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1
Agnew, Duncan C. "Time and tide: pendulum clocks and gravity tides." History of Geo- and Space Sciences 11, no. 2 (September 16, 2020): 215–24. http://dx.doi.org/10.5194/hgss-11-215-2020.
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Abstract. Tidal fluctuations in gravity will affect the period of a pendulum and hence the timekeeping of any such clock that uses one. Since pendulum clocks were, until the 1940s, the best timekeepers available, there has been interest in seeing if tidal effects could be observed in the best performing examples of these clocks. The first such observation was in 1929, before gravity tides were measured with spring gravimeters; at the time of the second (1940–1943), such gravimeters were still being developed. Subsequent observations, having been made after pendulum clocks had ceased to be the best available timekeepers and after reliable gravimeter measurements of tides, have been more of an indication of clock quality than a contribution to our knowledge of tides. This paper describes the different measurements and revisits them in terms of our current knowledge of Earth tides. Doing so shows that clock-based systems, though noisier than spring gravimeters, were an early form of an absolute gravimeter that could indeed observe Earth tides.
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Link, Denise, and Lois Wessel. "Time and Tides." Journal for Nurse Practitioners 18, no. 4 (April 2022): 351–52. http://dx.doi.org/10.1016/j.nurpra.2022.02.021.
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Melchior, Paul. "Tides in our time." Nature 398, no. 6723 (March 1999): 119–20. http://dx.doi.org/10.1038/18153.
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Ray, Richard D., and David E. Cartwright. "Times of peak astronomical tides." Geophysical Journal International 168, no. 3 (March 2007): 999–1004. http://dx.doi.org/10.1111/j.1365-246x.2006.03293.x.
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Dawes, Kwame, and Jared Angira. "Tides of Time: Selected Poems." World Literature Today 71, no. 4 (1997): 851. http://dx.doi.org/10.2307/40153466.
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Zaron, Edward D., and Gary D. Egbert. "Time-Variable Refraction of the Internal Tide at the Hawaiian Ridge." Journal of Physical Oceanography 44, no. 2 (February 1, 2014): 538–57. http://dx.doi.org/10.1175/jpo-d-12-0238.1.
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Abstract The interaction of the dominant semidiurnal M2 internal tide with the large-scale subtidal flow is examined in an ocean model by propagating the tide through an ensemble of background fields in a domain centered on the Hawaiian Ridge. The background fields are taken from the Simple Ocean Data Assimilation (SODA) ocean analysis, at 2-month intervals from 1992 through 2001. Tides are computed with the Primitive Equation Z-coordinate Harmonic Analysis of Tides (PEZ-HAT) model by 14-day integrations using SODA initial conditions and M2 tidal forcing. Variability of the tide is found to occur primarily as the result of propagation through the nonstationary background fields, rather than via generation site variability. Generation of incoherent tidal variability is mapped and shown to occur mostly in association with waves generated at French Frigate Shoals scattering near the Musicians Seamounts to the north of the ridge. The phase-coherent internal tide loses energy at a domain-average rate of 2 mW m−2 by scattering into the nonstationary tide. Because of the interference of waves from multiple generation sites, variability of the internal tide is spatially inhomogeneous and values of the scattering rate 10 times larger occur in localized areas. It is estimated that 20% of the baroclinic tidal energy flux is lost by adiabatic scattering (refraction) within 250 km of the ridge, a value regarded as a lower bound because of the smoothed nature of the SODA fields used in this study.
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Gao, Guanghai, Junqiang Xia, Roger A. Falconer, and Yingying Wang. "Modelling Study of Transport Time Scales for a Hyper-Tidal Estuary." Water 12, no. 9 (August 30, 2020): 2434. http://dx.doi.org/10.3390/w12092434.
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This paper presents a study of two transport timescales (TTS), i.e., the residence time and exposure time, of a hyper-tidal estuary using a widely used numerical model. The numerical model was calibrated against field measured data for various tidal conditions. The model simulated current speeds and directions generally agreed well with the field data. The model was then further developed and applied to study the two transport timescales, namely the exposure time and residence time for the hyper-tidal Severn Estuary. The numerical model predictions showed that the inflow from the River Severn under high flow conditions reduced the residence and exposure times by 1.5 to 3.5% for different tidal ranges and tracer release times. For spring tide conditions, releasing a tracer at high water reduced the residence time and exposure time by 49.0% and 11.9%, respectively, compared to releasing the tracer at low water. For neap tide conditions, releasing at high water reduced the residence time and exposure time by 31.6% and 8.0%, respectively, compared to releasing the tracer at low water level. The return coefficient was found to be vary between 0.75 and 0.88 for the different tidal conditions, which indicates that the returning water effects for different tidal ranges and release times are all relatively high. For all flow and tide conditions, the exposure times were significantly greater than the residence times, which demonstrated that there was a high possibility for water and/or pollutants to re-enter the Severn Estuary after leaving it on an ebb tide. The fractions of water and/or pollutants re-entering the estuary for spring and neap tide conditions were found to be very high, giving 0.75–0.81 for neap tides, and 0.79–0.88 for spring tides. For both the spring and neap tides, the residence and exposure times were lower for high water level release. Spring tide conditions gave significantly lower residence and exposure times. The spatial distribution of exposure and residence times showed that the flow from the River Severn only had a local effect on the upstream part of the estuary, for both the residence and exposure time.
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Hart-Davis, Michael G., Denise Dettmering, Roman Sulzbach, Maik Thomas, Christian Schwatke, and Florian Seitz. "Regional Evaluation of Minor Tidal Constituents for Improved Estimation of Ocean Tides." Remote Sensing 13, no. 16 (August 21, 2021): 3310. http://dx.doi.org/10.3390/rs13163310.
