Numerical modelling of salinity variations due to wind and thermohaline forcing in the Persian Gulf

Salinity is an important component of the marine system. Due to shallow nature of the Persian Gulf, the salinity has been influenced by both wind driven and surface thermohaline fluxes (heat and moisture fluxes). In this study, the seasonal distribution of salinity and its variations due to wind stress and thermohaline forcing are investigated by using a three-dimensional hydrodynamic model, Coupled Hydrodynamical–Ecological Model for Regional and Shelf Seas (COHERENS). The simulation results show that the salinity in the Persian Gulf experiences dramatic spatial and temporal variations. The influence of the thermohaline forcing is considerably more than the wind stress on the salinity. The effect of the surface thermohaline fluxes over the salinity field is generally to increase the salinity for almost all the water column during the year. This effect is high during September–November where the evaporative surface salinity flux dominates over inflow of low-salinity values of Indian Ocean Surface Water. The wind forcing at the most regions of the Persian Gulf, in particular at the United Arab Emirate (UAE) coast and Bahrain–Qatar shelf, freshens the water all the year round. The wind and thermohaline forcing in March–June have strong potential to generate stratification in salinity structure. The model predictions, which are successful in simulating many features of observed pattern, indicate that the surface water of the Gulf is saltier in winter than that in spring and early summer. Both heat fluxes and wind stress play an important role for this seasonal cycle of the surface salinity.     

Preventive maintenance scheduling of multi-cogeneration plants using integer programming

Maintenance scheduling of cogeneration plants, which produce both electric power and desalinated water, is a typical complex process with long-term operations and planning problems. The plants' maintenance scheduling process has to determine the appropriate schedule for preventive maintenance, while satisfying all the system constraints and maintaining adequate system availability. It is an optimization problem and the maintenance and system constraints include the crew constraint, maintenance window constraint and time limitation constraint. In this paper, an integer linear-programming model, which has been developed, is described which schedules the preventive maintenance tasks in a multi-cogeneration plant. Results of a test example of such a plant situated in Kuwait are presented to show the applicability of the approach.     

ROYALTY INCENTIVES AND GULF OF MEXICO OIL PRODUCTION

ABSTRACT. This paper employs field‐specific estimates of Pindyck's (1978) widely cited model of natural resource supply to simulate effects of changes in federal royalty rates on the timing of exploration and output by firms in the deepwater Gulf of Mexico oil industry. Results suggest that deepwater Gulf oil production is highly inelastic with respect to changes in royalty rates. Royalty rate decreases are shown to increase early period exploration effort, result in little change in reserve additions and future production. Policy implications of this study suggest that public officials should be wary of arguments that large increases in deepwater Gulf oil field activity can be obtained from reductions in federal royalty rates‐particularly reductions in the early years of oil field development.     

Detecting the impact area of BP deepwater horizon oil discharge: an analysis by time varying coefficient logistic models and boosted trees

The Deepwater Horizon oil discharge in the Gulf of Mexico is considered to be one of the worst environmental disasters to date. The spread of the oil spill and its consequences thereof had various environmental impacts. The National Oceanic and Atmospheric Administration (NOAA) in conjunction with the Environmental Protection Agency (EPA), the US Fish and Wildlife Service, and the American Statistical Association (ASA) have made available a few datasets containing information of the oil spill. In this paper, we analyzed four of these datasets in order to explore the use of applied statistics and machine learning methods to understand the spread of the oil spill. In particular, we analysed the “gliders, floats, boats” and “birds” data. The former contains various measurements on sea water such as salinity, temperature, spacial locations, depth and time. The latter contains information on the living conditions of birds, such as living status, oil conditions, locations and time. A varying-coefficients logistic regression was fitted to the birds data. The result indicated that the oil was spreading more quickly along the East–West direction. Analysis via boosted trees and logistic regression showed similar results based on the information provided by the above data.     

A graphical exploration of the Deepwater Horizon oil spill

This paper investigates some of the immediate impacts of the Deepwater Horizon oil spill of 2010 on the environment using graphical means. The exploration focuses on the effects of the oil discharge on wildlife, the chemical pollution in the area following the spill, and salinity levels in the aftermath of the spill. Thousands of animals including birds, turtles, dolphins, and whales were found dead along the beaches and in the Gulf of Mexico in the months after the oil discharge. Levels of polycyclic aromatic hydrocarbons were found to be at dangerous levels along the coast line, making conditions for wildlife highly unfavorable. Salinity measurements, which can be used to determine currents and oil movement, are examined over time as well as geographically.     

