Multi-criteria evaluation of wave energy projects on the south-east Australian coast

In the last decade, multiple studies focusing on national-scale assessments of the ocean wave energy resource in Australia identified the Southern Margin to be one of the most energetic areas worldwide suitable for the extraction of wave energy for electricity production. While several companies have deployed single unit devices, the next phase of development will most likely be the deployment of parks with dozens of units, introducing the risk of conflicts within the marine space. This paper presents a geo-spatial multi-criteria evaluation approach to identify optimal locations to deploy a wave energy farm while minimizing potential conflicts with other coastal and offshore users. The methodology presented is based around five major criteria: ocean wave climatology, nature of the seabed, distance to key infrastructure, environmental factors and potential conflict with other users such as shipping and fisheries. A case study is presented for an area off the south-east Australian coast using a total of 18 physical, environmental and socio-economic parameters. The spatial restrictions associated with environmental factors, wave climate, as well as conflict of use, resulted in an overall exclusion of 20% of the study area. Highly suitable areas identified ranged between 11 and 34% of the study area based on scenarios with varying criteria weighting. By spatially comparing different scenarios we identified persistence of a highly suitable area of 700 km2 off the coast of Portland across all model domains investigated. We demonstrate the value of incorporation spatial information at the scale relevant to resource exploitation when examining multiple criteria for optimal site selection of Wave Energy Converters over broad geographic regions.

Experimental investigation on low-temperature fatigue crack propagation in offshore structural steel A131 under random sea ice loading

An apparatus of low-temperature controlling for fatigue experiments and its crack measuring system were developed and used for offshore structural steel A131 under conditions of both low temperature and random sea ice. The experimental procedures and data processing were described, and a universal random data processing software for FCP under spectrum loading was written. Many specific features of random ice-induced FCP which differed with constant amplitude FCP behaviours were proposed and temperature effect on ice-induced FCP was pointed out with an easily neglected aspect in designing for platforms in sea ice emphasized. In the end, differences of FCP behaviours between sea ice and ocean wave were presented.

Depth inversion in coastal water based on SAR image of waves

Wave-number spectrum technique is proposed to retrieve coastal water depths by means of Synthetic Aperture Radar (SAR) image of waves. Based on the general dispersion relation of ocean waves, the wavelength changes of a surface wave over varying water depths can be derived from SAR. Approaching the analysis of SAR images of waves and using the general dispersion relation of ocean waves, this indirect technique of remote sensing bathymetry has been applied to a coastal region of Xiapu in Fujian Province, China. Results show that this technique is suitable for the coastal waters especially for the near-shore regions with variable water depths.