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Satellite altimetry observations have provided a significant contribution to the understanding of global sea surface processes, particularly allowing for advances in the accuracy of ocean tide estimations. Currently, almost three decades of satellite altimetry are available which can be used to improve the understanding of ocean tides by allowing for the estimation of an increased number of minor tidal constituents. As ocean tide models continue to improve, especially in the coastal region, these minor tides become increasingly important. Generally, admittance theory is used by most global ocean tide models to infer several minor tides from the major tides when creating the tidal correction for satellite altimetry. In this paper, regional studies are conducted to compare the use of admittance theory to direct estimations of minor tides from the EOT20 model to identify which minor tides should be directly estimated and which should be inferred. The results of these two approaches are compared to two global tide models (TiME and FES2014) and in situ tide gauge observations. The analysis showed that of the eight tidal constituents studied, half should be inferred (2N2, ϵ2, MSF and T2), while the remaining four tides (J1, L2, μ2 and ν2) should be directly estimated to optimise the ocean tidal correction. Furthermore, for certain minor tides, the other two tide models produced better results than the EOT model, suggesting that improvements can be made to the tidal correction made by EOT when incorporating tides from the two other tide models. Following on from this, a new approach of merging tidal constituents from different tide models to produce the ocean tidal correction for satellite altimetry that benefits from the strengths of the respective models is presented. This analysis showed that the tidal correction created based on the recommendations of the tide gauge analysis provided the highest reduction of sea-level variance. Additionally, the combination of the EOT20 model with the minor tides of the TiME and FES2014 model did not significantly increase the sea-level variance. As several additional minor tidal constituents are available from the TiME model, this opens the door for further investigations into including these minor tides and optimising the tidal correction for improved studies of the sea surface from satellite altimetry and in other applications, such as gravity field modelling.
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Ferraz-Mello, S. "On Tides and Exoplanets." Proceedings of the International Astronomical Union 15, S364 (October 2021): 20–30. http://dx.doi.org/10.1017/s1743921322000059.
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AbstractThis paper reviews the basic equations used in the study of the tidal variations of the rotational and orbital elements of a system formed by one star and one close-in planet as given by the creep tide theory and Darwin’s constant time lag (CTL) theory. At the end, it reviews and discusses the determinations of the relaxation factors (and time lags) in the case of host stars and hot Jupiters based on actual observations of orbital decay, stellar rotation and age, etc. It also includes a recollection of the basic facts concerning the variations of the rotation of host stars due to the leakage of angular momentum associated with stellar winds.
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Allbrooke, Jill. "The Life and Times of Time and Tide." Serials: The Journal for the Serials Community 8, no. 1 (March 1, 1995): 72–75. http://dx.doi.org/10.1629/0872.
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Hocking, W. K., and A. Hocking. "Temperature tides determined with meteor radar." Annales Geophysicae 20, no. 9 (September 30, 2002): 1447–67. http://dx.doi.org/10.5194/angeo-20-1447-2002.
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Abstract. A new analysis method for producing tidal temperature parameters using meteor radar measurements is presented, and is demonstrated with data from one polar and two mid-latitude sites. The technique further develops the temperature algorithm originally introduced by Hocking (1999). That earlier method was used to produce temperature measurements over time scales of days and months, but required an empirical model for the mean temperature gradient in the mesopause region. However, when tides are present, this temperature gradient is modulated by the presence of the tides, complicating extraction of diurnal variations. Nevertheless, if the vertical wavelengths of the tides are known from wind measurements, the effects of the gradient variations can be compensated for, permitting determination of temperature tidal amplitudes and phases by meteor techniques. The basic theory is described, and results from meteor radars at Resolute Bay (Canada), London (Canada) and Albuquerque (New Mexico, USA) are shown. Our results are compared with other lidar data, computer models, fundamental tidal theory and rocket data. Phase measurements at two mid-latitude sites (Albuquerque, New Mexico, and London, Canada) show times of maximum for the diurnal temperature tide to change modestly throughout most of the year, varying generally between 0 h and 6 h, with an excursion to 12 h in June at London. The semidiurnal tide shows a larger annual variation in time of maximum, being at 2–4 h in the winter months but increasing to 9 h during the late summer and early fall. We also find that, at least at mid-latitudes, the phase of the temperature tide matches closely the phase of the meridional tide, and theoretical justification for this statement is given. We also demonstrate that this is true using the Global Scale Wave Model (Hagan et al., 1999). Median values for the temperature amplitudes for each site are in the range 5 to 6 Kelvin. Results from a more northern site (Resolute Bay) show less consistency between the wind tides and the temperature tides, supporting suggestions that the temperature tides may be zonally symmetric at these high latitudes (e.g. Walterscheid and Sivjee, 2001).Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides) – Radio science (signal processing)
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Li, Qing, Weizhi Lu, Hui Chen, Yiqi Luo, and Guanghui Lin. "Differential Responses of Net Ecosystem Exchange of Carbon Dioxide to Light and Temperature between Spring and Neap Tides in Subtropical Mangrove Forests." Scientific World Journal 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/943697.
