1993—2011年北大西洋与北太平洋的波浪变化及其原因探究

基于1993—2011年的7套卫星高度计数据,分析北大西洋和北太平洋的波浪变化趋势;利用NCEP/NCAR提供的月平均风场及SLP(Surface Level Pressure)数据,分析风场和SLP的空间变化特征,并通过主成分分析进一步考察了波浪变化与SLP的相关关系。结果表明:北大西洋波浪变化趋势的空间分布呈偶极子形态,西南区域为增大趋势,东北区域为减小趋势;而北太平洋波浪变化的主要特征是在中纬度带呈明显的减小趋势;比较而言,波浪变化趋势的空间形态与SLP变化的空间分布特征更接近,波浪主要模态的空间分布及时间系数与SLP距平场的震荡特征十分吻合,大尺度背景场SLP的变化对波浪的长期变化趋势有重要的影响。     

均匀介质n维随机波动的空间结构

研究了均匀介质中n维随机波动的空间结构.导出了外观振幅、波数和相位的联合分布,据此分布,所有与空间有关的波要素的统计分布皆可导出.定义了外观波数谱并得到了其平衡区指数的上界为一(n+2).二维时,海浪外观波数谱平衡区指数的上界与Phillips通过动力学分析导出的Fourier波数谱平衡区指数完全一样.     

海浪外观谱及其平衡域

定义了海浪能量的广义或n阶外观分布,导出了n阶海浪外观谱的解析形式,讨论了n阶外观谱的平衡域.结果表明,n阶外观谱的平衡域指数为-(3+n);平衡域指数上界为-3.任何波动现象,只要Fourier迭加原理和射线理论对它们的描述足够准确,则本文的结论皆成立.     

GENERAL THEORY FOR APPARENT ENERGY DISTRIBUTION OF SEA WAVES

lwrRODUcrIONSeawavesarerecognindasacrucialfaCtorinengineeringandoffshorestruCturede-signsandconstitutCanimPoftantpartintheoreticalstudiesandapplicati0ns.TocopewiththecomPlexityofseawaves,alinearrandomwaveshomogeneousandstationarythe-oryisintrodutalwhereintwomodeIsdescribetheoonnsurfaeedisplacement.Inthefirstone,thesurfaeedisplaerentchangingwithlocationandtheisexpnssedingeneralitalFouriertransform,wherethefrequencyspeCtrumE(co)andwavenumberspodrumEoocanbedefined.Theotherwavemodelisbasedo…     

南太平洋Stokes漂流在厄尔尼诺衰退过程中的降温作用

赤道东太平洋海表面温度的变化在全球气候变化中扮演着重要的角色,波浪是影响海表面温度的重要因素。为了进 一 步 研 究 波 浪 对 全 球 气 候 的 影 响,利 用 ECMWF(European Centrefor Medium-Range WeatherForecasts)发布的波浪参数、海表面温度(SeaSurfaceTemperature,SST)等再分析数据,采用 EOF(EmpiricalOrthogonalFunction)分析和超前滞后相关分析等方法,分析了南太平洋涌浪区Stokes漂流与厄尔尼诺事件的关系。首先选用一种涌浪指标和多个涌浪特征值总结了全球的涌浪特征,得到涌浪在低纬、南半球和大洋东边界更占优的结论,并由此划定南太平洋涌浪区,发现了其连接南大洋和赤道东太平洋的通道作用。进而研究了南太平洋涌浪区Stokes漂流对赤道东太平洋SST的影响,结果显示:在厄尔尼诺事件发生后,该区域的经向 Stokes漂流会产 生强化,波浪诱导的Stokes漂流会将高纬冷水输送到低纬海域,使得低纬海域降温,加速厄尔尼诺事件的衰退,进而影响到全球气候。本文为解释厄尔尼诺的衰退提供了新的思路,也为波浪的大尺度效应研究开辟了新的方向。     

Wave characteristics and extreme parameters in the Bohai Sea

This paper is aimed at the whole Bohai Sea,as the complement and improvement of wave characteristics and extreme parameters.Wave fields were simulated in the Bohai Sea by using wave model SWAN from 1985 to 2004.The input data based on the hindcast of high-resolution wind fields from RAMS and water level fields from POM,which have been tested and verified well.Comparisons of significant wave heights between simulation and station observations show a good agreement in general.By statistical analysis,the wave characteristics such as significant wave heights, dominant wave directions and their seasonal variations are discussed.In addition,main wave extreme parameters and directional extreme values particularly for 100-year return period are investigated.     

