Circulation pattern and current variations with respect to tidal frequency in the sea near the head of Suruga Bay

Current measurements were conducted 10 m below the sea surface near the head of Suruga Bay intermittently from 1970 to 1978. The circulation pattern is usually counterclockwise; northward along the east coast (off Heda and at the mouth of Uchiura Inlet), westward along the north coast (off Fuji), and southwestward along the west coast (off Shimizu). The amplitudes of the four major tidal constituents of current variation, M₂, S₂, K₁ and O₁, are much larger than those expected from sea level variations along the coast. The amplitudes of the diurnal constituents of current variation are much larger than those of the semidiurnal constituents, while the amplitudes of the semidiurnal constituents of sea level variation are much larger than those of the diurnal constituents. The observed amplitude of the predominant diurnal constituents exhibit large seasonal changes and tend to increase with the development of the stratification of the upper part of the water in Suruga Bay. These facts strongly suggest that the observed current variations are mainly associated with internal tides in Suruga Bay.     

Current variation in the sea near the mouth of Suruga Bay

In order to investigate the circulation pattern and the characteristics of tidal currents in the sea near the mouth of Suruga Bay, current meausrements were conducted at two stations at near-surface levels during the warm months of the year (late May to early October). The mean currents at the eastern and western stations are inversely correlated with each other: when inflow occurs at the eastern station outflow occurs at the western one andvice versa. The circulation pattern, therefore, can be determined from the mean current at either station,e.g., inflow or outflow at the eastern station corresponds to counterclockwise and clockwise circulation, respectively. The predominant tidal constituents of the measured currents are diurnal while those of the sea level along the bay are semidiurnal. The amplitudes of the diurnal constituents of the current show clear long-term variations besides the semimonthly variation corresponding to the phase of the moon.Variation in the path of the Kuroshio off the bay mouth seems to influence not only the circulation pattern but also the tidal currents in the sea near the bay mouth. When the Kuroshio axis is to the north of Zenisu, a shoal off the eastern side of the bay, the circulation pattern is counterclockwise and the amplitude of the tidal current is small. On the other hand, when the Kuroshio is to the south ofZenisu, the circulation pattern is weakly clockwise or stagnant and the amplitude of the tidal current is large.     

大亚湾海域夏、冬季的潮汐特征及余水位与风的相关性初步探讨

大亚湾及其邻近海域冬、夏季各14个临时水位观测点1个月的实测潮位资料显示:各站的水位曲线均呈现明显的"双峰"现象,且湾顶比湾口更为明显.本文采用了调和分析方法,给出M2、S2、K1、O1四个主要分潮及M4、M6、2MS6三个浅水分潮的振幅和迟角同潮图,分析大亚湾的主要潮汐特征,探讨了浅水分潮对双峰结构的贡献,并采用交叉...     

海岸围垦工程对三门湾内潮汐振幅的影响与研究

近年来随着三门湾内围垦工程规模的不断扩大,三门湾的岸线及水深地形发生了显著变化,有必要重新评估三门湾内的潮汐振幅特征。本研究基于ADCIRC二维潮汐模型,开展了三门湾围垦工程实施前后潮汐振幅变化规律的研究。结果表明:三门湾内以半日潮为主,湾口和湾顶处振幅相差较大。单纯考虑围垦工程引起的岸线变化时,半日潮振幅受到的影响较为明显,振幅以减小为主,M2分潮减小幅度为0. 08～0. 10 m。采用经验公式预测了围垦工程造成的最终回淤量,围垦工程附近平均淤积为1. 5～2. 5 m,深水区附近淤积更加严重。当考虑了回淤导致的地形变化后,围垦工程区附近的潮汐振幅会有显著的减小,半日分潮减小幅度要远大于全日分潮,在围垦区域前沿,M2分潮振幅减小幅度较为明显,然后向外侧逐步减小。与单纯岸线变化相比,水深地形改变导致的潮汐振幅变化幅度要远大于前者。     