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The eddy flux data with field records of tidal water inundation depths of the year 2010 from two mangroves forests in southern China were analyzed to investigate the tidal effect on mangrove carbon cycle. We compared the net ecosystem exchange (NEE) and its responses to light and temperature, respectively, between spring tide and neap tide inundation periods. For the most time of the year 2010, higher daytime NEE values were found during spring tides than during neap tides at both study sites. Regression analysis of daytime NEE to photosynthetically active radiation (PAR) using the Landsberg model showed increased sensitivity of NEE to PAR with higher maximum photosynthetic rate during spring tides than neap tides. In contrast, the light compensation points acquired from the regression function of the Landsberg model were smaller during spring tides than neap tides in most months. The dependence of nighttime NEE on soil temperature was lower under spring tide than under neap tides. All these results above indicated that ecosystem carbon uptake rates of mangrove forests were strengthened, while ecosystem respirations were inhibited during spring tides in comparison with those during neap tides, which needs to be considered in modeling mangrove ecosystem carbon cycle under future sea level rise scenarios.
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Johnson, Eric S., and Michael L. Van Woert. "Tidal currents of the Ross Sea and their time stability." Antarctic Science 18, no. 1 (March 2006): 141–54. http://dx.doi.org/10.1017/s0954102006000137.
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Current measurements obtained from a sparse array of moorings on the Ross Continental Shelf during the 1980 and 90s are analysed for their tidal constituents. Diurnal (K1 and O1) tides are about five times stronger than semi-diurnal tides, and are strongest near the shelf break in agreement with recent model results. At some energetic locations the diurnal tides are significantly weaker at depth, presumably due to bottom friction. Complex demodulation analysis shows that at some locations the tidal response varies significantly in time. This time variability rises markedly above the noise floor expected from the spectral continuum between tidal bands, and does not scale with tidal bandwidth as would be expected of broadband noise. Further its magnitude is generally proportional to the associated tidal constituent, indicating that it is truly a varying tidal response. Space scales of this tidal instability were not resolved but are less than 150 km, while time scales appear mostly seasonal to interannual. The rms magnitude of the unstable response can be 1/3 of a given component’s mean magnitude, placing substantial limits on the ability of prognostic or even data assimilative models to accurately predict these tides for any specific time period.
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Zetler, B. D., and R. E. Flick. "Predicted Extreme High Tides for Mixed-Tide Regimes." Journal of Physical Oceanography 15, no. 3 (March 1985): 357–59. http://dx.doi.org/10.1175/1520-0485(1985)015<0357:pehtfm>2.0.co;2.
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Dunn, Gordon E. "HURRICANES AND HURRICANE TIDES." Coastal Engineering Proceedings 1, no. 6 (January 29, 2011): 2. http://dx.doi.org/10.9753/icce.v6.2.
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Most of the maximum tides of record between Cape Hatteras, N.C., and Brownsville, Tex., have been produced by tropical cyclones, or, as they are generally known in the United States, hurricanes. Some of the highest tides of record northward along the coast from Cape Hatteras to Cape Cod have been produced by hurricanes. From time to time our “northeasters”, which are extra-tropical storms, may also cause millions of dollars of damage along the Atlantic coast between Miami, Fla., and Eastport, Me.
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Ray, Richard D. "Decadal Climate Variability: Is There a Tidal Connection?" Journal of Climate 20, no. 14 (July 15, 2007): 3542–60. http://dx.doi.org/10.1175/jcli4193.1.
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Abstract A possible connection between oceanic tides and climate variability arises from modulations in tidally induced vertical mixing. The idea is reexamined here with emphasis on near-decadal time scales. Occasional extreme tides caused by unusually favorable alignments of the moon and sun are unlikely to influence decadal climate, since these tides are of short duration and, in fact, are barely larger than the typical spring tide near lunar perigee. The argument by Keeling and Whorf in favor of extreme tides is further handicapped by an insufficiently precise catalog of extreme tides. A more plausible connection between tides and near-decadal climate is through “harmonic beating” of nearby tidal spectral lines. The 18.6-yr modulation of diurnal tides is the most likely to be detectable. Possible evidence for this is reviewed. Some of the most promising candidates rely on temperature data in the vicinity of the North Pacific Ocean where diurnal tides are large, but definitive detection is hindered by the shortness of the time series. Paleoclimate temperature data deduced from tree rings are suggestive, but one of the best examples shows a phase reversal, which is evidence against a tidal connection.
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Ray, R. D., and R. M. Ponte. "Barometric tides from ECMWF operational analyses." Annales Geophysicae 21, no. 8 (August 31, 2003): 1897–910. http://dx.doi.org/10.5194/angeo-21-1897-2003.
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Abstract. The solar diurnal and semidiurnal tidal oscillations in surface pressure are extracted from the operational analysis product of the European Centre for Medium Range Weather Forecasting (ECMWF). For the semidiurnal tide this involves a special temporal interpolation, following Van den Dool et al. (1997). The resulting tides are compared with a "ground truth" tide data set, a compilation of well-determined tide estimates deduced from many long time series of station barometer measurements. These comparisons show that the ECMWF (analysis) tides are significantly more accurate than the tides deduced from two other widely available reanalysis products. Spectral analysis of ECMWF pressure series shows that the tides consist of sharp central peaks with modulating sidelines at integer multiples of 1 cycle/year, superimposed on a broad cusp of stochastic energy. The integrated energy in the cusp dominates that of the side-lines. This complicates the development of a simple empirical model that can characterize the full temporal variability of the tides.Key words. Meteorology and atmospheric dynamics (waves and tides)
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CHANG, YUAN-YING, CHENG-KEN HUANG, CHI-FANG CHEN, and SEN JAN. "STUDY OF TRANSMISSION LOSS VARIATION AFFECTED BY INTERNAL TIDES IN THE SEA AREA NORTHEAST OF TAIWAN." Journal of Computational Acoustics 20, no. 01 (March 2012): 1250002. http://dx.doi.org/10.1142/s0218396x1100450x.
