Transformation of Lambert Conic Conformal Coordinates from a Global Datum to a Local Datum     

E. Grafarend  F. Okeke 《Marine Geodesy》2007,30(4):297-313

This paper treats the problem of how to transform from global datum, for example, from the International Terrestrial Reference System (ITRS), to a local datum, for example, regional or national, for the practical case of the Lambert projection of the sphere or the ellipsoid-of-revolution to the cone. We design the two projection constants n(ϕ₁, ϕ₂) and m(ϕ₁) for the Universal Lambert Conic projection of the ellipsoid-of-revolution. The task to transform from a global datum with respect to the ellipsoid-of-revolution E_A,B² to local datum with respect to the alternative ellipsoid-of-revolution E_a,b², without local ellipsoidal height, is solved by an extended numerical example. Ideas in this paper could be of interest to those working with maps and coordinates transformation from global geodetic datum to local geodetic datum and vice versa, under the Universal Lambert Conic projection, and applicable to precise positioning and navigation, boundary demarcation and determination in the marine environment.  相似文献   

Short-term and interannual variability of redox-sensitive chemical parameters in hypoxic/anoxic bottom waters of the Chesapeake Bay     

Brent L. Lewis  Brian T. Glazer  Paul J. Montbriand  George W. Luther III  Donald B. Nuzzio  Timothy Deering  Shufen Ma  Stephen Theberge 《Marine Chemistry》2007,105(3-4):296-308

A combination of CTD casts, discrete bottle sampling and in situ voltammetric microelectrode profiling was used to examine changing redox conditions in the water column at a single station south of the Bay Bridge in the upper Chesapeake Bay in late July/early August, 2002–2005. Short-term (2–4 h) fluctuations in the oxic/suboxic/anoxic interface were documented using in situ voltammetric solid-state electrodes. Profiles of dissolved oxygen and sulfide revealed tidally-driven vertical fluctuations of several meters in the depth and thickness of the suboxic zone. Bottom water concentrations of sulfide, Mn²⁺ and Fe²⁺ also varied over the tidal cycle by approximately an order of magnitude. These data indicate that redox species concentrations at this site varied more due to physical processes than biogeochemical processes. Based on analysis of ADCP data, tidal currents at this station were strongly polarized, with the principal axis of tidal currents aligned with the mainstem channel. Together with the chemical data, the ADCP analysis suggests tidal flushing of anoxic bottom waters with suboxic water from north of the site. The present study is thus unique because while most previous studies have focused on processes across relatively stable redox interfaces, our data clearly demonstrate the influence of rapidly changing physical mixing processes on water column redox chemistry.Also noted during the study were interannual differences in maximum bottom water concentrations of sulfide, Mn²⁺ and Fe²⁺. In 2003, for example, heavy spring rains resulted in severe hypoxia/anoxia in June and early July. While reported storm-induced mixing in late July/early August 2003 partially alleviated the low-oxygen conditions, bottom water concentrations of sulfide, Mn²⁺ and Fe²⁺ were still much higher than in the previous year. The latter implies that the response time of the microbial community inhabiting the suboxic/anoxic bottom waters to changing redox conditions is slow compared to the time scale of episodic mixing events. Bottom water concentrations of the redox-sensitive chemical species should thus be useful as a tracer to infer prior hypoxic/anoxic conditions not apparent from ambient oxygen levels at the time of sampling.  相似文献   

A linear Boltzmann equation to model wave scattering in the marginal ice zone   总被引：1，自引：0，他引：1  

Michael H. Meylan  Diane Masson   《Ocean Modelling》2006,11(3-4):417-427

We present a linear Boltzmann equation to model wave scattering in the Marginal Ice Zone (the region of ocean which consists of broken ice floes). The equation is derived by two methods, the first based on Meylan et al. [Meylan, M.H., Squire, V.A., Fox, C., 1997. Towards realism in modeling ocean wave behavior in marginal ice zones. J. Geophys. Res. 102 (C10), 22981–22991] and second based on Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136]. This linear Boltzmann equation, we believe, is more suitable than the equation presented in Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136] because of its simpler form, because it is a differential rather than difference equation and because it does not depend on any assumptions about the ice floe geometry. However, the linear Boltzmann equation presented here is equivalent to the equation in Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136] since it is derived from their equation. Furthermore, the linear Boltzmann equation is also derived independently using the argument in Meylan et al. [Meylan, M.H., Squire, V.A., Fox, C., 1997. Towards realism in modeling ocean wave behavior in marginal ice zones. J. Geophys. Res. 102 (C10), 22981–22991]. We also present details of how the scattering kernel in the linear Boltzmann equation is found from the scattering by an individual ice floe and show how the linear Boltzmann equation can be solved straightforwardly in certain cases.  相似文献   

Multi-scale spatial variability in fish assemblages associated with Posidonia oceanica meadows in the Western Mediterranean Sea     

Joan Moranta  Miquel Palmer  Gabriel Morey  Ana Ruiz  Beatriz Morales-Nin 《Estuarine, Coastal and Shelf Science》2006,68(3-4):579

  相似文献   

Atmospherically-promoted photosynthetic activity in a well-mixed ecosystem: Significance of wet deposition events of nitrogen compounds   总被引：1，自引：0，他引：1  

C. Boulart  P. Flament  V. Gentilhomme  K. Deboudt  C. Migon  F. Lizon  M. Schapira  A. Lefebvre 《Estuarine, Coastal and Shelf Science》2006,69(3-4):449