Modelling the upwelling offthe east Hainan Island coast in summer 2010

A synoptic-scale upwelling event that developed off the east coast of the Hainan Island(EHIU) in the summer of 2010 is defi ned well via processing the Moderate Resolution Imaging Spectroradiometer(MODIS) sea surface temperature(SST) data. The Regional Ocean Modeling System(ROMS) with high spatial resolution has been used to investigate this upwelling event. By comparing the ROMS results against tide station data, Argo fl oat profi les and MODIS SST, it is confi rmed that the ROMS reproduces the EHIU well. The cooler-water core(CWC) distinguished by waters(27) 27.5°C in the EHIU, which occurred in the east Qiongzhou Strait mouth area and was bounded by a high temperature gradient, was the focus of this paper. Vertical structure of the CWC suggests that interaction between the westward fl ow and the bathymetry slope played a signifi cant role in the formation of CWC. Numerical experiments indicated that the westward fl ow in the Qiongzhou Strait was the result of tidal rectifi cation over variable topography(Shi et al., 2002), thus tides played a critical role on the development of the CWC. The negative wind stress curl that dominated the east Qiongzhou Strait mouth area suppressed the intensity of the CWC by 0.2–0.4°C. Further, nonlinear interaction between tidal currents and wind stress enhanced vertical mixing greatly, which would benefi t the development of the CWC.     

基于近20年的SWAN模式海浪模拟结果的南海波浪能分布、变化研究

由于南海海域地形复杂,岛屿众多,不可避免的会产生折射、变浅、绕射、波浪破碎、非线性波相互作用等近岸物理过程。因此采用以风场驱动的第三代海浪数值模式SWAN,可得到南海海域1986年1月至2005年12月较高分辨率的波浪场,计算了南海海域的波浪能流密度,综合考虑能流密度的大小和14个站位能流密度分级统计的特征等方面对南海海域波浪能资源进行了研究,寻找该海域波浪能资源的相对优势区域,为建立海上波浪能电站提供科学依据。     

Evaluation of the simulation capability of the Wavewatch Ⅲ model for Pacific Ocean wave

Wave climate analysis and other applications for the Pacific Ocean require a reliable wave hindcast. Five source and sink term packages in the Wavewatch III model(v3.14 and v4.18) are compared and assessed in this study through comprehensive observations, including altimeter significant wave height, advanced synthetic aperture radar swell, and buoy wave parameters and spectrum. In addition to the evaluation of typically used integral parameters, the spectra partitioning method contributes to the detailed wave system and wave maturity validation. The modified performance evaluation method(PS) effectively reduces attribute numbers and facilitates the overall assessment. To avoid possible misleading results in the root mean square error-based validations, another indicator called HH(indicating the two authors) is also calculated to guarantee the consistency of the results. The widely used Tolman and Chalikov(TC) package is still generally efficient in determining the integral properties of wave spectra but is physically deficient in explaining the dissipation processes. The ST4 package performs well in overall wave parameters and significantly improves the accuracy of wave systems in the open ocean. Meanwhile, the newly published ST6 package is slightly better in determining swell energy variations. The two packages(ACC350 and BJA) obtained from Wavewatch III v3.14 exhibit large scatters at different sea states. The three most ideal packages are further examined in terms of reproducing waveinduced momentum flux from the perspective of transport. Stokes transport analysis indicates that ST4 is the closest to the NDBC-buoy-spectrum-based transport values, and TC and ST6 tend to overestimate and underestimate the transport magnitude, respectively, in swell mixed areas. This difference must be considered,particularly in air–wave–current coupling research and upper ocean analysis. The assessment results provide guidance for the selection of ST4 for use in a background Pacific Ocean hindcast for high wave climate research and China Sea swell type analysis.     

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。