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Internal tides can cause density and sound speed fluctuations in the ocean, and the thickness of the mixing layer can fluctuate in short periods of time. This phenomenon affects underwater sound propagation and induces transmission loss variations. In the sea area northeast of Taiwan, regular internal tide activity is observed. The topography and sediment there are also complex, which makes the effect on transmission loss by internal tides even more complicated. This paper studies how transmission loss variation is affected by internal tides in the sea area northeast of Taiwan. The hydrographic fields with influence from the internal tides are provided by an experiment survey on the 4th of September, 2008 and a 3-D tide model. The transmission loss comparison between different thicknesses of the mixing layer in the internal tide fields is shown. Furthermore, the correlation coefficient is calculated and shows that layer depth and transmission loss have a medium to high negative correlation in the upper water column during the summer spring-tide period, and a low to medium negative correlation during the summer neap-tide period.
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Lee, Min-Sun, Kyung-Ae Park, and Fiorenza Micheli. "Derivation of Red Tide Index and Density Using Geostationary Ocean Color Imager (GOCI) Data." Remote Sensing 13, no. 2 (January 16, 2021): 298. http://dx.doi.org/10.3390/rs13020298.
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Red tide causes significant damage to marine resources such as aquaculture and fisheries in coastal regions. Such red tide events occur globally, across latitudes and ocean ecoregions. Satellite observations can be an effective tool for tracking and investigating red tides and have great potential for informing strategies to minimize their impacts on coastal fisheries. However, previous satellite-based red tide detection algorithms have been mostly conducted over short time scales and within relatively small areas, and have shown significant differences from actual field data, highlighting a need for new, more accurate algorithms to be developed. In this study, we present the newly developed normalized red tide index (NRTI). The NRTI uses Geostationary Ocean Color Imager (GOCI) data to detect red tides by observing in situ spectral characteristics of red tides and sea water using spectroradiometer in the coastal region of Korean Peninsula during severe red tide events. The bimodality of peaks in spectral reflectance with respect to wavelengths has become the basis for developing NRTI, by multiplying the heights of both spectral peaks. Based on the high correlation between the NRTI and the red tide density, we propose an estimation formulation to calculate the red tide density using GOCI data. The formulation and methodology of NRTI and density estimation in this study is anticipated to be applicable to other ocean color satellite data and other regions around the world, thereby increasing capacity to quantify and track red tides at large spatial scales and in real time.
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Baranov, A. A., S. V. Baranov, and P. N. Shebalin. "A quantitative estimate of the effects of sea tides on aftershock activity: Kamchatka." Вулканология и сейсмология, no. 1 (March 4, 2019): 67–82. http://dx.doi.org/10.31857/s0203-03062019167-72.
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The issue of whether tidal forces really affect seismicity has been raised many times in the literature. Nevertheless, even though there seems to be a kind of consensus that such effects do exist, no quantitative estimates are available to relate tide parameters to changes in the level of seismic activity. Such estimation for aftershocks of large earthquakes near Kamchatka is the goal of the present study. We consider the influence on seismicity due to ocean tides only, because their effects are stronger than those of solid earth tides. Accordingly, we only consider earthquakes that occurred in the ocean. One important feature that distinguishes the present study from most other such research consists in the fact that we study the height of ocean tides and its derivative rather than tidal phases as the decisive factors. We considered 16 aftershock sequences of earthquakes near Kamchatka with magnitudes of 6 or greater. We also examined shallow background earthquakes along the coast of Kamchatka. Our basic model of aftershock rate was the Omori–Utsu law. The background seismicity distribution was assumed to be uniform over time. In both of these cases we used the actual distributions in space. The heights of ocean tides were estimated using the FES 2004 model (Lyard et al., 2006). The variation in activity from what the basic model assumes in relation to tidal wave height and its time derivative was estimated by the method of differential probability gain. The main practical result of this study consists in estimates of averaged differential probability gain functions for aftershock rate with respect to both of theconsidered factors. These estimates can be used for earthquake hazard assessment from aftershocks with ocean tides incorporated. The results of our analysis show a persistent tendency of aftershock rate increasing during periods when the ocean tide decreased at a high rate. For the background events, we found a typical tendency of event rate increasing when the ocean tide decreased with high tidal amplitudes. The difference in the main factors that affect aftershocks and background seismicity suggest the inference that the effects of tides on aftershocks are more likely to be direct dynamic initiation of events during high strain rates, while the effects on the backgroundevents were static in character.
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Baranov, A. A., S. V. Baranov, and P. N. Shebalin. "A quantitative estimate of the effects of sea tides on aftershock activity: Kamchatka." Вулканология и сейсмология, no. 1 (March 4, 2019): 67–72. http://dx.doi.org/10.31857/s0205-96142019167-72.