杭州湾潮汐特征时空变化及原因分析

杭州湾是世界著名的强潮河口湾,一直是研究的热点。基于杭州湾口内外实测潮汐资料,对杭州湾潮汐特征及时空变化进行了系统分析,包括高潮位、低潮位、平均潮位、潮差、涨潮历时以及天文潮变化,同时分析了20世纪80年代以来潮汐特征变化的原因。结果表明:最近50年来,杭州湾年平均高潮位和海平面抬高,潮差增大;澉浦年平均低潮位抬高,涨潮历时缩短,浅海分潮增大;钱塘江河口治江缩窄是造成杭州湾潮汐变化的主要因素;浙江和邻近海域的涉海工程可能是造成浙江沿海海平面上升的主要原因之一。     

Numerical experiments of internal tides in Suruga Bay

Numerical experiments were performed to explain the observed results of the internal tides in Uchiura Bay. The experiments for the generation of the internal tides in Suruga Bay indicate that the internal tides, generated at the slopes in the bay, are not as large an amplitude as those observed in Uchiura Bay. However, when the semidiurnal internal tides incident through the mouth of Suruga Bay are considered, they are amplified. The amplitude at the head of Uchiura Bay is 6–12 times larger than that at the mouth of Suruga Bay under the summer density structure. Under the fall density structure, the amplitude ratio is approximately 4–6. The amplification of the semidiurnal internal tides in Uchiura Bay is considered to be due to resonance of the longitudinal internal seiche of Uchiura Bay. On the other hand, the calculated diurnal internal tides are not as large as those observed. Therefore, the diurnal internal tides are thought to already have these large amplitudes at the mouth of Suruga Bay. Therefore, from the observations and numerical experiments, it is concluded that the internal tides observed in Uchiura Bay are mostly the internal tides originating from the outer region of Suruga Bay, and the semidiurnal tides are the internal seiche which is resonantly amplified.     

基于FVCOM的厦门湾及其周边海域三维潮流数值模拟

基于非结构三角形网格、干-湿判别技术和有限体积法的FVCOM（finite volume coastal oceanmodel）海洋数值模式,建立了厦门湾及其周边海域高分辨率（30 m）的三维潮汐、潮流数值模型.模拟结果同该海域2个验潮站和4个连续海流站的观测资料符合良好,较好地反映了厦门湾及其周边海域潮汐、潮流运动的变化状况和分布特征,并给出了M2、S2、K1、O1共4个主要分潮的同潮图、表层潮流椭圆、最大可能潮流流速及表、底层潮余流分布.厦门湾及其周边海域属正规半日潮类型,4个分潮的最大潮汐振幅分别为200、65、36、29 cm,厦门湾内外迟角差分别为20°、25°、18°、10°;镇海角至围头角连线东南侧湾口区为逆时针旋转的驻波,西北侧湾内为前进潮波.湾内潮流属正规半日潮流,湾口区潮流以逆时针方向的旋转流运动为主,湾内各水道为往复潮流,椭圆长轴与水道走向一致,4个分潮流表层最大流速分别为201、51、34、25 cm/s;九龙江口区3条港道内的流速以南港最大;表层余流大于底层余流,二者水平分布形态基本一致,都为北进南出.     

基于船载ADCP观测对半封闭海湾湾口断面潮流及余流的分析（英文）

基于对罗源湾可门水道的25小时连续走航ADCP观测,本文成功构建了沿走航断面共12个站位的连续海流时间序列,并对这些站位的潮流、余流以及潮通量等进行了分析。结果表明可门水道内的潮流为正规半日潮流,驻波性质明显,涨潮首先出现在水道中下层而退潮则首先发生在水道上层。水道内潮流为往复流,水道南部M2分潮流流速较大,并且其倾角自北向南逐渐增加。此外,水道两端的浅水区域内浅水分潮M4振幅较显著。可门水道内余流呈现出两层结构,20m以浅余流沿东北向流出海湾,并且出流的核心位置偏南,而20m以深的余流沿西南向流入湾内,入流的流核位于偏北的近底层区域。对潮通量的积分计算表明通过可门水道进入罗源湾的潮通量约为4.81×10^8m^3。     

