Water exchange between Tokyo Bay and the Pacific Ocean during winter

Variability in water-exchange time between Tokyo Bay and the Pacific Ocean during winter is investigated based on the results of intensive field observation from November 2000 to March 2001. Water-exchange time between Tokyo Bay and the Pacific Ocean during winter mainly depends on the strength of northerly monsoon, being about 16 days under the weak monsoon and about 12 days under the strong monsoon. Moreover, it becomes longer by about 1 day in spring tide and shorter in neap tide due to the coupling effect of estuarine circulation and vertical mixing. Water-exchange time also varies depending on the open-ocean condition. When the warm water mass approaches from the Pacific Ocean to the mouth of Tokyo Bay through the eastern channel of Sagami Bay, which connects Tokyo Bay and the Pacific Ocean, water-exchange time becomes longer by about 2 days because the warm water mass is blocked in the surface layer at the bay mouth. On the other hand, when the warm water mass approaches to the mouth of Tokyo Bay through the western channel of Sagami Bay, water-exchange time becomes shorter by about 1 day because the warm water mass intrudes into the middle or lower layers of Tokyo Bay. Such different behavior of warm water mass at the mouth of Tokyo Bay is due to the difference in density of approaching warm water masses, that is, the density of the warm water mass through the eastern channel is smaller than that of the warm water mass through the western channel of Sagami Bay.Responsible Editors: Yens Kappenberg     

A parameterization of the wavelength of tidal dunes

The idealized model of Besio et al. (On the formation of sand waves and sand banks. Journal of Fluid Mechanics 2006; 557: 1–17) is used to predict the wavelength of tidal dunes (sand waves) generated by tidal currents in estuaries and shallow seas. The predictions are then analysed and a formula is proposed to estimate the wavelength of tidal dunes as a function of the parameters of the problem. The wavelength of the dunes is found to increase when the water depth is increased and/or the strength of the tidal current is decreased. On the other hand, the size of the bottom material (if medium sand is considered) and the tidal ellipticity are found to have a relatively small influence on the length of the bottom forms. The formula proposed provides results which are consistent with field observations of different authors. Copyright © 2011 John Wiley & Sons, Ltd.     

曹妃甸填海工程阻断浅滩潮道初期老龙沟深槽的地形变化

通过研究1992、1997、2006年的测深资料,对比分析了横切老龙沟深槽口门处的地形横剖面和大致沿老龙沟深槽轴线的地形纵剖面,可知在此期间深槽内的水深有变浅和淤积的趋势。总体看来,老龙沟深槽的淤积厚度在0.61~4.8 m之间,并且老龙沟深槽轴线也有自东向西迁移的趋势。自2004年曹妃甸填海工程的通岛公路阻断浅滩潮道后,使老龙沟深槽内的潮流流量和流速减小,是引起老龙沟深槽内的水深变浅和淤积的主要原因。淤积可能主要发生在通岛公路阻断浅滩潮道后的初期即2004-2006年期间。该研究结果也证实了我们阻断浅滩潮道会引起老龙沟深槽淤积的推断。     

条子泥一期工程对条子泥发育影响及工程防护措施

通过历史和现场观测资料并结合遥感卫片资料,对条子泥匡围一期工程两年多的建设过程中,由工程所引起对条子沙洲西大港、东大港、条鱼港等主要的潮沟,及相应的潮盆系统和二分水的剧烈变化进行了分析研究,总结了潮沟摆动治理经验。治理方法主要为丁坝群结合砼连锁块镇压排布防护技术等。     

河口往复流中潮流不对称与推移质输沙的关系

潮流不对称现象是近岸潮波运动的基本特征之一,为了研究潮流不对称对推移质泥沙长期净输运的作用机制,首先在往复流情况下对Bagnold推移质输沙率公式(1966)由于不包含起动流速所可能导致的误差进行理论分析,进而由统计学中的"偏度"的概念出发,推导了河口潮流不对称与推移质输沙之间的定量关系。研究认为,虽然Bagnold推移质输沙率公式不包含泥沙起动流速,但是只要泥沙起动流速和最大流速的比值在一定范围内,则在理论上公式的计算误差是可以接受的。由偏度结合Bagnold公式导出了潮流不对称与推移质输沙之间的关系,表明推移质泥沙的长期净输运不仅与余流有关,而且与不同分潮组合之间、余流与分潮之间的相互作用紧密相关。该关系还给出了一个由潮流调和常数估算河口推移质输沙的简便方法。经对比,从潮流不对称出发估算推移质输沙与直接采用推移质输沙率公式结果一致。     

