全球Stokes 漂流的时空分布特征研究

利用海浪模式WWIII(Wave Watch III)2008年的模拟结果对海面Stokes漂流、Stokes输运、Stokes深度以及全球Langmuir数的年平均分布特征和季节平均分布特征分别进行了详细的研究与分析。结果表明,海面Stokes漂流和Stokes输运均呈现高纬度偏大的特征,以南极绕极流海域最为突出。全球大部分海域Stokes漂流影响深度在20 m以内,呈现大洋东部偏大,西部偏小的分布特征。全球大部分海域的混合作用是剪切不稳定性和Langmuir湍效应并存的状态,甚至有些海域是以Langmuir湍效应为主。因此,在进行大尺度的海洋数值模拟时,应该考虑波浪导致的混合效应。     

中国物理海洋学研究70年:发展历程、学术成就概览

本文概略评述新中国成立70年来物理海洋学各分支研究领域的发展历程和若干学术成就。中国物理海洋学研究起步于海浪、潮汐、近海环流与水团，以及以风暴潮为主的海洋气象灾害的研究。随着国力的增强，研究领域不断拓展，涌现了大量具有广泛影响力的研究成果，其中包括:提出了被国际广泛采用的“普遍风浪谱”和“涌浪谱”，发展了第三代海浪数值模式；提出了“准调和分析方法”和“潮汐潮流永久预报”等潮汐潮流的分析和预报方法；发现并命名了“棉兰老潜流”，揭示了东海黑潮的多核结构及其多尺度变异机理等，系统描述了太平洋西边界流系；提出了印度尼西亚贯穿流的南海分支(或称南海贯穿流)；不断完善了中国近海陆架环流系统，在南海环流、黑潮及其分支、台湾暖流、闽浙沿岸流、黄海冷水团环流、黄海暖流、渤海环流，以及陆架波方面均取得了深刻的认识；从大气桥和海洋桥两个方面对太平洋–印度洋–大西洋洋际相互作用进行了系统的总结；发展了浅海水团的研究方法，基本摸清了中国近海水团的分布和消长特征与机制，在大洋和极地水团分布及运动研究方面也做出了重要贡献；阐明了南海中尺度涡的宏观特征和生成机制，揭示了中尺度涡的三维结构，定量评估了其全球物质与能量输运能力；基本摸清了中国近海海洋锋的空间分布和季节变化特征，提出了地形、正压不稳定和斜压不稳定等锋面动力学机制；构建了“南海内波潜标观测网”，实现了对内波生成–演变–消亡全过程机理的系统认识；发展了湍流的剪切不稳定理论，提出了海流“边缘不稳定”的概念，开发了海洋湍流模式，提出了湍流混合参数化的新方法等；在海洋内部混合机制和能量来源方面取得了新的认识，并阐述了混合对海洋深层环流、营养物质输运等过程的影响；研发了全球浪–潮–流耦合模式，推出一系列海洋与气候模式；发展了可同化主要海洋观测数据的海洋数据同化系统和用于ENSO预报的耦合同化系统；建立了达到国际水准的非地转(水槽/水池)和地转(旋转平台)物理模 型实验平台；发展了ENSO预报的误差分析方法，建立了海洋和气候系统年代际变化的理论体系，揭示了中深层海洋对全球气候变化的响应；初步建成了中国近海海洋观测网；持续开展南北极调查研究；建立了台风、风暴潮、巨浪和海啸的业务化预报系统，为中国气象减灾提供保障；突破了国外的海洋技术封锁，研发了万米水深的深水水听器和海洋光学特性系列测量仪器；建立了溢油、危险化学品漂移扩散等预测模型，为伴随海洋资源开发所带来的风险事故的应急处理和预警预报提供科学支撑。文中引用的大量学术成果文献(每位第一作者优选不超过3篇)显示，经过70年的发展，中国物理海洋学研究培养了一支实力雄厚的科研队伍，这是最宝贵的成果。这支队伍必将成为中国物理海洋学研究攀登新高峰的主力军。     