Wet atmospheric deposition of dissolved N, P and Si species is studied in well-mixed coastal ecosystem to evaluate its potential to stimulate photosynthetic activities in nutrient-depleted conditions. Our results show that, during spring, seawater is greatly depleted in major nutrients: Dissolved Inorganic Nitrogen (DIN), Dissolved Inorganic Phosphorus (DIP) and Silicic acid (Si), in parallel with an increase of phytoplanktonic biomass. In spring (March–May) and summer (June–September), wet atmospheric deposition is the predominant source (>60%, relative to riverine contribution) for nitrates and ammonium inputs to this N-limited coastal ecosystem. During winter (October–February), riverine inputs of DIN predominate (>80%) and are annually the most important source of DIP (>90%). This situation allows us to calculate the possibility for a significant contribution to primary production in May 2003, from atmospheric deposition (total input for DIN ≈300 kg km⁻² month⁻¹). Based on usual Redfield ratios and assuming that all of the atmospheric-derived N (AD-N) in rainwater is bioavailable for phytoplankton growth, we can estimate new production due to AD-N of 950 mg C m⁻² month⁻¹, during this period of depletion in the water column. During the same episode (May 2003), photosynthetic activity rate, considered as gross primary production, was estimated to approximately 30 300 mg C m⁻² month⁻¹. Calculation indicates that new photosynthetic activity due to wet atmospheric inputs of nitrogen could be up to 3%.  相似文献   

A probability distribution for depth-limited extreme wave heights in a sea state     

Fernando J. Mndez  Sonia Castanedo 《Coastal Engineering》2007,54(12):878-882

A model for the depth-limited distribution of the highest wave in a sea state is presented. The distribution for the extreme wave height is based on a probability density function (pdf) for depth-limited wave height distribution for individual waves [Méndez, F.J., Losada, I.J., Medina, R. 2004. Transformation model of wave height distribution. Coastal Eng, Vol. 50, 97:115.] and considers the correlation between consecutive waves. The model is validated using field data showing a good representation of the extreme wave heights in the surf zone. Some important statistical wave heights are parameterized obtaining useful expressions that can be used in further calculations.  相似文献   

关于修改港工钢筋混凝土规范小偏心受压构件正截面强度计算的建议     

王清湘 《海洋工程》1995,(2)

本文提出在小偏心受压构件正截面强度计算中，取消弯曲抗压强度ｆｃｍ（Ｒｗ），采用轴心抗压强度ｆｃ，这与构件的实际破坏形态相符。对小偏心受压构件正截面强度计算提出了设计建议。特别是对工程上大量应用的矩形截面对称配筋小偏压构件提示了简捷的设计方法，与以往的近似计算方法相比具有物理概念明确，精度高，方法简捷的特点。  相似文献   

Seasonal DOC accumulation in the Black Sea: a regional explanation for a general mechanism   总被引：2，自引：0，他引：2  

Gustave Cauwet  Gaëlle Dliat  Anton Krastev  Galina Shtereva  Sylvie Becquevort  Christiane Lancelot  Andr Momzikoff  Alain Saliot  Adriana Cociasu  Lucia Popa 《Marine Chemistry》2002,79(3-4)

During three cruises in the Black Sea, organised in July 1995 and April–May 1997, biological and chemical parameters that can influence the carbon budget were measured in the water column on the NW shelf, particularly in the mixing zone with Danube River waters. We observed in early spring (end of April–May) conditions an important input of freshwater organisms that enhanced the microbial activity in the low salinity range. High bacterial activity regenerates nitrogen in the form of nitrates, but is also responsible for an important consumption of ammonium and phosphate, leading to a high N/P ratio and a strong deficit in phosphorus. The consequence is a limitation of phytoplankton development but also a production of carbohydrates that accumulate all along the salinity gradient. These mechanisms are responsible for a seasonal accumulation of dissolved organic carbon (DOC) that increases from 210 μM in winter to about 280 μM in summer. All this excess DOC disappears during winter, probably degraded by bacterial activity. The degradation of carbon-rich organic matter increases the phosphorus demand by bacteria bringing limitation to phytoplankton primary production.  相似文献   

Effect of free surface and strut on fins attached to a strut     

C. M. Lee  I. R. Park  H. H. Chun  S. J. Lee 《Ocean Engineering》2001,28(1)

An extensive experimental and computational investigation of the combined and separate effects of free surface and body on the lift characteristics of a pair of fins attached to a strut and fin alone is conducted. The results reveal that the free-surface effect becomes significant when the depth of submergence to chord ratio (H/c) is less than three. The effect of the strut is also realized for shallower depth of submergence of the fins through free-surface deformation leading to a significant change in the incidence angle of the flow to the fins. The numerical results based on the Higher Order Boundary Element Method with the linearized free-surface condition show good agreement with the experimental results for fin (foil) alone even at shallow submergence, but some discrepancies appear for the fin attached to the strut at higher speeds mostly due to the neglect of the nonlinear free-surface effect.  相似文献   

鲁苏榴辉岩的地球化学     

韩宗珠 《中国海洋大学学报(自然科学版)》1994,(1)

以微量元素、稀土元素、Ｓｒ和Ｎｄ同位素变异特征为依据，确定鲁苏榴辉岩为多成因、多来源和多阶段，指出主要是在印支期扬子陆块与华北陆块碰撞造山作用过程中，挤入的上地幔碎片以及不同原岩类型的壳内高压变质岩碎块。燕山晚期的区域构造热事件使得某些榴辉岩的同位素体系再平衡。  相似文献