Ocean tides for satellite geodesy

Abstract

Spherical harmonic tidal solutions have been obtained at the frequencies of the 32 largest luni‐solar tides using prior theory of the author. That theory was developed for turbulent, nonglobal, self‐gravitating, and loading oceans possessing realistic bathymetry and linearized bottom friction; the oceans satisfy no‐flow boundary conditions at coastlines. In this theory the eddy viscosity and bottom drag coefficients are treated as spatially uniform. Comparison of the predicted degree‐2 components of the Mf, PI, and M2 tides with those from numerical and satellite‐based tide models allows the ocean friction parameters to be estimated at long and short periods. Using the 32 tide solutions, the frequency dependence of tidal admittance is investigated, and the validity of sideband tide models used in satellite orbit analysis is examined. The implications of admittance variability for oceanic resonances are also explored. By extending the theory to include a second constraint derived from tide observations or data‐constrained tide models, it is possible to assess those models from a fluid dynamic perspective. One general conclusion from such exercises is that the large higher‐degree admittances of current short‐period tide models are dynamically incompatible with their degree‐2 admittances. Eventually it may prove possible to produce dynamically sound, observationally consistent tide models by combining the author's tide theory with satellite orbit determination.     

Reconstruction of eddies by assimilating satellite altimeter data into Princeton Ocean Model

An optimal interpolation assimilation model for satellite altimetry data is developed based on Princeton Ocean Model (POM), which is applied in a quasi-global domain, by the method of isotropic correlation between sea level anomaly (SLA) and sea temperature anomaly. The perfor- mance of this assimilation model is validated by the modeled results of SLA and the current patterns. Comparisons between modeling and satellite data show that both the magnitudes and distribution patterns of the simulated SLA are improved by assimilation. The most signiˉcant improvement is that meso-scale systems, e.g., eddies, are well reconstructed. The evolution of an eddy located in the northwest Paciˉc Ocean is traced by using the assimilation model. Model results show that during three months the eddy migrated southwestward for about 6 degrees before merging into the Kuroshio. The three dimensional structure of this eddy on 12 August 2001 is further analyzed. The strength of this warm, cyclonic eddy decreases with the increase of depth. The eddy shows di?erent horizontal patterns at di?erent layers, and the SLA and temperature ˉelds agree with each other well. This study suggests that this kind of data assimilation is economic and reliable for eddy reconstruction, and can be used as a promising technique in further studies of ocean eddies as well as other ˉne circulation structures.     

我国卫星海洋遥感监测

卫星遥感是20世纪50年代发展起来的一种新技术.运用这项新技术,可以对浩瀚的海洋进行实时、全方位的立体监测,长期获得稳定可靠的海洋观测资料.本文介绍了我国卫星海洋遥感监测现状,包括对海上台风、海洋赤潮、海冰、溢油、海温、海岸带等方面的监测,还简要介绍了我国海洋卫星和海洋卫星遥感监测的未来发展.     

基于卫星遥感数据的全球表层流场反演重构

利用2000—2008年的卫星高度计资料和QuikSCAT风场资料,反演了全球的海表的地转流和Ekman流,将两者合成后生成了0.5°×0.5°的逐周全球表层流产品。在计算Ekman流的时候,引入了权重函数,改进了Lagerloef方法中Ekman流在25°S和25°N上的不连续问题。分析表明:卫星资料反演的流产品能够反映出海表流场的特征,将其分别与TAO观测和SCUD流产品进行定量化的比较显示,所得流产品具有较高的反演精度和可信度,说明改进的方法是有效的。     

基于卫星遥感海面温度数据的海洋锋分海区分析方法

为了能够合理准确地描述海洋锋特征体系以及锋区本身的各种结构要素,提出了一种中国近海海洋锋分海区分析方法:首先,在对中国近海27条典型海洋锋的时空分布特征和季节演变系统归纳的基础上,基于多年卫星遥感海面温度数据锋面出现频率图,得出中国近海海区锋面系统划分方法;然后,利用日益更新的高时空分辨率卫星遥感海面温度数据,对各划分海区内海洋锋时空分布特征进行分析,调整纠正以往锋面系统分析的偏差或空缺,对中国近海锋面系统进行补充完善,为中国近海各锋面系统特征参数的规范化分析和准确的特征描述奠定基础。该方法对完善我国近海锋面系统研究具有长远的应用价值,对形成中远海及世界大洋海洋锋时空分布特征具有指导作用。     