合成孔径雷达提取海面风、浪信息研究

传统海洋测量方法例如岸基观测站、船只和浮标等方式只能对海面进行单点观测，存在很多不足之处：观测点少，只能获得有限的点的资料，无法得到大范围的海面信息；费用较高，无法大范围的密集观测；传统方法受天气影响较大，无法长时间的连续观测；星载合成孔径雷达能全天候、全天时、高分辨率对海面成像，能实现多波段、多极化、多视角得观测海面，提供大范围、高精度的实时动态海面信息。同时，这种全天候、全天时和高分辨率观测海洋的优势是可见光和红外传感器所没有的。总之研究如何从SAR影像中有效地获取海面信息具有重要的科学和实用意义。 自从1978年Seasat卫星发射以来SAR图像就广泛的应用于海洋要素的反演如海面风场、波高、平均周期。其中对海面风场的反演研究的最多，一般的方法是首先对SAR图像进行快速傅立叶变换得到SAR图像谱，通过图像谱的峰值信息能够得到具有180°模糊的风向，利用SAR图像的条纹或者浮标等外部信息来消除180°模糊确定风向，其次把风向和图像的正交后向散射截面数值(NRCS)带入经验函数CMOD4通过迭代计算得到风速。这种方法得到的海面风场需要外部信息的辅助，不利于大范围的业务化的反演海面风场。因此本文试图直接通过SAR图像来反演海面风场而不利用其他外部信息的帮助。2002年3月1日发射的ENVISAT卫星所获得的ASAR图像具有不同于ERS系列的SAR图像的新特点：不同入射角的情况下获得ASAR图片、双极化数据以及可以获得更宽的带幅的图像。双极化数据可以同时地提供同极化和交错极化的影像，两种极化的数据能够增加分辨目标的能力和提供目标更多的信息，这方面的优势也使得利用双极化的数据来消除SAR图像反演风场中的180º模糊问题提供了可能。本文推导了利用双极化的ASAR图像反演海面风场的新函数，该函数是在同极化和交错极化函数的基础上推导出来的，有效的消除了只用一副ASAR图片反演风场所固有的180º模糊现象。风速和风向的反演结果与Quikscat数据之间的均方根误差分别为0.53 m/s和2.21º。该方法与传统方法的比较可以看出新方法与浮标数据以及Quikscat数据符合的更好。 利用SAR图像来反演海浪的波高也是一个研究的比较多的领域。比较传统的方法是由SAR图像得到的海浪谱计算出波高，目前国际上比较流行的SAR图像反演海浪谱的模式有两种：一种是Hasselmann（1991）提出的在Max－Planck Institute（MPI）发展起来的方法，Hasselmann（1996）进行了改进和完善。另一种是Mastenbroek和de Valk（2000）提出的半参数化反演方法。这两种方法的最主要的缺点就是需要引进外部信息(WAM模式结果或者散射计的风的信息)来消除图像所固有的180°方向模糊问题。而本文应用的经验函数方法(CWAVE)不需要引进任何外部信息而直接得到海浪的重要参数－有效波高(Hs)，输入该经验函数的参数主要有：波模式图像的雷达截面、图像方差以及由SAR谱得到的20个参数。这些参数的选择是通过逐步回归方法进行筛选的。CWAVE经验函数的系数是通过6000幅全球分布的ERS-2波模式的图像谱拟合同时同地点的WAM模式结果得到的。利用CWAVE经验函数反演了1998年9月到2000年11月两年多的全球接近一百万的ERS-2 SAR图像的有效波高，利用NOAA浮标数据对反演结果进行了验证，他们之间的相关系数为0.83, 均方根误差为0.61m，偏差为0.02 m；反演结果也与欧洲中长期预报中心(ECMWF)的ERA-40有效波高资料和高度计资料进行了比较，结果表明该方法是通过SAR图像反演Hs的一种有效方法。 SAR的反演结果也应用于有效波高的非线性统计分布的研究。结合动力学和随机统计学原理推导了海面高度、波高和有效波高的非线性统计分布，同时利用了NOAA浮标数据、华师大的波高数据以及SAR的有效波高数据分别对推导出的非线性统计分布函数进行了检验。 SAR的结果也用来反演新的风浪成长关系： ，与已有的风浪成长关系的比较表明该成长关系与已有的结果比较一致。

星载散射计海浪参数提取方法研究

海浪是重要的海洋动力环境参数之一,迄今为止，合成孔径雷达是唯一测量海浪谱的传感器，然而，由于它存在方位波数的截止和能量短缺，限制了其应用。卫星高度计可以测量全球有效波高，但其二维空间分辨率低，其应用也受到了限制。因此，发展一个能够全天候全天时测量海浪参数的有效方法迫在眉睫。 本论文希望利用散射计提取波浪参数,主要研究工作如下： 1、利用二尺度理论模拟了涌浪对C-波段后向散射系数的影响，并与前人在L-波段 和 Ku-波段模拟的结果进行了比较，验证了涌浪对雷达后向散射截面的影响随雷达频率增加而减小，同样也随入射角增大而减小。 2、根据浮标和散射计匹配的数据发现，当海浪参数和雷达入射角给定后，雷达后向散射截面同方位角的关系显示二阶余弦函数关系，为此建立了一种BP神经网络波浪参数反演模式。 3、分别发展了ERS卫星和QuikSCAT卫星散射计资料反演海浪参数的方法，利用NDBC浮标数据分别对它们反演的波浪参数进行了验证。并发现风浪占优势时反演有效波高的结果好于涌浪占优势；C-波段反演有效波高的结果要好于Ku波段,且在Ku波段，水平极化好于垂直极化；波陡反演的结果不受海况影响。 关键词：散射计，风浪，涌浪，有效波高，平均周期，波陡，神经网络