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The issue of whether tidal forces really affect seismicity has been raised many times in the literature. Nevertheless, even though there seems to be a kind of consensus that such effects do exist, no quantitative estimates are available to relate tide parameters to changes in the level of seismic activity. Such estimation for aftershocks of large earthquakes near Kamchatka is the goal of the present study. We consider the influence on seismicity due to ocean tides only, because their effects are stronger than those of solid earth tides. Accordingly, we only consider earthquakes that occurred in the ocean. One important feature that distinguishes the present study from most other such research consists in the fact that we study the height of ocean tides and its derivative rather than tidal phases as the decisive factors. We considered 16 aftershock sequences of earthquakes near Kamchatka with magnitudes of 6 or greater. We also examined shallow background earthquakes along the coast of Kamchatka. Our basic model of aftershock rate was the Omori–Utsu law. The background seismicity distribution was assumed to be uniform over time. In both of these cases we used the actual distributions in space. The heights of ocean tides were estimated using the FES 2004 model (Lyard et al., 2006). The variation in activity from what the basic model assumes in relation to tidal wave height and its time derivative was estimated by the method of differential probability gain. The main practical result of this study consists in estimates of averaged differential probability gain functions for aftershock rate with respect to both of theconsidered factors. These estimates can be used for earthquake hazard assessment from aftershocks with ocean tides incorporated. The results of our analysis show a persistent tendency of aftershock rate increasing during periods when the ocean tide decreased at a high rate. For the background events, we found a typical tendency of event rate increasing when the ocean tide decreased with high tidal amplitudes. The difference in the main factors that affect aftershocks and background seismicity suggest the inference that the effects of tides on aftershocks are more likely to be direct dynamic initiation of events during high strain rates, while the effects on the backgroundevents were static in character.
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Tursina, Tursina, Syamsidik Syamsidik, Shigeru Kato, and Mochammad Afifuddin. "Influence of Tides Level on Tsunami Hydrodynamic in Banda Aceh, Indonesia." International Journal of Disaster Management 6, no. 3 (March 18, 2024): 313–26. http://dx.doi.org/10.24815/ijdm.v6i2.34538.
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Tides are the dominant physical process in the coastal environment. During high tide, water from the ocean flows through the bays and estuaries, causing inundation and raising water elevation. When low tides condition, the water level becomes lower than average and recedes into the sea. This process continues for a long day. Tsunami waves will interact with all coastal processes and affect the hydrodynamic forces of tsunami waves. In the deep sea, tides do not significantly influence wave propagation. However, in the shallow water zone, tides can change tsunami heights and affect the extent of inundation. Tides are usually ignored in tsunami hazard analysis. This would be an underestimate of the tsunami hazard calculation. This study aims to investigate tides' influence on tsunami runup hydrodynamics in Banda Aceh. The potential tsunami from an earthquake in the Aceh-Andaman subduction zone is modeled using COMCOT (Cornell Multi Grid Coupled Tsunami Model) with magnitudes Mw 9.2, 8.6, and 8.2. We simulated the response of the three earthquake magnitudes on two different types of high and low tides. Several virtual gauges were placed to observe the tsunami height. Virtual gauges were also used to observe the tsunami arrival time at four tsunami escape buildings in Banda Aceh: the Ulee Lheue escape building, the Deah Glumpang escape building, the Alue Deah Teungoh escape building, and the Lambung escape building. The results show that the highest tide amplifies the tsunami inundation will be extended to about 30% farther inland compared to the condition if the tsunami occur during mean sea level condition. The interactions between tsunami and high tide significantly shorten tsunami arrival time on small magnitude tsunamis and are not significant in a large tsunami. This information is useful for enhancing early warning systems and evacuation procedures that can be adjusted to the tidal conditions in the study area.
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Sakamoto, K., H. Tsujino, H. Nakano, M. Hirabara, and G. Yamanaka. "A practical scheme to introduce explicit tidal forcing into an OGCM." Ocean Science 9, no. 6 (December 13, 2013): 1089–108. http://dx.doi.org/10.5194/os-9-1089-2013.
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Abstract. A practical scheme is proposed to explicitly introduce tides into ocean general circulation models (OGCM). In this scheme, barotropic linear response to the tidal forcing is calculated by the time differential equations modified for ocean tides, instead of the original barotropic equations of an OGCM. This allows for the usage of various parameterizations specified for tides, such as the self-attraction/loading (SAL) effect and energy dissipation due to internal tides, without unintentional violation of the original dynamical balances in an OGCM. Meanwhile, secondary nonlinear effects of tides, e.g., excitation of internal tides and advection by tidal currents, are fully represented within the framework of the original OGCM equations. That is, this scheme drives the OGCM by the barotropic linear tidal currents which are predicted progressively by a tuned tide model, instead of the equilibrium tide potential, without large additional numerical costs. We incorporated this scheme into Meteorological Research Institute Community Ocean Model and executed test experiments with a low-resolution global model. The results showed that the model can simulate both the non-tidal circulations and the tidal motion simultaneously. Owing to the usage of tidal parameterizations such as a SAL term, a root-mean-squared error in the tidal heights is found to be as small as 10.0 cm, which is comparable to that of elaborately tuned tide models. In addition, analysis of the speed and energy of the barotropic tidal currents is found to be consistent with that of past tide studies. The model also showed active excitement of internal tides and tidal mixing. In the future, the impacts of internal tides and tidal mixing should be examined using a model with a finer resolution, since explicit and precise introduction of tides into an OGCM is a significant step toward the improvement of ocean models.
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Boesch, Andreas, and Sylvin Müller-Navarra. "Reassessment of long-period constituents for tidal predictions along the German North Sea coast and its tidally influenced rivers." Ocean Science 15, no. 5 (October 18, 2019): 1363–79. http://dx.doi.org/10.5194/os-15-1363-2019.