基于灰色定权聚类法的广西北部湾海洋经济生态文明研究——灰色系统理论应用系列论文之四

广西北部湾海洋经济近年来发展迅速,与此同时,其海洋经济生态文明出现的问题也日益突出.通过借鉴生态文明指标,构建广西北部湾海洋经济生态文明指标,与珠三角相关指标数据进行对比,利用灰色定权聚类法对广西北部湾与珠三角的海洋经济生态文明程度进行评价,得出广西北部湾海洋经济生态文明为达标,珠三角海洋经济生态文明为良好的结论,从而提出调整北部湾海洋经济结构、加大海洋科技创新力度、完善海洋灾害预警与保障机制、提高海洋生态保护意识等对策建议,以期为政府制定相关决策提供科学依据.     

Dynamically equilibrium shapes and directions of motion of ocean current rings

The dynamically equilibrium shapes of a uniform-density rotating mass of liquid (a ring) in the surface layer of a quiescent stratified ocean are determined. The examination is carried out in a plane tangential to the Earth, taking into account the vertical and horizontal projections of the angular velocity of its rotation. Exact solutions of the equations of motion of an ideal incompressibe fluid are obtained, making it possible, for a linearly stratified ocean, to determine the dynamic all equilibrium shape of the interfaces of water masses and the free boundaries of cyclonic and antocyclonic rings. These shapes comprise second-order surfaces inclined to the water level in the meridian plane, the type of surfaces depending on the governing parameters of the problem. Expressions are obtained for the angles of inclination of the principal axes. For small deviations from equilibrium, due to a difference in the gravitational forces and Archimedes forces, motion of the ring occurs, governed by the inclination of the principal axes and the nature of change (increase or reduction) in the average density of the ring, determined by the ratio of the rates of diffusion of heat and salt. The displacement along the parallel comprises geostrophic motion, for the velocity of which an analytical expression is obtained. The displacement along the meridian comprises motion over an inclined plane. An analytical expression is given that relates the change in the depth of the centre of mass of the ring to the velocity of motion along the meridian through the angle of inclination of the principal axes of the ring. This explains the motion of both types of Gulf Stream ring to the south-west and of the Oyasio ring to the north-east.     

Three-dimensional numerical modeling of thermohaline and wind-driven circulations in the Persian Gulf

The Persian Gulf circulation is investigated with respect to the relevant forcing mechanism including wind stress and thermohaline surface fluxes by using a three-dimensional numerical hydrodynamic model. The model results show a correlation between the strength of the bottom layer outflow of the Persian Gulf and that of the Indian Ocean Surface Water (IOSW) inflow into the Gulf. The inflow of IOSW into the Gulf attain maximum values in May–June in conjunction with peak bottom outflow through the Hormuz Strait. The results of sensitivity experiment indicate that circulation is dominated by thermohaline flows at almost all parts of the Gulf. The heat fluxes play an essential role on the general circulation of the Persian Gulf. In spring and summer, the wind stress generates southeast-flowing surface currents of magnitude about 5 cm/s along the Saudi Arabia and Iranian coasts on the northern Gulf. In winter and autumn, due to weak static stability, the wind produces mesoscale eddies in most parts of the Gulf. In winter and spring the wind stress acts to reinforce the thermohaline circulation of deep outflow. Conversely, in summer and autumn the wind forcing acts in opposition to the thermohaline forcing and causes a bottom inflow from Oman Sea into the Gulf.     

Lagrangian coherent structures,transport and chaotic mixing in simple kinematic ocean models