干涉合成孔径雷达海浪遥感理论与应用研究

干涉合成孔径雷达 (Interferometric Synthetic Aperture Radar，InSAR) 是以合成孔径雷达复数据提取的相位为信息源获取地表三维信息和海表散射体运动信息的新型微波成像雷达。 InSAR通过两幅天线同时观测 (单轨模式)，或两次近平行的观测 (重复轨道模式)，获取地面或海面同一景观的复图像对。20世纪90年代以来，InSAR陆地和海洋研究成为微波遥感的热点，广泛应用于地表变形监测、南极冰流测量、地面或海面慢速运动目标检测等领域。 近年来，国际上逐渐应用机载顺轨或交轨干涉合成孔径雷达进行海表面流速测量以及海面波成像机制研究。相对于传统单天线合成孔径雷达 (Synthetic Aperture Radar, SAR)，双天线干涉合成孔径雷达 (InSAR) 测量海表面波有着独特的优势： (1) InSAR复图像的相位近似正比于海面散射体的径向速度，这种内在的成像机制提供了直接测量海表面动态运动的机会。 (2) 真实孔径雷达调制传递函数几乎对InSAR相位图像没有影响，而对传统SAR图像影响较大。 基于干涉合成孔径雷达测量海浪的优势，本文做了一些干涉合成孔径雷达海浪遥感理论与应用研究工作，主要内容大致可归纳如下： (1)基于新建立的顺轨干涉合成孔径雷达 (Along-Track Interferometric Synthetic Aperture Radar，ATI-SAR) 相位谱与海浪谱之间的非线性映射关系，通过数值模拟研究了不同雷达参数和海况参数对应的ATI-SAR相位谱。数值模拟结果表明：距离速度比率、雷达入射角、天线间距和有效波高和波长比率是影响ATI-SAR海浪成像的重要因素。进一步，利用机载X波段水平极化相位图像和机载C波段水平极化相位图像谱结合方向波骑士浮标测量的海浪方向谱验证了ATI-SAR相位谱与海浪谱之间的非线性映射关系。结果显示用前向映射关系计算的相位谱与实际观测的相位谱较为一致，二者相关系数总体大于0.6，而且对成像非线性不敏感. (2)建立了包含海表面高度和速度聚束的交轨干涉合成孔径雷达 (Across-Track Interferometric Synthetic Aperture Radar，XTI-SAR) 涌浪干涉相位模型，得到了涌浪成像的解析表达式，进一步研究了XTI-SAR沿方位向传播的涌浪成像机制。定义二次谐波振幅与基波振幅比率来表征成像非线性，通过比较XTI-SAR和ATI-SAR相位的二阶调和分量，分析不同海况和干涉SAR参数情况下的数值模拟，结果表明：当速度聚束弱时，XTI-SAR相位比ATI-SAR相位具有较强的非线性，ATI-SAR比XTI-SAR更适合测量海浪。当速度聚束强时，XTI-SAR相位比ATI-SAR相位具有较弱的非线性，XTI-SAR比ATI-SAR更适合测量海浪。 (3)基于包含海表面高度和速度聚束的交轨干涉合成孔径雷达 (XTI-SAR) 涌浪干涉相位模型，结合多维高斯变量的特征函数方法建立了新的XTI-SAR相位谱与海浪谱非线性积分变换。新积分变换不同于Bao (1999) 建立的积分变换，两者形式上区别在于新积分变换中包含了长波径向轨道速度一阶倒数项。数值模拟显示：通常情况下，长波径向轨道速度一阶倒数项不能忽略。进一步，我们针对不同雷达参数和海况结合新非线积分变换对XTI-SAR海浪成像进行了数值模拟，结果表明：同顺轨干涉合成孔径雷达 (ATI-SAR) 海浪成像一致，距离速度比率 和有效波高与波长比率 是影响XTI-SAR海浪成像的重要因子。 (4)基于新的ATI-SAR相位谱与海浪谱之间的非线性映射关系，发展了利用ATI-SAR相位图像反演海浪方向谱的参数化反演模式，并由此得到海浪波长、波向和有效波高。反演结果与现场浮标观测结果比较一致。相对于其它反演模式，参数化反演模式的优点在于：(1) 不需要任何附加信息如初猜海浪谱、散射计提供的风速风向等信息。 (2) 不需要对相位图像进行辐射定标，可以由反演的海浪谱直接计算有效波高。(3) 反演结束后还可以得到成像区域的局地风速信息。因此，参数化反演模式可以实现风、浪信息的联合反演。

Site level cost benefit analysis of renewable energy in the near-shore environment

Senior thesis written for Oceanography 445

The effect of doubled CO2 and model basic state biases on the monsoon-ENSO system. II: Changing ENSO regimes

Integrations of a fully-coupled climate model with and without flux adjustments in the equatorial oceans are performed under 2×CO2 conditions to explore in more detail the impact of increased greenhouse gas forcing on the monsoon-ENSO system. When flux adjustments are used to correct some systematic model biases, ENSO behaviour in the modelled future climate features distinct irregular and periodic (biennial) regimes. Comparison with the observed record yields some consistency with ENSO modes primarily based on air-sea interaction and those dependent on basinwide ocean wave dynamics. Simple theory is also used to draw analogies between the regimes and irregular (stochastically forced) and self-excited oscillations respectively. Periodic behaviour is also found in the Asian-Australian monsoon system, part of an overall biennial tendency of the model under these conditions related to strong monsoon forcing and increased coupling between the Indian and Pacific Oceans. The tropospheric biennial oscillation (TBO) thus serves as a useful descriptor for the coupled monsoon-ENSO system in this case. The presence of obvious regime changes in the monsoon-ENSO system on interdecadal timescales, when using flux adjustments, suggests there may be greater uncertainty in projections of future climate, although further modelling studies are required to confirm the realism and cause of such changes.

