【作者】 邓增安；

【导师】 赵栋梁； 吴克俭； 谢立安；

【作者基本信息】 中国海洋大学 ， 物理海洋学， 2009， 博士

【摘要】 本论文由两部分组成：第一部分主要关注于海表面海水运动的速度对上层海洋现象的影响,其中包括风应力、海表面流场、海表面温度、海-气热通量、以及海表面边界层厚度；第二部分具体研究了波浪引起的大尺度Coriolis-Stokes力效应对上层海流的影响。为了完成本论文的研究目标,建立了两个耦合模式：HYCOM-WINDS风-流耦合模式,和SWAN-POM浪-流耦合模式。通过在基于波陡和风速的拖曳系数经验参数化方案中考虑海表面海水运动速度的影响,研究计算了1958-2001年间全球风应力拖曳系数和风应力的分布情况。计算中使用的全球海表面流场来自海洋模式HYCOM,波浪参数输出自波浪模式WW3。通过分析拖曳系数和风应力的空间变化情况得出结论；海表面海水运动速度对风应力平均能够产生5%左右的影响；同时,考虑海表面海水运动速度的影响后,海洋模拟结果将得到一定程度的提高。另外,本文还利用地球耦合系统框架(ESMF)、海洋模式HYCOM以及Donelan etal.(1997)提出的风应力计算关系式的改良版建立了一个风.流耦合系统。此耦合系统被应用于全球风应力和海表面流相互作用研究。在此研究中,海表面流的速度被同时考虑到风应力的计算以及海-气热通量的计算之中；包含了海表面海水运动速度影响的风应力将被用作HYCOM的驱动。结果表明：海表面海水运动速度对海表面流场、海-气热通量、和海表面边界层厚度都会产生明显影响。将模拟的海表面温度和TOGA TAO浮标资料进行对比发现,耦合模式的模拟结果要优于非耦合模式的结果,这也证实了海表面海水运动速度在海洋模拟中是一个不容忽视的物理过程。通过计算2000年涌浪指标(swell index)的全球分布,发现太平洋东边界赤道附近区域存在涌浪池。利用ECMWF再分析波浪资料,计算出2000年全球月平均波浪体积输运。比较2000年全球月平均波浪体积输运和2000年QUICKSCAT月平均风场,发现在赤道太平洋东边界涌浪池区域内的波浪输运方向和风向存在很大的差别,两者方向相差大约90°。这进一步验证了这个地区涌浪池存在的真实性。研究发现,赤道太平洋东边界涌浪主要来源于北太平洋和南太平洋的西风带对应的海区。在涌浪池区域内分别在2.5°S和2.5°N取两条边界(边界起点为125°W，终点为美洲大陆西边界),计算通过这两条边界进入赤道区域涌浪的Stokes体积净输运量。结果表明,不同月份通过南、北两条边界波浪的净输运量与当月南、北太平洋西风带的风浪强度密切相关。接下来,利用HYCOM在三个不同区域进行的六个控制性实验研究了波浪诱导的Coriolis-Stokes力对包括海洋环流、温度以及混合过程在内的海洋现象的影响。Coriolis-Stokes力是利用波浪模式WW3的模拟结果来进行计算的,并像风应力一样用做HYCOM的上边界驱动。模拟结果表明：1)在三个水平分辨率不同的区域上,HYCOM都可以成功地模拟海洋上层环流,南中国海、墨西哥湾,以及湾流区域的上层环流特征都被成功的再现出来；2)Coriolis-Stokes力并不能从根本上改变海洋上层流场结构；3)在全球海洋大部分区域上,Stokes输运的方向和Coriolis-Stokes力引起的海流深度积分输运改变量的方向是不一致的；4)月平均混合层深度积分海流输运改变量的大小和方向是逐月变化的,Coriolis-Stokes力在强涡旋区域能够产生高于其它地方的影响；5)海表面温度和混合层厚度也同时受到Coriolis-Stokes力的影响。最后,我们利用海洋模式POM、海浪模式SWAN以及耦合框架MCT,在前人的工作基础上建立了一套双向完全耦合浪-流耦合模型。此耦合模型被用于进一步探讨波浪驱动的海表面流及其引起的风向海洋能量输入的改变情况。大尺度波浪对海流的作用力,Coriolis-Stokes力,被直接添加于POM的动量方程之中。Coriolis-Stokes力计算所需的波浪参数来自波浪模式SWAN的模拟输出结果。实验结果表明,当浪-流系统处于平衡态时,Coriolis-Stokes力驱动的海表面流的速度能够达到0.001 m/s的量级,最大流速达到0.02 m/s。整个模拟区域内波浪引起的总能量输入达到2.8505×1010w,为总的风能量输入的14%。考虑波浪效应后,整个区域内风能量输入增加了13.96%。更多还原