基于卫星遥感数据的全球表层流场反演重构

利用2000~2008年的卫星高度计资料和QuikSCAT风场资料,反演了全球的海表的地转流和Ekman流,将两者合成后生成了0．5°×0．5°的逐周全球表层流产品。在计算Ekman流的时候,引入了权重函数,改进了Lagerloef方法中Ekman流在25°S和25°N上的不连续问题。分析表明：卫星资料反演的流产品能够反映出海表流场的特征,将其分别于TAO观测和SGUD流产品进行定量化的比较显示,所得流产品具有较高的反演精度和可信度,说明改进的方法是有效的。     

Mesoscale surface circulation and variability of Southern Indian Ocean derived by combining satellite altimetry and drifter observations

High resoultion Eulerian mean velocity field has been derived by combining the satellite tracked surface drifter data with satellite altimetry and ocean surface winds. The drifter data used in this study includes Argos and surface drifter data from Global Drifter Program. Maps of Sea Level Anomaly(MSLA) weekly files with a resolution of(1/3)° in both Latitude and Longitude for the period 1993–2012 have been used. The Ekman current is computed using ocean surface mean wind fields from scatterometers onboard ERS 1/2,Quikscat and ASCAT. The derived mean velocity field exhibits the broad flow of Antarctic Circumpolar Current with speeds up to 0.6 m/s.Anomalous field is quite significant in the western part between 20° and 40°E and in the eastern part between 80°E and 100°E with velocity anomaly up to 0.3 m/s. The estimated mean flow pattern well agrees with the dynamic topography derived from in-situ observations. Also,the derived velocity field is consistent with the in-situ ADCP current measurements. Eddy kinetic energy illustrates an increasing trend during 1993–2008 and is in phase coherence with the Southern Annular Mode by three month lag. Periodic modulations are found in the eddy kinetic energy due the low frequency Antarctic Circumpolar Wave propagation.     

Impact on oceanic dynamics from assimilation of satellite surface height anomaly data into the Hybrid Coordinate Ocean Model Ocean Model (HYCOM) over the Atlantic Ocean

Observed along-track data of sea surface height anomalies (SSHAs) over the Atlantic Ocean from the Jason-1 and Jason-2 satellites were assimilated into the Hybrid-Coordinate Ocean Model (HYCOM) with the Ensemble Optimal Interpolation scheme (EnOI). The impact of assimilation of SSHA with focus on oceanic dynamics was investigated. Time series of analyzed and forecasted values were compared with a model free run with the same forcing but without assimilation. In addition, the results were compared with an independent run, the so-called HYCOM + NCODA analysis from the US Navy. The study shows that the assimilation technique with some modifications allowed substantial improvement in the 24 h ocean prediction by reducing the forecast errors in comparison with the free run. It is also shown that the analyzed sea surface fields contain mesoscale and synoptic variability, which are poorly seen in the free run.     

Inter-comparison of model-predicted wave heights with satellite altimeter measurements in the north Indian Ocean

A numerical model based on a wind-wave energy transport formulation of Toba is developed to generate hindcast wave height data for the equatorial and the north Indian Ocean, which is otherwise a data-sparse region. The intercomparison between model-predicted wave heights for three years (1987–1989) obtained utilising analysed surface wind fields' data, and model grid averaged GEOSAT Altimeter significant wave height data showed moderate match, particularly for H_S greater than 1 m.     

基于漂流浮标的南大洋卫星高度计有效波高研究

随着技术的进步和数据处理方法的完善,经过修正的卫星高度计数据已获得普遍认可.但在南大洋缺少波浪现场数据,卫星高度计在极端恶劣气候条件下获得数据的准确度仍受到一定程度的质疑.中国于2020年第36次南极考察中,在南大洋布放了一套感应耦合漂流浮标,可提供可靠的南大洋现场波浪数据.本文利用该漂流浮标2020年1月27日至9月...     

南大洋太平洋扇区中尺度涡旋的统计特性及其变化

中尺度涡旋在南大洋海洋动力学中具有重要地位,其对气候变化的响应表现也引起了海洋学家与气候学家的广泛关注。本文利用涡动动能与涡旋自动探测技术两种方法对南大洋太平洋扇区的涡旋特性及其变化进行了分析。与前人结果相一致的是,高值的涡动动能主要集中在南极极锋海区,并且自西向东逐渐减弱。在过去的20年里,涡动动能在太平洋扇区的显著增强也集中在中西部海域,这里也是南极绕极流斜压性较强的海域。涡旋统计特性揭示了涡动动能的空间分布及其年际变化主要归因于涡旋振幅与旋转速度,而并非涡旋个数或者涡旋半径。这些结果进一步确认了对应于南半球环状模正位相的绕极西风异常改变了南大洋的涡旋特性,从而表现出涡旋活跃性增强。     