Fortnightly shifts of intrusion depth of oceanic water into Ise Bay

To clarify the time change in water exchanges between Ise Bay and the adjacent ocean, repeated hydrographic observations were conducted along the longitudinal section in Ise Bay. The results show that the mixing condition at the bay mouth (Irago Strait) changed fortnightly in summer. During the spring tides, the strait water below the pycnocline was well-mixed and nearly homogeneous. By contrast, it was weakly stratified during the neap tide. There is a strong negative correlation between the tidal range and the density difference between the upper and lower layers at the strait. In summer, the intrusion depth of oceanic water into the bay and consequent hydrographic conditions inside the bay changed frequently according to the tidal strength. During the spring tides a prominent bottom front was created at the bay mouth, indicating that the strait water, which is a mixture of oceanic and bay waters, intruded through the middle layer. On the other hand, during the neaps, cold and saline oceanic water intruded through the bottom layer into the bay. The intrusion depth is significantly correlated with the tidal range. It is considered that the wellmixed strait water, which has a density equivalent to the middle layer inside the bay, is lighter than the bottom bay water and thus intrudes through the middle layer during the spring tides, while insufficient mixing makes the bottom water at the strait heavier than the bay water, leading to the bottom intrusion during the neap tides.     

基于FVCOM 的辽东湾水动力特性数值模拟

辽东湾属于半封闭性海湾, 水动力过程具有一定的代表性。本文基于无结构化三角形网格的有限体积海岸海洋模型FVCOM（Finite-Volume Coastal Ocean Model）, 构建了辽东湾及其邻近海域的三维水动力数值模型, 并利用实测数据对6 个潮位验潮站、4 个潮流验潮站的大小潮时刻的潮位、流速、流向进行了对比验证, 该模型能够准确地模拟辽东湾的潮汐、潮流等水动力场情况, 可进一步为研究辽东湾温盐、泥沙、水质、污染物扩散等提供研究基础。     

Sea-level fluctuations in a coastal lagoon

Sea-level observations made during December, 1979, at six stations in Great South Bay (which is a coastal lagoon on the south shore of Long Island, New York) reveal that there were significant subtidal fluctuations in addition to the tidal oscillations. Harmonic analysis of the tidal oscillations of sea level indicates that M₂ is the dominant tidal constituent. The M₂ amplitude, however, suffered a more than 50% reduction in the interior of the Bay due largely to the narrow inlet. The subtidal sea level fluctuations within the Bay were forced primarily by the low-frequency fluctuations of the adjacent shelf water. The active subtidal exchange induced by this Bay-shelf coupling appeared to have suffered only minor attenuation within the Bay. As a consequence, the variance associated with subtidal sea level fluctuations was greater than that associated with the tidal oscillations over most of Great South Bay.     

Sea level fluctuations in central California at subtidal to decadal and longer time scales with implications for San Francisco Bay, California

Sea level elevations from near the mouth of San Francisco Bay are used to describe the low-frequency variability of forcing of the coastal ocean on the Bay at a variety of temporal scales. About 90% of subtidal fluctuations in sea level in San Francisco Bay are driven by the sea level variations in the coastal ocean that propagate into the Bay at the estuary mouth. We use the 100-year sea level record available at San Francisco to document a 1.9 mm/yr mean sea level rise, and to determine fluctuations related to El Nino-Southern Oscillation (ENSO) and other climatic events. At time scales greater than 1 year, ENSO dominates the sea level signal and can result in fluctuations in sea level of 10–15 cm. Alongshore wind stress data from central California are also analyzed to determine the impact of changes in coastal elevation at the mouth of San Francisco Bay within the synoptic wind band of 2–30 days. At least 40% of the subtidal fluctuations in sea level of the Bay are tied to the large-scale regional wind field affecting sea level variations in the coastal ocean, with little local, direct wind forcing of the Bay itself. The majority of the subtidal sea level fluctuations within the Bay that are not related to the coastal ocean sea level signal are forced by an east–west sea level gradient resulting from tidally induced variations in sea level at specific beat frequencies that are enhanced in the northern reach of the Bay. River discharge into the Bay through the Sacramento and San Joaquin River Delta also contributes to the east–west gradient, but to a lesser degree.     