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Abstract. The harmonic representation of inequalities (HRoI) is a procedure for tidal analysis and prediction that combines aspects of the non-harmonic and the harmonic method. With this technique, the deviations of heights and lunitidal intervals, especially of high and low waters, from their respective mean values are represented by superpositions of long-period tidal constituents. This article documents the preparation of a constituents list for the operational application of the harmonic representation of inequalities. Frequency analyses of observed heights and lunitidal intervals of high and low water from 111 tide gauges along the German North Sea coast and its tidally influenced rivers have been carried out using the generalized Lomb–Scargle periodogram. One comprehensive list of partial tides is realized by combining the separate frequency analyses and by applying subsequent improvements, e.g. through manual inspections of long time series data. The new set of 39 partial tides largely confirms the previously used set with 43 partial tides. Nine constituents are added and 13 partial tides, mostly in the close neighbourhood of strong spectral components, are removed. The effect of these changes has been studied by comparing predictions with observations from 98 tide gauges. Using the new set of constituents, the standard deviations of the residuals are reduced on average by 2.41 % (times) and 2.30 % (heights) for the year 2016. The new set of constituents will be used for tidal analyses and predictions starting with the German tide tables for the year 2020.
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Sakamoto, K., H. Tsujino, H. Nakano, M. Hirabara, and G. Yamanaka. "A practical scheme to introduce explicit tidal forcing into OGCM." Ocean Science Discussions 10, no. 2 (March 7, 2013): 473–517. http://dx.doi.org/10.5194/osd-10-473-2013.
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Abstract. A practical scheme is proposed to introduce tides explicitly into ocean general circulation models (OGCM). In this scheme, barotropic linear response to the tidal forcing is calculated by the time differential equations modified for ocean tides, instead of the original barotropic equations of OGCM. This allows usage of various parameterizations specified for tides, such as the self attraction/loading (SAL) effect and energy dissipation due to internal tides, without unintentional violation of the original dynamical balances in OGCM. Meanwhile, secondary nonlinear effects of tides, e.g. excitation of internal tides and advection by tidal currents, are fully represented in the framework of the original OGCM equations. That is, this scheme drives OGCM by the barotropic linear tidal currents which are predicted progressively by a well-tuned tide model, instead of the equilibrium tide potential, without large additional numerical costs. We incorporated this scheme into Meteorological Research Institute Community Ocean Model and executed test experiments with a low-resolution global model. The results showed that the model can simulate both of non-tidal circulations and tidal motion simultaneously. Owing to usage of tidal parameterizations such as a SAL term, a root mean square error in the tidal heights was as small as 10.0 cm, which is comparable to tide models tuned elaborately. In addition, analysis of speed and energy of the barotropic tidal currents was consistent with past tide studies. The model also showed active excitement of internal tides and tidal mixing. Their impacts should be examined using a model with a finer resolution in future, since explicit and precise introduction of tides into OGCM is a significant step toward upgrade of ocean modeling.
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Martini, Kim I., Matthew H. Alford, Eric Kunze, Samuel M. Kelly, and Jonathan D. Nash. "Internal Bores and Breaking Internal Tides on the Oregon Continental Slope." Journal of Physical Oceanography 43, no. 1 (January 1, 2013): 120–39. http://dx.doi.org/10.1175/jpo-d-12-030.1.
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Abstract Observations of breaking internal tides on the Oregon continental slope during a 40-day deployment of 5 moorings along 43°12′N are presented. Remotely generated internal tides shoal onto the slope, steepen, break, and form turbulent bores that propagate upslope independently of the internal tide. A high-resolution snapshot of a single bore is captured from lowered acoustic Doppler current profilers (LADCP)/CTD profiles in a 25-h time series at 1200 m. The bore is cold, salty, over 100 m tall, and has a turbulent head where instantaneous dissipation rates are enhanced (ε > 10−6 W kg−1) and sediment is resuspended. At the two deepest slope moorings (1452 and 1780 m), similar borelike phenomena are observed in near-bottom high-resolution temperature time series. Mean dissipation rates and diapycnal diffusivities increase by a factor of 2 when bores are present ( W kg−1 and m s−1) and observed internal tides are energetic enough to drive these enhanced dissipation rates. Globally, the authors estimate an average of 1.3 kW m−1 of internal tide energy flux is directed onto continental slopes. On the Oregon slope, internal tide fluxes are smaller, suggesting that it is a relatively weak internal tide sink. Mixing associated with the breaking of internal tides is therefore likely to be larger on other continental slopes.
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Forward, Richard B., Humberto Diaz, and Jonathan H. Cohen. "The tidal rhythm in activity of the mole crab Emerita talpoida." Journal of the Marine Biological Association of the United Kingdom 85, no. 4 (June 27, 2005): 895–901. http://dx.doi.org/10.1017/s0025315405011860.
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The mole crab Emerita talpoida occurs in the swash zone of sandy beaches. Although crabs move with the tide, field studies found that the smaller crabs are distributed higher intertidally than the larger crabs. The present study tested the hypothesis that the rhythm, timing of activity, and activity amplitude with respect to tides would be different among megalopae, juveniles, small females, small males, mature males and large ovigerous females and underlie the observed field distributions. Activity of individuals in columns was observed under constant conditions with a video system and quantified as the number of ascents from the sand each 0·5 h. All life history stages had a circatidal rhythm in vertical swimming with median free running period lengths near 12·4 h and activity peaks after the time of high tide. Period length and time of activity peaks did not differ significantly among the life history stages. Activity amplitude was related to tidal amplitude of consecutive high tides at the collection site. Larger crabs had greatest activity after the lower amplitude high tides whereas small crabs had equal activity amplitude on consecutive tides. The test hypothesis was partially supported because the difference in activity amplitude predicts an oscillation between overlapping distributions of small and large crabs after low amplitude high tides, with the smaller crabs distributed higher on the beach after high amplitude high tides. The rhythm was not affected by a light:dark cycle and could be entrained by mechanical agitation.