The effect of the wave-induced mixing on the upper ocean temperature in a climate model

The significant underestimation of sea surface temperature （SST） and the temperature in the upper ocean is one of common problems in present climate models. The influence of the wave-induced mixing on SST and the temperature in the upper ocean was examined based on a global climate model. The results from the model coupled with wave-induced mixing showed a significant improvement in the simulation of SST and the temperature in the upper ocean compared with those of the original model without wave effects. Although there has still a cold bias, the new simulation is much closer to the climatology, especially in the northern ocean and tropical ocean. This study indicates that some important physical processes in the accurate simulation of the ocean may be ignored in present climate models, and the wave-induced mixing is one of those factors. Thus, the wave-induced mixing （ or the effect of surface waves） should be incorporated properly into climate models in order to simulate or forecast the ocean, then climate system, more accurately.     

A general ecosystem model for applications to primary productivity and carbon cycle studies in the global oceans

We have developed a general 1-D multi-component ecosystem model that incorporates a skillful upper ocean mixed layer model based on second moment closure of turbulence. The model is intended for eventual incorporation into coupled 3-D physical–biogeochemical ocean models with potential applications to modeling and studying primary productivity and carbon cycling in the global oceans as well as to promote the use of chlorophyll concentrations, in concert with satellite-sensed ocean color, as a diagnostic tool to delineate circulation features in numerical circulation models. The model is nitrogen-based and the design is deliberately general enough and modular to enable many of the existing ecosystem model formulations to be simulated and hence model-to-model comparisons rendered feasible. In its more general form (GEM10), the model solves for nitrate, ammonium, dissolved nitrogen, bacteria and two size categories of phytoplankton, zooplankton and detritus, in addition to solving for dissolved inorganic carbon and total alkalinity to enable estimation of the carbon dioxide flux at the air–sea interface. Dissolved oxygen is another prognostic variable enabling air–sea exchange of oxygen to be calculated. For potential applications to HNLC regions where productivity is constrained by the availability of a trace constituent such as iron, the model carries the trace constituent as an additional prognostic variable. Here we present 1-D model simulations for the Black Sea, Station PAPA and the BATS site. The Black Sea simulations assimilate seasonal monthly SST, SSS and surface chlorophyll, and the seasonal modulations compare favorably with earlier work. Station PAPA simulations for 1975–1977 with GEM5 assimilating observed SST and a plausible seasonal modulation of surface chlorophyll concentration also compare favorably with earlier work and with the limited observations on nitrate and pCO₂ available. Finally, GEM5 simulations at BATS for 1985–1997 are consistent with the available time series. The simulations suggest that while it is generally desirable to employ a comprehensive ecosystem model with a large number of components when accurate depiction of the entire ecosystem is desirable, as is the prevailing practice, a simpler formulation such as GEM5 (N²PZD model) combined with assimilation of remotely sensed SST and chlorophyll concentrations may suffice for incorporation into 3-D prediction models of primary productivity, upper ocean optical clarity and carbon cycling.     

Parameterization of vertical mixing in the Weddell Sea

A series of vertical mixing schemes implemented in a circumpolar coupled ice–ocean model of the BRIOS family is validated against observations of hydrography and sea ice coverage in the Weddell Sea. Assessed parameterizations include the Richardson number-dependent Pacanowski–Philander scheme, the Mellor–Yamada turbulent closure scheme, the K-profile parameterization, a bulk mixed layer model and the ocean penetrative plume scheme (OPPS). Combinations of the Pacanowski–Philander parameterization or the OPPS with a simple diagnostic model depending on the Monin–Obukhov length yield particularly good results. In contrast, experiments using a constant diffusivity and the traditional convective adjustment cannot reproduce the observations. An underestimation of wind-driven mixing in summer leads to an accumulation of salt in the winter water layer, inducing deep convection in the central Weddell Sea and a homogenization of the water column. Large upward heat fluxes in these simulations lead to the formation of unrealistic, large polynyas in the central Weddell Sea after only a few years of integration. Furthermore, spurious open-ocean convection affects the basin-scale circulation and leads to a significant overestimation of meridional overturning rates. We conclude that an adequate parameterization of both wind-induced mixing and buoyancy-driven convection is crucial for realistic simulations of processes in seasonally ice-covered seas.     