Methods of dynamical system’s theory are used for numerical study of transport and mixing of passive particles (water masses, temperature, salinity, pollutants, etc.) in simple kinematic ocean models composed with the main Eulerian coherent structures in a randomly fluctuating ocean—a jet-like current and an eddy. Advection of passive tracers in a periodically-driven flow consisting of a background stream and an eddy (the model inspired by the phenomenon of topographic eddies over mountains in the ocean and atmosphere) is analyzed as an example of chaotic particle’s scattering and transport. A numerical analysis reveals a non-attracting chaotic invariant set Λ that determines scattering and trapping of particles from the incoming flow. It is shown that both the trapping time for particles in the mixing region and the number of times their trajectories wind around the vortex have hierarchical fractal structure as functions of the initial particle’s coordinates. Scattering functions are singular on a Cantor set of initial conditions, and this property should manifest itself by strong fluctuations of quantities measured in experiments. The Lagrangian structures in our numerical experiments are shown to be similar to those found in a recent laboratory dye experiment at Woods Hole. Transport and mixing of passive particles is studied in the kinematic model inspired by the interaction of a current (like the Gulf Stream or the Kuroshio) with an eddy in a noisy environment. We demonstrate a non-trivial phenomenon of noise-induced clustering of passive particles and propose a method to find such clusters in numerical experiments. These clusters are patches of advected particles which can move together in a random velocity field for comparatively long time. The clusters appear due to existence of regions of stability in the phase space which is the physical space in the advection problem.     

FORECASTING MINERAL SUPPLY FROM MINERAL RENT DATA

An optimal control model of exhaustible resources is used to clarify the long run relationship between mineral rent and depletion cost at the industry level. A standard first order condition of the time rate of change of rents is reformulated to reveal that rent data may be used to help forecast the rise in extraction costs resulting from resource depletion. This application of the theory of exhaustible resources is illustrated using historical mineral industry rent and extraction cost data. A forecast of U.S. coal extraction costs, following the method proposed in this paper, suggests that future rates of extraction cost increases will be similar to rates experienced in the past.     

A model for flow induced by steady air venting and air sparging

A numerical model for the axisymmetric subsurface flow during steady air venting and/or sparging from underground wells along the same vertical axis is presented. A common observation that for steady air injection or extraction, motion of the groundwater is negligible is first justified theoretically. Thus in the two-phase problem, only air is moving, while water remains stationary. Nevertheless there can be significant changes in water saturation because the capillary pressure varies nonlinearly with the air saturation. For pure air venting, the effects of upconing of the water table are studied. For pure air sparging, the role of air compressibility ignored by earlier authors is reassessed, and issues of design interest such as the radius of influence and discharge rates are examined. Comparisons with published measurements are discussed. Physical implications of concurrent venting and sparging are also discussed.     

Improved dust capture methods for crushing plant

The use of compressive crushing equipment such as gyratory crushers within minerals processing plants can potentially generate large quantities of dust. Remedies to this problem include the retrofitting of shrouds, enclosures, local exhaust ventilation (LEV) systems and water suppression systems. The single or combined application of these systems must be optimised to ensure they operate efficiently. It is desirable that the future design planning of such facilities include integrated dust suppression and/or removal systems to ensure material delivery rates are maintained and the welfare of the workforce is protected.     

Numerical modelling of residual flow and salinity in the Río de la Plata

The Río de la Plata discharges into the Atlantic Ocean. The particular characteristics of the study area, the variable width and shallowness of the river, the high fluvial discharges and the dynamic processes involving interactions between river discharges, tidal currents and wind, generate complex velocity and salinity fields. We applied the hydrodynamic model RMA-10 to examine the effects of various forcing (tides, flow discharge and winds) on residual currents and salinity fields in the Río de la Plata, focusing on the outer zone of the river. The RMA-10 code, developed by Ian King, is a multiparameter finite element model representing estuarine flow in three dimensions. In this study the model has been applied in a depth-averaged-baroclinic mode and a series of observed data is used for model calibration and verification. The model result shows that it is able to simulate velocity and the salinity fields with a reasonable accuracy. The analysis of residual currents in the river, when forced by freshwater discharge and astronomical tide, shows that the flow discharge takes place mainly over the shallower areas of the river and that the saline water is advected up-river through the deeper channels. The numerical simulations show that the winds from the South-West and North-East quadrants have a great influence over the salinity and velocity fields.     

Freshwater inflow requirements for the protection of the critical habitat and the drinking water sources in the Yangtze River Estuary,China

Freshwater inflow requirements (FIRs for short), which considered the requirements for protection of drinking water sources as well as the first-grade state protection wildlife (Acipenser sinensis) in larval periods, were analyzed in this paper for the Yangtze River Estuary, China. Based on the different levels of salinity objectives and the relationship between salinity and the freshwater inflows, the FIRs for the Yangtze River Estuary were determined. The estuary FIRs were determined based on the habitat ecosystem health from April to November with minimum and medium levels, from March to December with high level; and on the requirement of protection of drinking water sources in other months of the year, accordingly. Combined the salinity objectives of drinking water sources and critical habitat in the Yangtze River Estuary, the FIRs for the estuary are calculated to be 938.2 × 10⁹, 729.4 × 10⁹ and 615.5 × 10⁹ m³ in the whole year with different levels, which is equal to 100.8%, 78.4% and 66.2% of the average annual river discharge for the Yangtze River Estuary, respectively. Annual river discharges can satisfy the medium and minimum levels of FIRs for the estuary. However, the temporal variation of the actual runoff has distinct difference from the FIRs for the estuary in critical periods (May, July and August) for the habitat ecosystem, 5% of the FIRs for the estuary should be maintained from December to February for protection of drinking water sources.     

