An Improved Calibration of Satellite Altimetric Heights Using Tide Gauge Sea Levels with Adjustment for Land Motion   总被引：2，自引：0，他引：2  

Gary T. Mitchum 《Marine Geodesy》2000,23(3):145-166

Several major improvements to an existing method for calibrating satellite altimeters using tide gauge data are described. The calibration is in the sense of monitoring and correcting temporal drift in the altimetric time series, which is essential in efforts to use the altimetric data for especially demanding applications. Examples include the determination of the rate of change of global mean sea level and the study of the relatively subtle, but climatically important, decadal variations in basin scale sea levels. The improvements are to the method described by Mitchum (1998a), and the modifications are of two basic types. First, since the method depends on the cancellation of true ocean signals by differencing the altimetric data from the tide gauge sea level time series, improvements are made that produce a more complete removal of the ocean signals that comprise the noise for the altimetric drift estimation problem. Second, a major error source in the tide gauge data, namely land motion, is explicitly addressed and corrections are developed that incorporate space-based geodetic data (continuous GPS and DORIS measurements). The long-term solution, having such geodetic measurements available at all the tide gauges, is not yet a reality, so an interim solution is developed. The improved method is applied to the TOPEX altimetric data. The Side A data (August 1992?February 1999) are found to have a linear drift component of 0.55 + / 0.39 mm/yr, but there is also a significant quadratic component to the drift that is presently unexplained. The TOPEX Side B altimeter is estimated to be biased by 7.0 + / 0.7 mm relative to the Side A altimeter based on an analysis of the first 350 days of Side B data.  相似文献   

Mean Sea Level Variation in the South China Sea from Four Decades of Tidal Records in Hong Kong     

H. Baki Iz  C. K. Shum 《Marine Geodesy》2000,23(4):221-233

  相似文献   

印尼8.7、 8.5级巨震对云南地区地震活动的远震触发分析   总被引：5，自引：0，他引：5  

李纲  刘杰  郭铁栓 《地震》2005,25(4):49-57

在收集整理印尼8.7、 8.5级巨震活动特点基础上, 分析了这两次巨震对云南地区地震活动的远震触发特征。 依据腾冲、 昆明两个台站的数字波形资料, 对这两次巨震的触发特点进行了分析。 认为云南地区2004年12月26日后地震活动的显著增强, 是由印尼8.7级巨震的长周期面波触发引起的。 8.5级地震后, 云南地区地震活动没有引起触发, 主要原因是8.7级地震已引起相关地震活动, 短期内断层不足以积累使其破裂的能量所致。 远震触发的地区与高热流地区一致。  相似文献   

电子潮汐表的开发与应用   总被引：3，自引：0，他引：3  

张学宏  刘金芳  郝培章  修义瑞 《海洋预报》2005,22(2):72-76

针对目前国内外港口潮汐预报的应用现状,为适应电子化、信息化的需要,以提高资料的利用价值、提高用户的工作效率为目的,我们开发研制了电子潮汐表系统．本文从电子潮汐表的定义着手介绍了电子潮汐表系统开发和应用,并提出了需要完善的内容．电子潮汐表的开发完成不仅具有一定的经济效益,而且带来明显的军事应用价值．  相似文献   

Tide-induced flow signature in rip currents on a meso-macrotidal beach     

《Ocean Modelling》2014

On rip-channelled beaches, intense rip currents are driven by waves due to alongshore variations in breaking-induced wave energy dissipation. This study addresses for the first time the potential development of tidal currents superimposed onto the wave-driven circulation. This phenomenon is observed on a rip-channelled meso-macrotidal beach (Biscarrosse, SW France). Field measurements show 20 to 45% stronger mean rip velocities during ebb than during flood. Numerical experiments reveal that this asymmetry is the signature of tidal currents developing over the rip channel morphology. This asymmetry is found to increase roughly linearly with increasing tidal range. These results are significant to beach safety and lifeguarding and stimulate further numerical exercises.  相似文献   

从新疆地区主余震活动看地震静态应力触发模型   总被引：1，自引：0，他引：1       下载免费PDF全文

姜辉  邓志辉  王海涛  王琼  路星 《地震地质》2011,33(3):586-601

选取新疆地区1970年以来15次MS6.0以上地震作为源地震,MS4.0以上余震作为目标余震,对地震静态应力触发模型进行检验分析.结果表明,地震静态应力触发模型在新疆地区存在问题,80％的源地震发生后,其△CFS正区目标余震数量少于负区目标余震数量;33％的源地震发生后,其正区目标余震数量远少于负区目标余震数量(前者不...  相似文献   

Effects of waves on the initiation of headland-associated sandbanks     

Nicolas Guillou  Georges Chapalain 《Continental Shelf Research》2011,31(11):1202-1213