Abyssal recipes II: energetics of tidal and wind mixing

Without deep mixing, the ocean would turn, within a few thousand years, into a stagnant pool of cold salty water with equilibrium maintained locally by near-surface mixing and with very weak convectively driven surface-intensified circulation. (This result follows from Sandström’s theorem for a fluid heated and cooled at the surface.) In this context we revisit the 1966 “Abyssal Recipes”, which called for a diapycnal diffusivity of 10^-4m²/s (1 cgs) to maintain the abyssal stratification against global upwelling associated with 25 Sverdrups of deep water formation. Subsequent microstructure measurements gave a pelagic diffusivity (away from topography) of 10^-5 m²/s — a low value confirmed by dye release experiments.A new solution (without restriction to constant coefficients) leads to approximately the same values of global upwelling and diffusivity, but we reinterpret the computed diffusivity as a surrogate for a small number of concentrated sources of buoyancy flux (regions of intense mixing) from which the water masses (but not the turbulence) are exported into the ocean interior. Using the Levitus climatology we find that 2.1 TW (terawatts) are required to maintain the global abyssal density distribution against 30 Sverdrups of deep water formation.The winds and tides are the only possible source of mechanical energy to drive the interior mixing. Tidal dissipation is known from astronomy to equal 3.7 TW (2.50±0.05 TW from M₂ alone), but nearly all of this has traditionally been allocated to dissipation in the turbulent bottom boundary layers of marginal seas. However, two recent TOPEX/POSEIDON altimetric estimates combined with dynamical models suggest that 0.6–0.9 TW may be available for abyssal mixing. A recent estimate of wind-driving suggests 1 TW of additional mixing power. All values are very uncertain.A surprising conclusion is that the equator-to-pole heat flux of 2000 TW associated with the meridional overturning circulation would not exist without the comparatively minute mechanical mixing sources. Coupled with the findings that mixing occurs at a few dominant sites, there is a host of questions concerning the maintenance of the present climate state, but also that of paleoclimates and their relation to detailed continental configurations, the history of the Earth–Moon system, and a possible great sensitivity to details of the wind system.     

在大洋环流模型中对应于惯性内波破碎的垂直混合的一个参数化方案

Based on the theoretical spectral model of inertial internal wave breaking(fine structure) proposed previously, in which the effects of the horizontal Coriolis frequency component f-tilde on a potential isopycnal are taken into account, a parameterization scheme of vertical mixing in the stably stratified interior below the surface mixed layer in the ocean general circulation model(OGCM) is put forward preliminarily in this paper. Besides turbulence, the impact of sub-mesoscale oceanic processes(including inertial internal wave breaking product) on oceanic interior mixing is emphasized. We suggest that adding the inertial internal wave breaking mixing scheme(F-scheme for short) put forward in this paper to the turbulence mixing scheme of Canuto et al.( T-scheme for short) in the OGCM, except the region from 15°S to 15°N. The numerical results of F-scheme by using WOA09 data and an OGCM(LICOM, LASG/IAP climate system ocean model) over the global ocean are given. A notable improvement in the simulation of salinity and temperature over the global ocean is attained by using T-scheme adding F-scheme, especially in the mid- and high-latitude regions in the simulation of the intermediate water and deep water. We conjecture that the inertial internal wave breaking mixing and inertial forcing of wind might be one of important mechanisms maintaining the ventilation process. The modeling strength of the Atlantic meridional overturning circulation(AMOC) by using T-scheme adding F-scheme may be more reasonable than that by using T-scheme alone, though the physical processes need to be further studied, and the overflow parameterization needs to be incorporated. A shortcoming in F-scheme is that in this paper the error of simulated salinity and temperature by using T-scheme adding F-scheme is larger than that by using T-scheme alone in the subsurface layer.     

