scholarly journals STUDIES ON THE CORRELATION OF TIDAL ELEVATION CHANGES ALONG THE WESTERN COASTLINE OF TAIWAN

1986 ◽  
Vol 1 (20) ◽  
pp. 23 ◽  
Author(s):  
H.H. Hwung ◽  
C.L. Tsai ◽  
C.C. Wu
Keyword(s):  
Energy Density ◽  
Harmonic Analysis ◽  
Water Level ◽  
High Water ◽  
Maximum Energy ◽  
Phase Lag ◽  
Tidal Elevation ◽  
Elevation Changes ◽  
Tidal Constituents ◽  
Phase Angles

In order to understand the characteristics of tidal elevation changes along the western coastline of Taiwan, the authors collected the tidal records at the same duration from eleven stations and made an elaborate analysis in this paper. First step, the main tidal constituents were picked out from spectrum analysis, and the amplitudes and phase angles of these tidal constituents would be obtained by harmonic analysis. Then the variations of amplitude and phase lag of the main constituents and the variations of mean high water level and mean low water level along the coastline would be presented in the figures respectively. Finally, based on the results of harmonic analysis, the energy density of tide for every station could be calculated separately, and the location of the maximum energy density would be determined by cubic spline method.

scholarly journals Seasonal variation of the principal tidal constituents in the Bohai Sea

Ocean Science ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Daosheng Wang ◽  
Haidong Pan ◽  
Guangzhen Jin ◽  
Xianqing Lv
Keyword(s):  
Seasonal Variation ◽  
Harmonic Analysis ◽  
Sea Level ◽  
Seasonal Variations ◽  
Eddy Viscosity ◽  
Bohai Sea ◽  
Phase Lag ◽  
Vertical Eddy Viscosity ◽  
Tidal Constituents ◽  
Vertical Eddy

Abstract. The seasonal variation of tides plays a significant role in water level changes in coastal regions. In this study, seasonal variations of four principal tidal constituents, M2, S2, K1, and O1, in the Bohai Sea, China, were studied by applying an enhanced harmonic analysis method to two time series: 1-year sea level observations at a mooring station (named E2) located in the western Bohai Sea and 17-year sea level observations at Dalian. At E2, the M2 amplitude and phase lag have annual frequencies, with large values in summer and small values in winter, while the frequencies of S2 and K1 amplitudes are also nearly annual. In contrast, the O1 amplitude increases constantly from winter to autumn. The maxima of phase lags appear twice in 1 year for S2, K1, and O1, taking place near winter and summer. The seasonal variation trends estimated by the enhanced harmonic analysis at Dalian are different from those at E2, except for the M2 phase lag. The M2 and S2 amplitudes show semi-annual and annual cycles, respectively, which are relatively significant at Dalian. The results of numerical experiments indicate that the seasonality of vertical eddy viscosity induces seasonal variations of the principal tidal constituents at E2. However, the tested mechanisms, including seasonally varying stratification, vertical eddy viscosity, and mean sea level, do not adequately explain the observed seasonal variations of tidal constituents at Dalian.

scholarly journals HIGH AND LOW WATER PREDICTION AT LAGOS HARBOUR, NIGERIA

2017 ◽  
Vol 36 (3) ◽  
pp. 944-952
Author(s):  
OT Badejo ◽  
SO Akintoye
Keyword(s):  
Prediction Model ◽  
White Noise ◽  
Harmonic Analysis ◽  
Least Squares ◽  
Water Level ◽  
Observational Period ◽  
Tidal Constituent ◽  
Tidal Harmonic ◽  
Tidal Data ◽  
Tidal Constituents