Linear sandbanks appear in the lee of coastal headlands where the hydrodynamics are dominated by strong tidal currents and the seabed is characterized by an abundance of sands. They may develop as symmetrical sandbanks on either sides of the headland or as an unique banner bank. The present study numerically investigates the combined effects of waves and tide on the initial development of headland-associated sandbanks. A morphological model based on the coupling of the wave propagation module SWAN (Simulating WAves Nearshore) with the three-dimensional circulation module COHERENS (COupled Hydrodynamical-Ecological model for REgioNal and Shelf seas) is applied to an idealized Gaussian shaped headland for waves conditions varying in heights and directions at the offshore boundary. The coupling considers the effects of the interactions between the wave and current bottom boundary layers, namely the enhanced levels of turbulence near the bottom and the increase of the total bottom shear stress. Waves substantially modify the initial development of sandbanks formed by suspension narrowing their width and reorienting them along the side of the headland. They weakly impact the morphogenesis of sandbanks by bedload favoring on a short-time scale the growth of symmetric circular-shaped features and a central depositional spit prolonging the headland tip. Waves of transverse directions toward the tip of the headland contribute to the initiation by suspension of a well-developed feature in the headland side of low energy limiting the seabed evolution in the exposed area.  相似文献   

地壳中的应力场及一些诱震因素     

曾心传 《大地测量与地球动力学》1997,(1)

把地球考虑为在径向上由ｎ层具有不同物理—力学性质的物质所组成的球体，由此出发，推导了计算地壳中由地球自重、匀速自转、天体引力、地球自转速度变化所产生的位移场和应力场的公式。对由地壳和地幔以下物质所组成的二层体情形进行了详细推演，数值计算表明：作为诱震因素，天体引力特别是月亮对地球的引力似乎比地球自转速度变化所起的作用更大  相似文献   

中国及邻区地震的天文潮汐触发特征研究——附加潮汐应力对发震断层的作用模式及其应用     

吴小平 《天文研究与技术》2002,(1)

本文在潮汐应力、构造应力、地震断层和岩石破裂滑动理论的基础上 ,建立了潮汐应力对地震断层作用的力学模式 ,该模式将潮汐应力与地震应力作用相结合 ,描述了沿地震主压应力和地震主张应力方向的附加潮汐应力对发震断层的力学作用方式 ,从而切入潮汐应力触发地震的物理机制 ,认为潮汐对地震的触发作用在实质上归结为潮汐应力对地震断层的促滑作用 ,这种促滑作用分增压型和减压型。在此模式基础上 ,对中国大陆及邻区的不同类型地震的潮汐触发性进行了研究 ,内容包括 :计算了中国及邻区一千多个地震震源处沿主压应力P轴和主张应力T轴方向的附加潮汐应力分量 ,分析了这些量对发震断层的作用方式 ,按纬度区域统计了受到潮汐应力促滑作用的发震断层类型以及它们与潮汐应力作用方式的关系 ,得到了如下结论 :受到潮汐应力促滑作用的发震断层的比例随区域纬度增加有减小趋势 ,其中 ,走滑型断层的比例在低纬区较大 ,而倾滑斜型断层的比例在中高纬度区较大 ;对整个统计区域而言 ,受增压型潮汐应力促滑作用的发震断层数比例大于受减压型潮汐应力促滑作用的发震断层 ;对不同的纬度区域 ,不同的潮汐应力作用方式与之促滑的发震断层类型也有不同的分布特征。最后 ,本文将中国及邻区受到潮汐触发作用的地震按构造应力  相似文献   

2个二次触发型太阳耀斑的射电时间轮廓及其日冕磁结构     

谢瑞祥  郝龙飞  颜毅华  许春  刘玉英  施硕彪  李维华 《天文研究与技术》2006,3(3):247-257

利用国家天文台(北京和昆明)的射电频谱仪(频段为0.65~7.6 GHz)和相关的NoRH/17GHz射电以及TRACE/171 EUV和Yohkoh/SXT的观测资料,分析了2001/04/10和10/19的2个共生精细时间结构的稀有事件,这2个事件的射电爆发时间轮廓和观测特征相似,通过这2个事件的微波(17GHz)偏振观测资料的比较,发现这2个射电爆发均由包含多重(4极)磁结构的复杂活动区引起,特别指出这2个耀斑最后都导致了耀斑后相的分米波射电爆发(第二次触发耀斑),这可能是后环引起的射电爆发。它们都分别对应于双极磁位形,表明这两次触发耀斑是由相似的耀斑模型产生。2个分米波爆发可能是相似(homologous)耀斑的射电表现,可以推测这两次耀斑的驱动器可能皆是磁流浮现或对消(因为源区有新的单或双极出现或消失),而它们的触发器皆是由双极反向Y型位形(具有一个双极拱的单磁流系统)的磁重联,耀斑后环的演化是导致耀斑后相分米波射电爆发的必要条件。我们认为,这双带耀斑对应的宽带射电爆发辐射机制是回旋同步加速辐射过程,而耀斑后相的窄带分米波爆发的辐射机制是等离子体辐射过程。  相似文献