印度尼西亚海潮致混合研究现状与展望

印度尼西亚海(简称印尼海)位于热带太平洋和印度洋交汇的海域,是全球最大的内潮生成海域。内潮耗散导致强烈的潮致混合,一方面将温跃层以下的海水卷入上层,降低印尼海海表温度,之后通过海气相互作用产生显著的天气和气候效应;另一方面对穿越印尼海的印度尼西亚贯穿流的物质与能量输运也有着重要影响。自Arlindo计划以来,人们对印尼海潮致混合的认识不断深化,并通过在海洋环流数值模式中考虑印尼海强潮致混合过程,提升了对印尼海和全球大洋环流的模拟效果。但由于缺乏现场观测资料和针对性的潮致混合参数化方案,印尼海潮致混合特征的定量描述及其在海洋环流与气候模式中的表达尚未完全解决。本研究对印尼海潮致混合及其在海洋环流和气候数值模式中的应用的最新研究成果进行了概述和展望,并对未来该海域混合观测方案和潮致混合参数化方案提出了针对性建议。     

A Study of the Performances of Different Turbulence Schemes in Numerical Simulation of Hydrodynamics of a Semi-Closed Sea (Persian Gulf)

Complex process of turbulent mixing in Persian Gulf that is a semi-closed sea makes it a good media to test the performance of different turbulence schemes. In this research, we used the 3D ocean model COHERENS (COupled Hydrodynamical Ecological model for REgioNal Shelf seas) for the Persian Gulf with the open boundary in the Hormuz Strait. Of the turbulence schemes for the vertical diffusion available in the COHERENS, we tested four models to investigate the hydrodynamic characteristics of the Persian Gulf. The results show that all of the schemes presented the sea surface salinity (SSS) distribution rather accurately but the k-l and flow-dependent models results have better agreements with observations. The most noticeable difference between the results of four schemes is the differences found in the simulation of turbulent parameters. The turbulent closure schemes generally provide better results, but the algebraic schemes show turbulent parameters far from reality and they do not show substantial changes with time. Generally, the vertical structures of turbulence in the water basins and parameterization of turbulence in water column is very sensitive to the selection of the type of the turbulence scheme. However, large-scale structures that take place within the inflow and outflow area are approximately quasi-horizontal, and the vertical small-scale turbulence does not affect them as much. As a result, they show less sensitivity to the performance of various turbulence schemes.     

历次核试验进入海洋的~(137)Cs对中国近海影响的模拟研究

1945年以来,世界各主要核国家进行了数千次核试验,这些核试验产生的绝大部分放射性物质通过多种途径进入海洋,对海洋环境造成放射性污染。本文建立了一个准全球海洋的放射性物质输运和扩散数值模式,通过数值模拟手段评估了历史核试验释放的放射性物质137 Cs对中国近海海洋环境的影响。本文借助前人工作评估了核试验释放137Cs进入海洋的途径和总量;通过比较模拟结果与观测资料,表明本文建立的放射性物质模式能够较好地模拟出137Cs在中国近海及其邻近海域的分布情况和随时间演变特征;模拟结果表明中国近海里的137Cs浓度在20世纪50年代中期达到最大,其中吕宋海峡海域137Cs浓度最高,达80.99Bq/m3;进一步分析了2011年3月份日本福岛核事故前中国近海137Cs浓度分布状况,2011年整个中国近海137Cs浓度介于1.0~1.6Bq/m3间,且其浓度垂向分布较均匀,相对封闭的南海浓度略高于其他海域。     