In this work, 500 hourly water level tidal data were used to perform least squares tidal harmonic analysis. Eleven tidal constituents were used for the harmonic analysis. Astronomical arguments (v + u) and the nodal factor (f) were computed for each tidal constituent and at each observational period with a programme written in Matlab environment. The harmonic constants determined from the least squares tidal harmonic analysis were substituted into a tidal prediction model to predict hourly tidal data and tidal predictions at 5 minutes’ intervals. Series of high and low water heights from the tidal predictions made at 5 minutes’ intervals were determined and matched with their corresponding times. Autocorrelation at lags 1 to 30 for the residuals of the observed and predicted tidal data shows that there is no significant correlation in the range of the 30 lags. The series of residuals of the observed and predicted tidal data is therefore white noise.   http://dx.doi.org/10.4314/njt.v36i3.39

Tidal studies on Aldabra

1971 ◽  
Vol 260 (836) ◽  
pp. 93-121 ◽  
Keyword(s):  
Water Level ◽  
Time Lag ◽  
Spring Tide ◽  
High Water ◽  
Wire Mesh ◽  
Tidal Range ◽  
Masking Effect ◽  
Phase Lag ◽  
Central Pacific ◽  
Du Bois

The oceanic tide at Aldabra possesses a very large range for an atoll owing to the influence of the Mozambique Channel. The mean spring-tide range, expressed as 2 ( M 2 + S 2 ), is 2.74 m. This is much greater than the 0.5 m common to the majority of central Pacific atolls, and the 0.7 to 1.7 m for Indian Ocean atolls. Ten tide-recording stations were set up by members of the expedition. Foxboro—Yoxall tide-gauge records were obtained from most sites, though there are few accessible rock ledges near deep water suitable for the instrument, especially in the lagoon. Visual records were used extensively in a detailed study of the tidal system in Passe Houareau. Tidal predictions for Aldabra found in Admiralty Tide Tables possess marked lagoonal characteristics. They originate from ‘Grand Poste’, a site well within Grande Passe. It is recommended that records for Passe du Bois be taken as standard since they most closely represent the oceanic tide. Empirically derived tide-predicting graphs are presented for key stations around the atoll, using Kilindini as standard port. Reduction in tidal range is pronounced in the lagoon and is conspicuous even near the mouths of the major channels. Within Passe Houareau spring-tide amplitudes may be a mere 1.2 m only 500 m from the channel mouth where the oceanic range is 3.3 m. Time lag increases lagoonwards more rapidly at Passe Houareau than at either Passe du Bois or Grande Passe, and is greater at low water than at high because of the very shallow nature of the lagoon floor. The greatest recorded phase lag occurs at the head of Bras Cinq Cases, where high water is delayed by 4 1/4 h at major spring tides: at neaps the whole region is dry at high water. Harmonic analyses are presented for one oceanic and two lagoonal stations. Computer synthesis of neap tides in the lagoon demonstrates a monthly masking effect produced by prominent shallow water harmonics. This results in the lagoon being virtually tideless on the smallest neap tides. Strong higher harmonics are indicated by visual records for Ilot Marquoix at the eastern end of the lagoon. These are characterized by a plateau-like high water, where the level commonly remains stationary for over 3 h. Lagoon tide curves are markedly asymmetrical, and often show linear ebb profiles, indicating that the lagoon behaves as a simple water-filled basin in many areas. Drainage off lagoon platforms is slow, water level falling by only 3 to 5 cm h -1 . This results in the tide ebbing for to 10 h out of the 12 1/2 h cycle. Towards spring tides more water enters the lagoon through Passe Houareau than can drain away before the next tide. Water level gradually builds up until at major springs a foot of water covers the lagoon platform at low tide. Extreme low water coincides with neap tides. Because of this ponding effect significant differences in insolation are experienced by marine bottom communities. On oceanic platforms extreme low water coincides with spring tides and occurs at midday: in the lagoon, platforms are most exposed between 06h00 and 08h00 and are always covered at noon. The effects of solar insolation are therefore minimal throughout much of the Aldabra lagoon, but are at a maximum around the coast. Tidal currents were measured in each of the Passes. In the western channels maximum values of 1.5 m s -1 (3 knots) were recorded in Passe du Bois. In Passe Gionnet a peak ebb value of 3.7 m s -1 (7.2 knots) was attained at high springs, with 3 m s -1 (6 knots) sustained for over 2 h. Flow/ebb current reversals are rapid, and in Passe Gionnet accompanied by the development of standing waves. Many channels are floored with trains of reversing sand megaripples. Elsewhere scour is appreciable; a wire mesh shark cage on the floor of Passe du Bois being undercut by 25 cm in 2 weeks. Transitory megarippled sandbanks occur on the eastern flank of Passe Houareau, and bottom facies throughout the lagoon are sculptured by the strong tidal scour.

