. The laboratory results agreed with the observations of coherent submesoscale eddies in the Black Sea coastal zone. 相似文献
55.