基于稀疏AR模型的潮流信号建模与预报

潮流信号处理与预报在很多方面具有非常重要的意义和价值。本文引入信号稀疏表示理论,构建一种稀疏AR模型,寻找各潮流数据间的历史关联性,并进行预报分析。首先由实测潮流信号进行常规AR建模,获得一组过完备稀疏基;其次随机从该过完备稀疏基抽取部分建立欠定方程组,利用稀疏优化算法获得最稀疏的AR系数;多次重复上一步,获得稀疏AR系数的平均以增强稀疏AR模型的稳定性;最后利用这些稀疏AR系数来重构或预测潮流信号。文章针对实测潮流信号,特别是存在多峰值有回流现象的潮流信号,进行了稀疏AR建模与预测的多次实验。实验结果与传统的潮流信号调和预报方法相对比,发现基于稀疏AR模型的潮流预报对于潮流存在多变的现象时,具有明显优越性,从回报结果来看,稀疏AR模型的潮流预报均方差明显小于传统潮流调和分析预报方法。     

Observations of resuspended diatoms in the turbid tidal edge

Observations of resuspended diatoms in the shallow waters (<60 cm) of the turbid tidal edge are described for single sites on two tidal flats–the Molenplaat in the Westerschelde estuary, and the Hond in the Ems-Dollard estuary, The Netherlands. High concentrations of chlorophyll-a (chl-a) were observed in the trailing edge of the ebbing tide in water depths of <20 cm, after which concentrations decreased markedly. Peak mean values were 19 μg chl-a l⁻¹ in 10 cm of water at the Molenplaat, and 45 μg chl-a l⁻¹ in 5 cm of water at the Hond. Similar trends were observed on the flooding tide, although peak values were far less pronounced (6 and 30 μg chl-a l⁻¹ respectively). Microscopic examination of the diatom community within the turbid tidal edge at the Molenplaat revealed that peaks in biomass were caused by suspended benthic diatoms, as well as the large centric diatom Coscinodiscus sp., particularly on the ebb tide. Planktonic diatoms other than Coscinodiscus sp. were more randomly distributed and did not appear to follow any particular trend. It would seem that as the tide recedes, resuspended benthic diatoms and large Coscinodiscus sp. cells become concentrated in the shallow water. However, the virtual absence of Coscinodiscus sp. from the leading edge of the flooding tide suggests that most of the resuspended cells do not settle to the seabed, but are washed away into the channels. The small peak of benthic diatoms at the leading edge of the flood tide is most likely resuspended locally from the sediment, along with large numbers of diatom frustules.     

一套有效简易验潮站建设方案的设计

简易验潮站具有投资少、见效快的优点,是长期验潮站的一种有益补充。作者对厦门地区简易验潮站建设与应用情况进行了系统总结,提出了一种简易验潮站的建设方案。该方案经实践检验证明可以解决在一定环境条件下简易验潮站长期、连续、准确验潮的问题,从而提高社会效益和经济效益,具有良好的推广示范价值。     

Coastal Upwelling Activity on the Pacific Shelf of the Baja California Peninsula

High primary productivity on the Pacific coast of the Baja California Peninsula is usually related to coastal upwelling activity that injects nutrients into the euphotic zone in response to prevailing longshore winds (from the northwest to north). The upwelling process has maximum intensity from April to June, with the coastal upwelling index varying from 50 to 300 m³/s per 100 m of coastline. Along the entire coast of the peninsula, the upwelling intensity changes in accordance with local wind conditions and bottom topography. Spatial variability can also be modulated by the influence of mesoscale meanders of the California Current. We have identified the seasonal and synoptic variability of upwelling signatures on the Baja California shelf, using averaged monthly and weekly sea surface temperature (SST) distributions obtained from remote sensing imagery from the Advanced Very High Resolution Radiometer in the period from 1996 to 2001. Analysis of SST distribution and direct experimental data on temperature and nutrient concentration shows that the areas with the coldest SST anomalies were closely related to the bottom slope, shelf width, and coastline orientation relating to wind direction. We also assume that the nutrient transport into the coastal lagoons may be forced by the coupling of coastal upwelling and tidal pumping of surface waters into the lagoon system. This revised version was published online in August 2006 with corrections to the Cover Date.     

天津港水域围垦条件下的水动力变化分析

本研究旨在讨论天津滨海新区的围垦对其附近水域水动力和悬沙输运所造成的影响,并进行定量评估。在天津港南部、北部海域分别选取4个站位进行了全潮水文观测,获取了流速剖面、悬沙浓度剖面数据,并据此计算了底切应力、潮不对称性以及余流。结果表明,底部悬沙浓度与流速、底切应力存在相位一致性,绝大部分站位的沉积物都呈现向岸净输运的趋势,悬沙通量分解显示潮汐捕捉项是该区域悬沙输运的主要贡献项;围垦愈增的2009～2015年,天津港北部潮不对称性增强,向陆的单宽悬沙输运率由20.15 g/(m·s)变至24.92 g/(m·s),而南部海域潮不对称性减弱,向陆的单宽悬沙输运率从37.75 g/(m·s)减小至6.37 g/(m·s)。综上,持续地围垦可能导致天津港附近海域的水动力条件改变,推测北部潮滩淤涨可能加快,而南部淤涨速率减小。