Lake and inland dunes as interconnected Systems: The story of Lake Tresssee and an adjacent dune field (Schleswig-Holstein, North Germany)

The Holocene ◽  
2020 ◽  
pp. 095968362098168
Author(s):  
Christian Stolz ◽  
Magdalena Suchora ◽  
Irena A Pidek ◽  
Alexander Fülling
Keyword(s):  
Water Level ◽  
Bronze Age ◽  
Environmental Changes ◽  
High Water ◽  
Alluvial Fan ◽  
Water Levels ◽  
Lake Area ◽  
Dune Field ◽  
The North ◽  
Sand Drift

The specific aim of the study was to investigate how four adjacent geomorphological systems – a lake, a dune field, a small alluvial fan and a slope system – responded to the same impacts. Lake Tresssee is a shallow lake in the North of Germany (Schleswig-Holstein). During the Holocene, the lake’s water surface declined drastically, predominately as a consequence of human impact. The adjacent inland dune field shows several traces of former sand drift events. Using 30 new radiocarbon ages and the results of 16 OSL samples, this study aims to create a new timeline tracing the interaction between lake and dunes, as well, as how both the lake and the dunes reacted to environmental changes. The water level of the lake is presumed to have peaked during the period before the Younger Dryas (YD; start at 10.73 ka BC). After the Boreal period (OSL age 8050 ± 690 BC) the level must have undergone fluctuations triggered by climatic events and the first human influences. The last demonstrable high water level was during the Late Bronze Age (1003–844 cal. BC). The first to the 9th century AD saw slightly shrinking water levels, and more significant ones thereafter. In the 19th century, the lake area was artificially reduced to a minimum by the human population. In the dunes, a total of seven different phases of sand drift were demonstrated for the last 13,000 years. It is one of the most precisely dated inland-dune chronologies of Central Europe. The small alluvial fan took shape mainly between the 13th and 17th centuries AD. After 1700 cal. BC (Middle Bronze Age), and again during the sixth and seventh centuries AD, we find enhanced slope activity with the formation of Holocene colluvia.

High field tunneling as a limiting factor of maximum energy density in dielectric energy storage capacitors

2008 ◽  
Vol 92 (14) ◽  
pp. 142909 ◽  
Author(s):  
Qin Chen ◽  
Yong Wang ◽  
Xin Zhou ◽  
Q. M. Zhang ◽  
Shihai Zhang
Keyword(s):  
Energy Storage ◽  
Energy Density ◽  
High Field ◽  
Maximum Energy ◽  
Limiting Factor

scholarly journals Proglacial river dataset from the Akuliarusiarsuup Kuua River northern tributary, Southwest Greenland, 2008–2010

2011 ◽  
Vol 4 (1) ◽  
pp. 71-97 ◽  
Author(s):  
A. K. Rennermalm ◽  
L. C. Smith ◽  
V. W. Chu ◽  
R. R. Forster ◽  
J. E. Box ◽  
...  
Keyword(s):  
Water Level ◽  
Statistical Tests ◽  
Ice Sheet ◽  
High Water ◽  
Stream Channels ◽  
Discharge Data ◽  
Lake Water Level ◽  
Considerable Uncertainty ◽  
Added Uncertainty ◽  
Southwest Greenland