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Goring, Derek G., and Roy A. Walters. "Ocean‐tide loading and Earth tides around New Zealand." New Zealand Journal of Marine and Freshwater Research 36, no. 2 (June 2002): 299–309. http://dx.doi.org/10.1080/00288330.2002.9517087.
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Kelly, S. M., and J. D. Nash. "Internal-tide generation and destruction by shoaling internal tides." Geophysical Research Letters 37, no. 23 (December 2010): n/a. http://dx.doi.org/10.1029/2010gl045598.
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Lin, Lei, Hao Liu, Xiaomeng Huang, Qingjun Fu, and Xinyu Guo. "Effect of tides on river water behavior over the eastern shelf seas of China." Hydrology and Earth System Sciences 26, no. 20 (October 18, 2022): 5207–25. http://dx.doi.org/10.5194/hess-26-5207-2022.
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Abstract. Rivers carry large amounts of freshwater and terrestrial material into shelf seas, which is an important part of the global water and biogeochemical cycles. The earth system model or climate model is an important instrument for simulating and projecting the global water cycle and climate change, in which tides however are commonly removed. For a better understanding of the potential effect of the absence of tides in the simulation of the water cycle, this study compared the results of a regional model with and without considering tides, and evaluated the effect of tides on the behavior of three major rivers (i.e., the Yellow, Yalujiang, and Changjiang rivers) water in the eastern shelf seas of China from the perspectives of transport pathways, timescales, and water concentration. The results showed that the tides induced more dispersed transport for the water of the Yellow and Yalujiang rivers, but more concentrated transport for the Changjiang River water. The effect of tides on the transit areas of the Yellow, Yalujiang, and Changjiang rivers was 13 %, 40 %, and 21 %, respectively. The annual mean water age and transit time of the three rivers in the model with tides were several (∼ 2–10) times higher than those in the no-tide model, suggesting that tides dramatically slow the river water transport and export rate over the shelf. By slowing the river water export, tides induced a three-fold increase in river water concentration and a decrease in shelf seawater salinity by > 1. Moreover, the effect of tides on river behavior was stronger in relatively enclosed seas (i.e., the Bohai and Yellow seas) than in relatively open seas (i.e., the East China Sea). The change in the shelf currents induced by tides is the main cause of the difference in the river water behavior between the two model runs. Tides can increase bottom stress and thus weaken shelf currents and decrease the water transport timescales. The improvement in tidal parameterization in the no-tide model in the simulation of river water behavior was very limited. Given the important role of river runoff on the global water cycle and the effect of changes in river water behavior on ocean carbon cycling, it is important to include the tidal effect in earth system models to improve their projection accuracy.
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Khalid, Muhammad, Rizalul Akram, and Khairul Muttaqin. "Sistem Monitoring Pasang Surut Air Laut Berbasis Web Menggunakan Fuzzy Logic Pada Kuala Langsa." Journal of Information and Technology 2, no. 2 (September 5, 2022): 65–69. http://dx.doi.org/10.32938/jitu.v2i2.3254.
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Abstract - Tides are a phenomenon of periodic and periodic ups and downs of sea level movements. The tidal period is the time between the crest of a wave to the crest of the next wave, the time of the tidal period varies from 12 hours 25 minutes to 24 hours 50 minutes. Information about tides is very useful for activities related to the marine world. In the area of Kuala Langsa, tides often occur, fishermen and anglers in Kuala Langsa only rely on the poles of residents' houses to determine the time of the tide. The system is made useful so that fishermen and anglers can find out the time and state of the tides using smartphones, by creating a “Sea Tidal Monitoring System using Ultrasonic Sensors and nodeMCU which can provide results of monitoring the time and tidal status in Kuala Langsa and will displayed on a Web page”. Ultrasonic sensors can detect well and can provide tidal data to be displayed on a web page and can be accessed using smartphones and other devices during the testing period in Kuala Langsa village, Langsa City with 62.5% success being tested.
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Nash, Jonathan D., Samuel M. Kelly, Emily L. Shroyer, James N. Moum, and Timothy F. Duda. "The Unpredictable Nature of Internal Tides on Continental Shelves." Journal of Physical Oceanography 42, no. 11 (November 1, 2012): 1981–2000. http://dx.doi.org/10.1175/jpo-d-12-028.1.
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Abstract Packets of nonlinear internal waves (NLIWs) in a small area of the Mid-Atlantic Bight were 10 times more energetic during a local neap tide than during the preceding spring tide. This counterintuitive result cannot be explained if the waves are generated near the shelf break by the local barotropic tide since changes in shelfbreak stratification explain only a small fraction of the variability in barotropic to baroclinic conversion. Instead, this study suggests that the occurrence of strong NLIWs was caused by the shoaling of distantly generated internal tides with amplitudes that are uncorrelated with the local spring-neap cycle. An extensive set of moored observations show that NLIWs are correlated with the internal tide but uncorrelated with barotropic tide. Using harmonic analysis of a 40-day record, this study associates steady-phase motions at the shelf break with waves generated by the local barotropic tide and variable-phase motions with the shoaling of distantly generated internal tides. The dual sources of internal tide energy (local or remote) mean that shelf internal tides and NLIWs will be predictable with a local model only if the locally generated internal tides are significantly stronger than shoaling internal tides. Since the depth-integrated internal tide energy in the open ocean can greatly exceed that on the shelf, it is likely that shoaling internal tides control the energetics on shelves that are directly exposed to the open ocean.
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Mariote, Leonardo E., Claudia Bauzer Medeiros, Ricardo da Silva Torres, and Lucas M. Bueno. "TIDES—a new descriptor for time series oscillation behavior." GeoInformatica 15, no. 1 (June 18, 2010): 75–109. http://dx.doi.org/10.1007/s10707-010-0112-5.