基于MTSAT卫星遥感的中国海及西北太平洋海域海表温度日增温研究

Hourly sea surface temperature(SST) observations from the geostationary satellite are increasingly used in studies of the diurnal warming of the surface oceans. The aim of this study is to derive the spatial and temporal distribution of diurnal warming in the China seas and northwestern Pacific Ocean from Multi-functional Transport Satellite(MTSAT) SST. The MTSAT SST is validated against drifting buoy measurements firstly. It shows mean biases is about –0.2°C and standard deviation is about 0.6°C comparable to other satellite SST accuracy. The results show that the tropics, mid-latitudes controlled by subtropical high and marginal seas are frequently affected by large diurnal warming. The Kuroshio and its extension regions are smaller compared with the surrounding regions. A clear seasonal signal, peaking at spring and summer can be seen from the long time series of diurnal warming in the domain in average. It may due to large insolation and low wind speed in spring and summer, while the winter being the opposite. Surface wind speed modulates the amplitude of the diurnal cycle by influencing the surface heat flux and by determining the momentum flux. For the shallow marginal seas, such as the East China Sea, turbidity would be another important factor promoting diurnal warming. It suggests the need for the diurnal variation to be considered in SST measurement, air-sea flux estimation and multiple sensors SST blending.     

海洋激光荧光雷达海面油膜种类鉴别研究

海洋激光雷达在探测海面油荧光方面的应用 ,受到广泛重视。海洋激光荧光雷达是以物质荧光谱理论为基础 ,将荧光技术应用于海面油膜检测领域。本文介绍了激光荧光原理 ,青岛海洋大学海洋激光雷达的基本结构和工作过程 ,以及该套系统进行海面油膜种类鉴别的使用方法和适用范围。通过实验证明 ,该套系统性能可靠 ,测量值稳定 ,能够进行一定程度上的油荧光测量。提出采用荧光强度 4 35 / 380 ,4 35 / 5 0 0 ,4 35 / 5 5 0 ,3个比值作为油样荧光特性的描述值进行油种鉴别。相对其他的鉴别方法 ,三比值法无须配置溶液 ,适于现场测量。根据系统响应情况提取的特征值不但更有针对性 ,而且由于特征值数量多 ,对荧光谱分布曲线的描述更加准确。     

AQUA 卫星的MODIS和AMSR-E 反演的 印度洋北部海域海表温度特征对比分析

以印度洋北部海域为研究区域,分别从地理位置、温度曲线和反演精度3 个方面对AQUA 卫星上的MODIS 和 AMSR-E反演的海表温度特征进行了对比分析。其主要特征表现为MODIS SST 与AMSR-E SST 之间的差异随纬度变化较为 明显;在近岸区域,AMSR-E SST无法获得准确的海表面温度;MODIS SST 与AMSR-E SST 之间的差异随温度而不同;在本 次研究中,AMSR-E SST 反演精度总体优于MODIS SST。本次研究结果对利用热红外遥感和被动微波遥感进行海洋表面温度 的定量反演具有重要的参考价值。     

一种智能水下机器人进行大范围海洋环境监测的方案与实验

采用智能水下机器人进行海洋环境的立体监测具有监测范围广,自主性强的特点。本文在探讨世界各国采用智能水下机器人进行海洋环境监测的情况的基础上,介绍了自主研发的智能水下机器人海洋大范围环境数据的自主采集系统,其主要优点是：相对于其他机器人,可实现“大范围” 海洋环境数据的采集;相对于固定式浮标,可实现海洋环境数据的“自主”采集。并给出了自主采集流程和软件分层递阶体系结构。在真实海域中,采用智能水下机器人,进行了国内首次大范围环境数据采集实航实验。实验结果表明采用智能水下机器人进行海洋环境的立体监测是切实可行的。     

Offshore geotechnical instrumentation

This brief discussion of instrumentation for geotechnical engineering applies to fixed bottom supported structures, as well as to sea floor connected floating structures, pipelines, and buoys. At the outset, it is important to recognize the interaction among: 1) local soil conditions at the site of a structure, 2) the structural configuration itself, and 3) the sampling and testing techniques that might be used. The interaction occurs, of course, in the sense that the types of soils that occur at sites certainly influence the techniques of soil sampling and testing that are appropriate. Further, the local soil conditions can influence the selection of the configuration of the structure and foundation system. Soil provides a basic foundation support for all of these sttuctures.     

提升国家海洋技术总体实力推进我国海洋强国建设

本文讨论了成立国家海洋技术中心对我国海洋技术发展的影响。分析了目前我国海洋技术总体实力存在的主要问题。为提升国家海洋技术总体实力，推进我国海洋强国建设，本文提出了相应的建议。