Composite mix design in the production of asbestos/cement pipes

A mathematical model is presented for the determination of optimal mix of asbestos fibres to satisfy a set of desired pipe properties which vary with pipe size, class, and material availability. The approach utilizes a linear/separable programming model which is aimed at minimizing the total cost of fibres used. The fibre properties, such as reinforcing strength, processability, and length as well as cost and stocks available are taken into account in the model. Also represented are the profile of the ideal mix relative to the required composite strength, processability, and ‘dust content’. Asbestos mixes designed using the model have been implemented in the production of asbestos/cement pipes in one of the asbestos/cement pipe manufacturing plants in the Gulf area. Optimum model mixes have demonstrated significant technical and economic merits over the conventionally designed mixes.     

Optimal investment in the reclamation of eutrophic water bodies

Eutrophication, i.e., the abnormal growth of phytoplankton, is considered in this note, which focuses on the optimal treatment of eutrophic water bodies. The issue is addressed by the use of a nonlinear model where phytoplankton and the number of wastewater treatment plants in operation are the state variables. The decision maker is a governmental agency which has to define the time pattern of investment in new plants so as to minimize the present value of environmental and treatment costs. The optimal solution is shown to have the following features. First, the optimal size for the wastewater treatment system is attained in minimum time. Subsequently, investment replaces wornout treatment plants, and phytoplankton adjusts asymptotically to its optimal equilibrium value.This work was supported by Centro Teoria dei Sistemi—CNR, Milano and by Fondazione ENI E. Mattei.     

具有两种流体的轴对称渗流的一个自由边界问题

本文处理带有两种流体的轴对称的一个自由边界问题，其中在渗流区域的上部都是油，下部是水，这是同时取油注水的一个数学模型。下面，我们将用复分析方法求出此自由边界问题的一个解，并证明其解的唯一性。     

Pelican at Risk in Salton Sea – a Delay-Induced Eco-Epidemiological Model

Elevated salinity, accelerated eutrophication, blooms of Avian botulism and dramatic water quality fluctuation are supposed to be the key factors for massive die-off of Tilapia (prey) and Pelican (predator) in the Salton sea. We modify the model of Chattopadhyay and Bairagi [Ecological Modelling 136 (2001), pp. 103-112] with an assumption that the growth rate of susceptible fish population is very high and study the dynamics of the system by introducing a delay factor in the predator response function. It is observed that the otherwise stable system exhibit a stable limit cycle solution when the lag factor attains its critical value. It is also observed that there is a high possibility of an epidemic out break in the fish as well as in the Pelican population if the predation process is delayed by a considerable amount of time. Numerical simulations for a hypothetical set of parameter values are presented to illustrate the analytical findings.     

考虑水资源税下的电厂与电网之间双重边际效应模型

以电厂和电网分开政策下引发的双重边际效应为背景,建立了考虑水资源税的序贯博弈模型。在“厂网分开”背景下,探讨了水资源税对博弈参与方(电厂、电网)最优决策、供应链效率的影响。考察了影响上网电价及供应链效率的主要因素。结论显示,水资源税的下调会负向影响电厂最优电价,进而促进电厂售电量、提升其净利润,最终削弱双重边际效应,改善了供应链效率。此外,本文运用数值算例验证了主要研究发现。     

Finite-element analysis of dispersion-affected saltwater upconing below a pumping well

A finite-element model is used to analyse the saltwater upconing mechanism which results from pumping a well, and to determine the salinity of the pumped water caused by the intrusion of saltwater. Effects of hydrodynamic dispersion and density dependencies are considered. The intrusion process and the saltwater contamination are studied by means of an axisymmetric model of upconing below a single well. The results show the significant role of dispersion and demonstrate some new effects due to density and dispersion coupling.