The global importance and context of methane escape from the seabed

Seabed fluid flow includes volcanic and hydrothermal fluid emissions from ocean spreading centres, island arcs, and intra-plate volcanism, and groundwater flows in some coastal areas. Of direct concern to this paper is the escape of methane from the seabed. Escaping methane may be of microbial, thermogenic or abiogenic origin. Escapes occur in all seas and oceans, in coastal waters, on continental shelves, slopes and rises, the deep oceans, and deep ocean trenches. These represent a variety of geological contexts on passive continental margins, at convergent plate margins (accretionary wedges) and transform plate boundaries. Seepage is clearly widespread, and it contributes methane to the biosphere, the hydrosphere and the atmosphere, thus making up an important part of the global carbon cycle.     

海洋湍流模式应用研究

海洋湍流模型研究自二十世纪 70年代中发展至今 ,在海洋动力学研究中 ,特别是关于混合 /层化研究中广泛应用 ,近年来由于认识到湍流对海洋生物过程的重要影响 ,对海洋湍流的客观描述更加关注。文中详细介绍了几个主要海洋动力学模型中的湍流封闭模式 ,如 HAMSOM中的Prandtl混合长模型、Johns模式中的 k-方程模型、POM中的 k- kl模型、水动力学中常用的 k-ε模型等等 ,介绍了海洋湍流模型的应用。对于湍流模型的使用提出针对具体问题选择的原则 ,复杂的并非最优的。     

湍流混合输运通量的数学物理描述基础——高确定性闭合的湍流二阶矩和基本特征量控制方程组

湍流,在海洋动力系统其他类运动的控制方程组中,主要以输运通量剩余项的形式出现,它是最重要的海洋混合运动主体。本文的主要研究目标是,在湍流最新研究成果及其子系统控制方程组基础上,提出高确定性的二阶矩闭合原理,导出闭合的二阶矩和基本特征量控制方程组,建立湍流输运通量的数学物理描述基础。现有的湍流基本特征量方程组,其右端项的闭合办法实际上是非独立的。因此要么在今后的研究中引入独立的闭合办法,要么回归到湍流的现场实验分析研究,给出独立的特征量实验关系,从而有可能得到湍流混合系数的解析估计。     

区域性海洋环流数值模式研究及对南海环流与海峡流量的模拟

基于MOM模式的物理框架,妥善考虑了开边界的物理过程,改造和发展了一个区域海洋数值模式。本模式不仅可以方便地调整开边界条件,使之满足边界的特定物理条件,而且可以方便地做针对性修改,使模式更加可靠。改进后的模式具有MOM模式物理概念明确、公式便于理解、结果便于表达的全部特点,同时克服了MOM模式边界条件不完整、程序不易调整、参数难以改变的缺点。区域性模式比全球模式的计算速度快很多倍,可以成为区域性研究的有效工具。将此模式应用于南海,利用Hellerman＆Rosenstein气候态风应力驱动模式10a,得到与全球模式效果相当的结果。模式模拟结果展现了南海流场的季节特征,在模式分辨率下表现出了多涡结构。根据模拟的流场计算了南海与其它海域的水交换通量。在年平均意义下,外海水通过吕宋海峡进入南海,南海水通过台湾海峡、民都洛海峡和卡里马塔海峡流出南海。各海峡水通量具有明显的季节变化。     

Towards a mesoscale eddy closure

A turbulence closure for the effect of mesoscale eddies in non-eddy-resolving ocean models is proposed. The closure consists of a prognostic equation for the eddy kinetic energy (EKE) that is integrated as an additional model equation, and a diagnostic relation for an eddy length scale (L), which is given by the minimum of Rhines scale and Rossby radius. Combining EKE and L using a standard mixing length assumption gives a diffusivity (K), corresponding to the thickness diffusivity in the [Gent, P.R., McWilliams, J.C. 1990. Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr. 20, 150–155] parameterisation. Assuming downgradient mixing of potential vorticity with identical diffusivity shows how K is related to horizontal and vertical mixing processes in the horizontal momentum equation, and also enables us to parameterise the source of EKE related to eddy momentum fluxes.The mesoscale eddy closure is evaluated using synthetic data from two different eddy-resolving models covering the North Atlantic Ocean and the Southern Ocean, respectively. The diagnosis shows that the mixing length assumption together with the definition of eddy length scales is valid within certain limitations. Furthermore, implementation of the closure in non-eddy-resolving models of the North Atlantic and the Southern Ocean shows consistently that the closure has skill at reproducing the results of the eddy-resolving model versions in terms of EKE and K.     