Evidence for predominance of internal tidal currents in Sagami and Suruga bays

Tidal currents observed in a surface layer overlying deep water in Sagami and Suruga Bays frequently have large amplitude in summer and fall. Numerical experiments show that the current amplitude due to the surface tides is below 1.0 cm sec^–1 for the semidiurnal and diurnal constituents in the inner region of the two bays. The observed current amplitudes are larger than the calculated ones due to the surface tides. Therefore, the observed tidal currents are indicated to be due mainly to the internal tides. In addition, the semidiurnal currents dominate the diurnal currents in Sagami Bay, while the opposite occurs in Suruga Bay. These results suggest that the prevailing periods of the internal tides differ between the two bays,i.e., the internal tide has a semidiurnal period in Sagami Bay and a diurnal period in Suruga Bay.     

Tidal oscillations in the Baltic Sea

Long-term hourly data from 35 tide gauge stations, including 15 stations in the Gulf of Finland, were used to examine tidal sea level oscillations of the Baltic Sea. High-resolution spectral analysis revealed the well-defined fine structure of tidal peaks with diurnal peaks at most stations being higher than semidiurnal. At some stations (e.g., Narva, Daugava, and Wladyslawowo), high frequency radiational tidal peaks with periods multiple of the solar day (3, 4, 5, 6, and 8 cpd) were detected; the respective oscillations are supposed to be caused by seabreeze winds. Harmonic analysis of tides for individual yearly sea level series followed by vector averaging over the entire observational period was used to estimate the amplitudes and phases of 16 tidal constituents. The maximum tidal oscillations of 17–19 cm were found to be observed in the Gulf of Finland and, first of all, in Neva Bay (in the head of the gulf). Diurnal or mixed diurnal tides are predominant in almost the entire Baltic Sea. The comparison of the observed tides with those theoretically computed showed that the existing numerical models of the main tidal harmonics generally quite accurately reproduce the structure of the tides in the Baltic Sea except for some regions of the Gulf of Bothnia.     

基于FVCOM的廉州湾及周边海域三维潮汐潮流数值模拟(英文)

基于采用不规则三角网格和有限体积方法的FVCOM模式,建立廉州湾三维潮流数值模型来重现廉州湾及周边海域的潮位和潮流变化状况。根据模拟结果计算得到了较以往更为精细的廉州湾及周边海域K1、O1和M2分潮的同潮图,并计算了由此三个分潮引起的潮汐不对称的变化情况。K1和O1分潮在廉州湾外主要以驻波的形式存在,进入廉州湾后转化为前进波;M2分潮在廉州湾外主要以前进波的形式存在,进入廉州湾后前进波特征更为明显。K1和O1分潮流在廉州湾外以旋转流为主,在廉州湾内以往复流为主;M2分潮流在整个研究海域以往复流为主。由潮余流场的分布特点可以看出自南向北由外海进入廉州湾的潮余流,在冠头岭处分为两支,一支逆时针转向西,另一支被冠头岭阻挡在其南侧形成顺时针封闭环流。在廉州湾内部同时存在两个环流系统,湾顶的气旋式环流和口门处的反气旋式环流。     

Difference in the prevailing periods of internal tides between Sagami and Suruga Bays: Numerical experiments