Granular flow in the marginal ice zone

The region of sea ice near the edge of the sea ice pack is known as the marginal ice zone (MIZ), and its dynamics are complicated by ocean wave interaction with the ice cover, strong gradients in the atmosphere and ocean and variations in sea ice rheology. This paper focuses on the role of sea ice rheology in determining the dynamics of the MIZ. Here, sea ice is treated as a granular material with a composite rheology describing collisional ice floe interaction and plastic interaction. The collisional component of sea ice rheology depends upon the granular temperature, a measure of the kinetic energy of flow fluctuations. A simplified model of the MIZ is introduced consisting of the along and across momentum balance of the sea ice and the balance equation of fluctuation kinetic energy. The steady solution of these equations is found to leading order using elementary methods. This reveals a concentrated region of rapid ice flow parallel to the ice edge, which is in accordance with field observations, and previously called the ice jet. Previous explanations of the ice jet relied upon the existence of ocean currents beneath the ice cover. We show that an ice jet results as a natural consequence of the granular nature of sea ice.

Circulação recente de sedimentos costeiros nas praias de santos durante eventos de tempestades: Dados para a gestão de impactos físicos costeiros

The beachs of Santos are situated in Santos Bay, central portion of paulista coast, in São Paulo state. This beachs are frequently affected by cold fronts with winds and currents from the South. These fronts are responsible for the removal and transport of sediments (sand) in Santos beaches. In order to quantify this sedimentation the channels of Santos were analysed, due to their function as box colectors of sediments during storm events. The channels are filled by sands, which volume in channels 1 to 6 was estimated, by using the length, width and height of sand sedimented in the channels, in the event of 22-27 april 2005. The chanels 2, 3 and 1 presented the larger volumes of sands, confirming that the central and SW portion of the beaches of Santos present higher levels of sedimentation or re-sedimentation. That is due to the transport by ocean waves and currents and currents from the Channel of the Port of Santos. This central portion suffer invasion of marine water over street and buildings, caracterizated of geological rise area.

Modelagem e análise de desempenho de sistema para geração de energia elétrica através de ondas marítimas.

Mediante a crescente necessidade de aumento na oferta de energia elétrica devido à constante elevação na demanda mundial, esta dissertação avalia o desempenho de um sistema conversor de energia de ondas marítimas em energia elétrica. O sistema em análise é o de coluna de água oscilante com turbina de dupla ação instalado na costa. Utiliza-se um modelo regular de ondas como perturbação à dinâmica de uma câmara semi-submersa gerando fluxo de ar através de uma turbina à ar de dupla ação. O sistema final é não linear e com parâmetros variantes no tempo. A dissertação investiga possibilidades para o aumento do rendimento da turbina em diferentes condições de mar através do método de simulação numérica. Após a modelagem física e matemática do sistema escolhido, inicia-se a síntese de um controlador proporcional derivativo para controle da pressão de ar na turbina em torno da pressão ideal de trabalho da mesma. A análise inclui o comparativo entre os resultados do sistema com e sem controlador e a avaliação de robustez utilizando ondas com amplitude variável. O trabalho apresenta ainda propostas de otimização do sistema para trabalhar em condições similares a região de Pecém no Brasil. Pelos resultados obtidos nas simulações, conclui-se que o rendimento e a robustez do sistema podem melhorar utilizando um sistema controlado. O rendimento do sistema poderá ainda ser otimizado para a região de instalação.

A Delay Vector Variance based marker for an output-only assessment of structural changes in tension leg platforms

Although aspects of power generation of many offshore renewable devices are well understood, their dynamic responses under high wind and wave conditions are still to be investigated to a great detail. Output only statistical markers are important for these offshore devices, since access to the device is limited and information about the exposure conditions and the true behaviour of the devices are generally partial, limited, and vague or even absent. The markers can summarise and characterise the behaviour of these devices from their dynamic response available as time series data. The behaviour may be linear or nonlinear and consequently a marker that can track the changes in structural situations can be quite important. These markers can then be helpful in assessing the current condition of the structure and can indicate possible intervention, monitoring or assessment. This paper considers a Delay Vector Variance based marker for changes in a tension leg platform tested in an ocean wave basin for structural changes brought about by single column dampers. The approach is based on dynamic outputs of the device alone and is based on the estimation of the nonlinearity of the output signal. The advantages of the selected marker and its response with changing structural properties are discussed. The marker is observed to be important for monitoring the as- deployed structural condition and is sensitive to changes in such conditions. Influence of exposure conditions of wave loading is also discussed in this study based only on experimental data.