Errors in recent ocean tide models: possible origin and cause

Recently, the TOPEX/POSEIDON Science Working Team has recommended the FES95.2.1 and CSR3.0 ocean tide models for reprocessing the TOPEX/POSEIDON Geophysical Data Records. Without doubt, the performance of these models, especially in the deep oceans, is excellent. However, from a comparison of these hydrodynamically consistent models with the purely empirical DW3.2 and DEOS96.1 models, it appears that FES95.2.1 and CSR3.0 are affected by basin boundary related errors which are caused by the basin-wise solution procedure of the FES ocean tide model series. In their turn, the empirical DW3.2 and DEOS96.1 models seem to suffer from significant errors in the Antarctic seas due to the seasonal growth and decay of Antarctic sea ice. Also, bathymetry-induced differences were found between the hydrodynamically consistent models and the empirical models. Concerning these differences, TOPEX/POSEIDON and ERS-1 crossover statistics unfortunately do not provide conclusive results on which models are in error.     

Wind-induced shear dispersion and genesis of the shelf-break front

Through a simple analytical model, we examine the shear dispersion associated with oscillatory winds in an unstratified coastal ocean. As noted previously in the tidal regime, the vertical-integrated (total) horizontal diffusivity has a maximum where the water depth equals the diffusive depth – defined as the reach of the vertical diffusion during one forcing cycle. Due principally to the long synoptic timescale that characterizes the wind forcing, this depth lies over the outer shelf. When combined with effective mixing of the slope water by meso-scale eddies, the total diffusivity exhibits a minimum around the shelf break, thus facilitating frontogenesis. Due again to the long forcing period, the bottom Ekman flow is well developed at the diffusive depth, which would accentuate the gradient enhancement of the front over the inshore water, which however is bounded above by doubling.Calculations from a primitive-equation numerical model are carried out for both unstratified and stratified oceans. From an initially uniform property gradient, a front is seen to emerge around the shelf break after an oscillating wind is switched on, in a visual demonstration of the proposed frontogenesis. The unstratified solution closely agrees with the analytical solution, and although the front is not particularly sharp, it is comparable to that observed. The stratified solution renders a more realistic simulation of the observed front, but it retains the basic features, suggesting the dominance of the proposed mechanism even in the presence of the cross-frontal circulation.     

Determination of water component age in ocean models: application to the fate of North Atlantic Deep Water

A method allowing the calculation of both concentration and age of an individual water component is used to examine the penetration and fate of North Atlantic Deep Water (NADW) in a global ocean model. The method is consistent with the recent theory of water component age by Delhez et al. Its application in ocean models is straightforward and involves specification of two ideal tracers, and its efficacy is verified here via comparison with water component ages obtained by a second method, involving the time history of a single ideal tracer, and whose application is rather more restricted. Age estimates by the two methods are compared in the case of an interior ocean source region (suitable for marking the model's NADW, and forming the main focus of the study) and in the case of a ocean surface source region (featuring high density surface water in the far Northern Atlantic). The concentration and age of NADW are determined for two versions of the model, differing only in the inclusion or exclusion of isoneutral diffusion. The age and, especially, the concentration of NADW in the deep Southern, Indian and Pacific Oceans are significantly lower in the version with isoneutral diffusion. Both versions indicate that most of the NADW ultimately reaches the surface in the model Southern Ocean.