Current measurements in the surface layer in Sagami and Suruga Bays showed existence of significant tidal currents which are considered to be mainly due to internal tides (Inaba, 1982; Ohwaki,ea al., 1991). In addition, the prevailing period of the tidal currents is semidiurnal in Sagami Bay, but diurnal in Suruga Bay. To explain this difference in the prevailing, periods, numerical experiments were carried out using a two layer model. The internal tides are generated on the Izu Ridge outside the two bays. The semidiurnal internal tide propagates into Sagami Bay having characteristics of an internal inertia-gravity wave, while it propagates into Suruga Bay having characteristics of either an internal inertia-gravity wave or an internal Kelvin wave. The diurnal internal tide behaves only as an internal Kelvin wave, because the diurnal period is longer than the inertia period. Thus, the diurnal internal tide generated on the Izu Ridge can be propagated into Suruga Bay, while it cannot propagate into the inner region of Sagami Bay, though it is trapped around Oshima Island, which is located at the mouth of Sagami Bay. The difference in the propagation characteristics between the semidiurnal and diurnal internal tides can give a mechanism to explain the difference in the prevailing periods of the internal tides between Sagami and Suruga Bays.     

基于FVCOM的廉州湾及周边海域三维潮汐潮流数值模拟

基于采用不规则三角网格和有限体积方法的FVCOM模式,建立廉州湾三维潮流数值模型来重现廉州湾及周边海域的潮位和潮流变化状况。根据模拟结果计算得到了较以往更为精细的廉州湾及周边海域K₁、O₁和M₂分潮的同潮图,并计算了由此3个分潮引起的潮汐不对称的变化情况。K₁和O₁分潮在廉州湾外主要以驻波的形式存在,进入廉州湾后转化为前进波;M₂分潮在廉州湾外主要以前进波的形式存在,进入廉州湾后前进波特征更为明显。K₁和O₁分潮流在廉州湾外以旋转流为主,在廉州湾内以往复流为主;M₂分潮流在整个研究海域以往复流为主。由潮余流场的分布特点可以看出自南向北由外海进入廉州湾的潮余流,在冠头岭处分为两支,一支逆时针转向西,另一支被冠头岭阻挡在其南侧形成顺时针封闭环流。在廉州湾内部同时存在2个环流系统,湾顶的气旋式环流和口门处的反气旋式环流。     

胶州湾的潮汐与潮流

胶州湾是我国沿海的一个重要港湾,长期以来对其进行了较多的调查研究工作。大港验潮站自1926年起开始观测(1936-1946年曾中断),目前已积累了44年的长期水位资料。山角底验潮站自1967年开始观测,也积累了16年的水位资料。我们还系统地搜集了我所1958-1959年在薛家岛、东洋嘴、团岛、麦岛、大公岛分别进行的四个月、两个月及半个月的观测资料,以及山东海洋学院1975年在红岛船厂(阴岛)、黄岛客运码头分别进行的三个月及两个月的水位观测资料和团岛湾、后岔湾、大石头等地的潮汐调和常数。此外,我们还搜集了胶州湾及其附近海区共二十三个测站的海流连续观测资料,其中十九个站的资料是由我所在1957-1959年观测的,三个站是1982年“全国海岸带调查”中测得的,另一个站是华东水利学院提供的资料。这些测站,除六个站为一昼夜连续观测外,其余十七个站均为二昼夜以上连续观测(有一个站为十五昼夜连续观测)。观测站位见图1。 我们把搜集到的这些潮汐、潮流资料进行了调和分析,得到了各主要分潮的调和常数及潮汐、潮流特征值。本文以此为基础,结合实测资料,分析了胶州湾潮汐、潮流的基本特征。     

东山湾潮流动力特征研究

东山湾是福建重要的天然良港．根据2008年8月的3个潮次11个测站实测潮流资料结合历史调查资料分析东山湾的潮流性质、运动形式、涨落潮流特性、余流等特征．结果表明,东山湾主要属于往复式的规则半日潮流,潮流作用较强,其口门处和湾内水道上的实测最大流速一般大于100cm／s．持续时间较长的风对东山湾的余流较大的影响,大潮期间湾内存在明显的反时针的水平余环流系统．     

伶仃洋洪季潮波传播变形及不对称性规律分析

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