Abstract. Pressing scientific questions concerning the Greenland ice sheet's climatic sensitivity, hydrology, and contributions to current and future sea level rise require hydrological datasets to resolve. While direct observations of ice sheet meltwater losses can be obtained in terrestrial rivers draining the ice sheet and from lake levels, few such datasets exist. We present a new dataset of meltwater river discharge for the vicinity of Kangerlussuaq, Southwest Greenland. The dataset contains measurements of river water level and discharge for three sites along the Akuliarusiarsuup Kuua (Watson) River's northern tributary, with 30 min temporal resolution between June 2008 and August 2010. Additional data of water temperature, air pressure, and lake water level and temperature are also provided. Discharge data were measured at sites with near-ideal properties for such data collection. Regardless, high water bedload and turbulent flow introduce considerable uncertainty. These were constrained and quantified using statistical techniques, which revealed that the greatest discharge data uncertainties are associated with streambed elevation change and measurements. Large portions of stream channels deepened according to statistical tests, but poor precision of streambed depth measurements also added uncertainty. Data will periodically be extended, and are available in Open Access at doi:10.1594/PANGAEA.762818.

scholarly journals NON-BREAKING AND BREAKING WAVE LOADS ON A COOLING WATER OUTFALL

1978 ◽  
Vol 1 (16) ◽  
pp. 148
Author(s):  
G.R. Mogridge ◽  
W.W. Jamieson
Keyword(s):  
Water Level ◽  
Cooling Water ◽  
High Water ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Scale Model ◽  
Breaking Wave ◽  
Wave Loads ◽  
Eastern Canada ◽  
Spilling Breakers

Cooling water from a power generating station in Eastern Canada is pumped to an outfall and distributed into the ocean through discharge ports in the sidewalls of a diffuser cap. The cap is essentially a shell-type structure consisting of a submerged circular cylinder 26.5 ft in diameter and 14 ft high. It is located in 25 ft of water at low water level and 54 ft at high water level. Horizontal forces, vertical forces and overturning moments exerted by waves on a 1:36 scale model of the diffuser cap were measured with and without cooling water discharging from the outfall. Tests were run with regular and irregular waves producing both non-breaking and breaking wave loads on the diffuser cap. The overturning moments measured on the diffuser cap were up to 150 percent greater than those on a solid submerged cylinder sealed to the seabed. Unlike sealed cylinders, all of the wave loads measured on the relatively open structure reached maximum values at approximately the same time. The largest wave loads were measured on the diffuser structure when it was subjected to spilling breakers at low water level. For a given wave height, the spilling breakers caused wave loads up to 100 percent greater than those due to non-breaking waves.

scholarly journals Distribution of coastal high water level during extreme events around the UK and Irish coasts

2021 ◽  
Author(s):  
Julia Rulent ◽  
Lucy M. Bricheno ◽  
Mattias J. A. Green ◽  
Ivan D. Haigh ◽  
Huw Lewis
Keyword(s):  
Water Level ◽  
Extreme Events ◽  
High Tide ◽  
High Water ◽  
Relative Contribution ◽  
High Flood ◽  
Environmental Prediction ◽  
The Uk ◽  
Total Water Level ◽  
Tidal Stage

Abstract. The interaction between waves, surges and astronomical tides can lead to high coastal total water level (TWL), which can in turn lead to coastal flooding. Here, a high resolution (1.5 km) simulation from a UK-focused regional coupled environmental prediction system is used to investigate the extreme events of winter 2013/4 around the UK and Irish coasts. The aim is to analyse the spatial distribution of coastal TWL and its components during this period by assessing 1- the relative contribution of different TWL components around the coast, 2- how extreme waves, surges and tide interacted and if they occurred simultaneously 3- if this has implications in defining the severity of coastal hazard conditions. The TWL components’ coastal distribution in winter 2013/4 was not constant in space, impacting differently over different regions. High (> 90th percentile) waves and surges occurred simultaneously at any tidal stage, including high tide (7.7 % of cases), but more often over the flood tide. During periods of high flood risk a hazard proxy, defined as the sum of the sea surface height and half the significant wave height, at least doubled from average over ¾ of the coast. These results have important implications for the risk management sector.

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