【Abstract】 This dissertation consists of two parts. The first part concentrates on the influences of ocean surface velocity (current velocity and wave-induced velocity) on the upper ocean phenomana, including wind stress, surface current field, sea surface temperature, air-sea heat flux and boundary layer thickness. The second part puts insight into the effects of large scale wave-induced Coriolis-Stokes forcing on modeling of the upper ocean currents. In order to achieve those research aims in this dissertation, two coupled models are constructed. They are coupled wind-current model (HYCOM-WINDS) and coupled wave-current model (SWAN-POM).By accounting for the effects of ocean surface velocity (wave-induced surface drift velocity and current velocity) on the drag coefficient, the spatial distribution of drag coefficient and wind stress are computed over the global ocean during 1958-2001, using an empirical drag coefficient parameterization formula based on wave steepness and wind speed. The global ocean current field is generated from the Hybrid Coordinate Ocean Model (HYCOM) and the waves from Wavewatch III (WW3). The spatial variability of the drag coefficient and wind stress are analyzed. Preliminary results indicate that, the ocean surface drift velocity exerts an influence on the wind stress, about 5% in average. The results also show that accounting for the effect of the ocean surface velocity on the wind stress can lead to significant improvement in the modeling of ocean circulation and air-sea interaction processes.In additation, A Wind stress-Current Coupled System (WCCS) consisting of the HYbrid Coordinate Ocean Model (HYCOM) and an improved wind stress algorithm based on Donelan et al. (1997) is developed by using the Earth System Modeling Framework (ESMF). The WCCS is applied to the global ocean to study the interactions between the wind stress and the ocean surface currents. In this study, the ocean surface current velocity is taken into consideration in the wind stress calculation and air-sea heat flux calculation. The wind stress that contains the effect of ocean surface current velocity will be used to force the HYCOM. The results indicate that the ocean surface velocity exerts an important influence on the wind stress, which, in turn, significantly affects the global ocean surface currents, air-sea heat fluxes, and the thickness of ocean surface boundary layer. Comparison with the TOGA TAO buoy data, the sea surface temperature from the wind-current coupled simulation showed noticeable improvement over the stand-alone HYCOM simulation.As for investigation of the large scale wave effects on ocean modeling, first, we found a well-defined zone of swell dominance, termed "swell pool", located in the eastern areas of the Pacific by calculating the global distribution of swell index in 2000. The global monthly mean wave transport for each month of 2000 is derived by taking advantage of the ECWMF reanalysis wave products. By comparing the monthly mean wave transport and monthly mean wind field from QUICKSCAT both of 2000, large difference is found between the Stokes transport direction and the wind direction in eastern area of the Pacific, approximately 90°.This result may serve as an evidence for proving the existence of the swell pool in this region. We also found that the sources of swell in eastern tropical areas of the Pacific mainly locate in the corresponding regions of westerlies of southern and northern Pacific, respectively. A calculation area is defined with boundaries lie on 2.5°N and 2.5°S (from 125°W to the western terrestrial boundary of America) to calculate the swell-caused net Stokes transport into the tropical region. Strong relationships are found between the net Stokes transport across the two latitudinal boundaries and wind intensities, for each specific month. Finally, we summarized the main conclusion of this study.Then, Six experiments configured for three different domains:Global Ocean, South China Sea (SCS) and Western North Atlantic Ocean (WNA) respectively, using the Hybrid Coordinate Ocean Model (HYCOM) are designed to investigate effects of the wave-induced Coriolis-Stokes forcing (hereinafter referred to as CSF) on ocean surface phenomena including circulation, temperature and mixing processes. The CSF calculated using wave variables simulated by the Wave WatchⅢ(WW3) model is incorporated into HYCOM as a boundary condition in addition to wind stress. The results indicate:1) HYCOM is capable of reproducing the ocean circulation futures in all the three domains with different horizontal resolution. Main features of currents in SCS and WNA are successfully modeled, such as the well-known SCS upper layer circulation which subjects to the seasonally reversed monsoon system, and the loop current and eddy-shedding in WNA (Gulf of Mexico); 2) CSF does not fundamentally modify the pattern of current profile in the ocean surface mixed-layer; 3) Over most of the Global Ocean, the direction of Stokes transports are different from that of the changes in depth-integrated current transports caused by CSF; 4) The monthly-mean changes in depth-integrated current transports in the mixed-layer is changing month to month in both direction and magnitude and the CSF plays a more significant role in regions of intensive gyre presents, such as the area near Yucatan Channel; and 5) both Sea Surface Temperature (SST) and Mixed-Layer Depth (MLD) are influenced by CSF.Additationaly, The Stokes drift-driven ocean currents and Stokes drift-induced energy rate input to ocean have been investigated in the ideal experiments by taking advantage of a full coupled wave-current system which consists of the ocean component Princeton Ocean Model (POM), wave component Simulating WAves Nearshore (SWAN) and the coupling frame Model Coupling Toolkit (MCT). The Coriolis-Stokes forcing, which is computed by using the wave parameters from SWAN, has been incorporated into the momentum equation of POM as the core coupling process in the coupled system. Experimental results show that, under the steady state, the scale of Coriolis-Stokes forcing-driven current speed is 0.001 and the maximum current speed is 0.02 m/s. The Stokes drift-induced energy rate input into the ocean within the whole experiment domain is estimated as 2.8505×1010 w which is 14% of the direct wind energy rate input. Taking consideration of the Stokes drift effects, the total mechanical energy rate input within the simulation domain is increased by 13.96%.更多还原