Automatic Identification of Internal Wave Characteristics Affecting Bathymetric Measurement Based on Multibeam Echosounder Water Column Data Analysis

The accuracy of multibeam echosounder bathymetric measurement depends on the accuracy of the data of the sound speed layers within the water column. This is necessary for the correct modeling of ray bending. It is assumed that the sound speed layers are horizontal and static, according to the sound speed profile traditionally used in the depth calculation. In fact, the boundaries between varying water masses can be curved and oscillate. It is difficult to assess the parameters of these movements based on the sparse sampling of sound velocity profiles (SVP) collected through a survey; thus, alternative or augmented methods are needed to obtain information about water mass stratification for the time of a particular ping or a series of pings. The process of water column data collection and analysis is presented in this paper. The proposed method updates the sound speed profile by the automated detection of varying water mass boundaries, giving the option to adjust the SVP for each beam separately. This can increase the overall accuracy of a bathymetric survey and provide additional oceanographic data about the study area.

Analysis of Characteristics and Turbulent Mixing of Seawater Mass in Lombok Strait

The Lombok Strait, as one of the outlet straits, is part of the ITF route, which is directly adjacent to the Indian Ocean. There is a sill in the Lombok Strait, which is a place for internal wave generation. Leg-1 data from the Japan Agency for Marine-Earth Science and Technology in collaboration with the Agency for the Assessment and Application of Technology which is part of the Tropical Ocean Climate Study Expedition including CTD Yoyo and ADCP taken using ship vehicles R/V Kaiyo. CTD Snapshot from PUSHIDROSAL using the KRI Spica 934 vehicle part of the Opssurta Baruna Jaya 2 Expedition. Determination of seawater mass stratification with the criteria for the thermocline layer is ≥ 0.05 °C.m-1. Four types of water masses were identified, Java Sea, mixed seawater mass (Java Sea - ITF) which occurred diapycnal mixing, North Pacific Subtropical Water (NPSW) and North Pacific Intermediate Water (NPIW). The seawater mass stratification in the Lombok Strait based on temperature, salinity and density which are seen to follow the internal tidal pattern. The average values for energy dissipation and vertical diffusivity for each layer and replication were 5.73 x 10-7 W.Kg-1 and 3.67 x 10-2 m2.s-1 for CTD Yoyo and 2.25 x 10-6 W.Kg-1 and 7.38 x 10-2 m2.s-1 for CTD Snapshot. The value obtained is greater than the open ocean and straits in other studies. The high shear value confirms this in the thermocline layer. The Richardson gradient value> 0.25 is relatively constant in the thermocline layer.

An Updated Estimate of Salinity for the Atlantic Ocean Sector Using Temperature–Salinity Relationships

Simultaneous temperature and salinity profile measurements are of extreme importance for research; operational oceanography; research and applications that compute content and transport of mass, heat, and freshwater in the ocean; and for determining water mass stratification and mixing rates. Historically, temperature profiles are much more abundant than simultaneous temperature and salinity profiles. Given the importance of concurrent temperature and salinity profiles, several methods have been developed to derive salinity solely based on temperature profile observations, such as expendable bathythermograph (XBT) temperature measurements, for which concurrent salinity observations are typically not available. These empirical methods used to date contain uncertainties as a result of temporal changes in salinity and seasonality in the mixed layer, and are typically regionally based. In this study, a new methodology is proposed to infer salinity in the Atlantic Ocean from the water surface to 2000-m depth, which addresses the seasonality in the upper ocean and makes inferences about longer-term changes in salinity. Our results show that when seasonality is accounted for, the variance of the residuals is reduced in the upper 150 m of the ocean and the dynamic height errors are smaller than 4 cm in the whole study domain. The sensitivity of the meridional heat and freshwater transport to different empirical methods of salinity estimation is studied using the high-density XBT transect across 34.5°S in the South Atlantic Ocean. Results show that accurate salinity estimates are more important on the boundaries, suggesting that temperature–salinity compensation may be also important in those regions.

Unsteady Natural Convection Flow past an Infinite Cylinder with Thermal and Mass Stratification

This paper presents an analytical solution of unsteady one-dimensional free convection flow past an infinite vertical circular cylinder in a stratified fluid medium. The dimensionless coupled linear governing partial differential equations are solved by Laplace transform technique for unit Prandtl number and Schmidt number. Effects of various physical parameters are presented with graphs. Numerical values of boundary layer thickness for different parameters are presented in table. Due to the effects of thermal and mass stratifications, the velocity, temperature, and skin friction, Nusselt number shows oscillatory behaviour at smaller times and then reaches steady state at larger times.

Specific Features of Water Quality Regulation In Process of its Selective Abstraction from Reservoirs

Issues of effectiveness enhancement of the water selective intake for solution of drinking water supply problems with the Perm Chusovaya water intake as a study case have been discussed. Abstraction of water with the best consumption properties is of significant interest in the case of stable vertical water mass stratification. If water with the required properties locates in the upper layers establishment of bottom barriers around water intake head walls to cut off water intake from near-bottom layers is the most effective tool. At this the barrier parameters are to be determined by both the taken water volume and the height of the “discontinuous jump layer” position that define the water mass boundary. The barrier parameters are to be in accordance with the currently active Rules of Reservoirs Exploitation. Field and computation experiments have been carried out to elaborate the technique of stable intake of water with the required consumption properties. A series of computation experiments on impact of water intake amount on the taken water quality has been carried out in 3D with ANSYS Fluent package of computation hydrodynamics. The task was solved within the frameworks of non-stationary isothermal approach. Conclusions concerning both water quality enhancements in the conditions of significant chemical/physical properties’ heterogeneity by depth and provision of effective and stable operation of selective water intake have been obtained.

Doubly stratified effects in a free convective flow over a vertical plate with heat and mass transfer

An analysis is performed to study the effects of thermal and mass stratification in a transient free convective flow of a viscous, incompressible fluid past an isothermal vertical plate. The governing boundary layer equations are solved numerically using an implicit finite difference scheme of Crank-Nicolson type. The doubly stratified effects on the velocity, temperature and concentration are shown graphically. It is observed that an increase in thermal stratification parameter decreases the velocity, temperature profiles and increases the concentration profiles. As well, increase in mass stratification parameter decreases the velocity, concentration profiles and increases the temperature profiles. Also, the influence of the thermal and mass stratification parameter on local as well as average skin-friction, the rate of heat and mass transfer are discussed and presented graphically. The results are compared with particular solutions available in the literature. The present results are found to be in good agreement with the existing particular solution of the problem.