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Roberts, Claire. ""Time and Tides: Xiao Lu’s Recursive Art, 1989-2019"." ISSUE 12 (2023): 67–79. http://dx.doi.org/10.33671/iss12rob.
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Gargett, Ann E., and Dana K. Savidge. "Separation of Short Time Series of Currents into “Fluctuations,” “Tides,” and “Mean” Flow." Journal of Atmospheric and Oceanic Technology 33, no. 5 (May 2016): 1089–95. http://dx.doi.org/10.1175/jtech-d-15-0232.1.
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AbstractWith standard low-frequency velocity data from current meter moorings, pressure gradient–driven mean flow is determined by low-pass filtering, while tides are estimated by fitting tidal constituents, with accuracy and numbers of constituents determined by record length. With the advent of higher-frequency measurements from cabled coastal ocean observatories, current data also include supertidal variability (fluctuation) associated with a variety of turbulent and internal wave processes. To examine the relationships of such fluctuations to variability of the tides and/or potentially time-variable mean flows within which they are embedded, it is highly desirable to find a method whereby these flow components can be separated over relatively short periods of intensified event-scale forcing. A method is presented that first isolates “fluctuations” and then separates the remaining longer time-scale variability into “tides” and a remaining “mean,” without recourse to extraction of a fitted tide with the error inherent in such a fit over short data records.
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Di Nunno, Fabio, Francesco Granata, Rudy Gargano, and Giovanni de Marinis. "Forecasting of Extreme Storm Tide Events Using NARX Neural Network-Based Models." Atmosphere 12, no. 4 (April 17, 2021): 512. http://dx.doi.org/10.3390/atmos12040512.
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The extreme values of high tides are generally caused by a combination of astronomical and meteorological causes, as well as by the conformation of the sea basin. One place where the extreme values of the tide have a considerable practical interest is the city of Venice. The MOSE (MOdulo Sperimentale Elettromeccanico) system was created to protect Venice from flooding caused by the highest tides. Proper operation of the protection system requires an adequate forecast model of the highest tides, which is able to provide reliable forecasts even some days in advance. Nonlinear Autoregressive Exogenous (NARX) neural networks are particularly effective in predicting time series of hydrological quantities. In this work, the effectiveness of two distinct NARX-based models was demonstrated in predicting the extreme values of high tides in Venice. The first model requires as input values the astronomical tide, barometric pressure, wind speed, and direction, as well as previously observed sea level values. The second model instead takes, as input values, the astronomical tide and the previously observed sea level values, which implicitly take into account the weather conditions. Both models proved capable of predicting the extreme values of high tides with great accuracy, even greater than that of the models currently used.
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Kerry, Colette G., Brian S. Powell, and Glenn S. Carter. "Quantifying the Incoherent M2 Internal Tide in the Philippine Sea." Journal of Physical Oceanography 46, no. 8 (August 2016): 2483–91. http://dx.doi.org/10.1175/jpo-d-16-0023.1.
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AbstractThe baroclinic tides are a crucial source of mixing energy into the deep ocean; however, the incoherent portion of the spectrum is not well examined because it is difficult to observe. This study estimates the coherent and incoherent M2 internal tide energy fluxes in the Philippine Sea using a primitive equation model that resolves the M2 barotropic and baroclinic tides and the time-evolving atmospherically forced eddying circulation. A time-mean, incoherent, internal tide energy flux of 25% of the coherent energy flux is found to emanate eastward into the Philippine Sea from the Luzon Strait and a time-mean incoherent portion of 30% of the coherent energy flux propagates westward into the South China Sea (SCS). The incoherent internal tide energy results from baroclinic tide generation and propagation variability. Quantifying the incoherent portion estimates the energy missing from altimeter-derived or line-integral acoustic measurements and places short-lived, in situ observations in the context of variability.
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Zhao, Zhongxiang, Matthew H. Alford, Ren-Chieh Lien, Michael C. Gregg, and Glenn S. Carter. "Internal Tides and Mixing in a Submarine Canyon with Time-Varying Stratification." Journal of Physical Oceanography 42, no. 12 (December 1, 2012): 2121–42. http://dx.doi.org/10.1175/jpo-d-12-045.1.
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Abstract The time variability of the energetics and turbulent dissipation of internal tides in the upper Monterey Submarine Canyon (MSC) is examined with three moored profilers and five ADCP moorings spanning February–April 2009. Highly resolved time series of velocity, energy, and energy flux are all dominated by the semidiurnal internal tide and show pronounced spring-neap cycles. However, the onset of springtime upwelling winds significantly alters the stratification during the record, causing the thermocline depth to shoal from about 100 to 40 m. The time-variable stratification must be accounted for because it significantly affects the energy, energy flux, the vertical modal structures, and the energy distribution among the modes. The internal tide changes from a partly horizontally standing wave to a more freely propagating wave when the thermocline shoals, suggesting more reflection from up canyon early in the observational record. Turbulence, computed from Thorpe scales, is greatest in the bottom 50–150 m and shows a spring-neap cycle. Depth-integrated dissipation is 3 times greater toward the end of the record, reaching 60 mW m−2 during the last spring tide. Dissipation near a submarine ridge is strongly tidally modulated, reaching 10−5 W kg−1 (10–15-m overturns) during spring tide and appears to be due to breaking lee waves. However, the phasing of the breaking is also affected by the changing stratification, occurring when isopycnals are deflected downward early in the record and upward toward the end.
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de Vries, Tity. "Cinematic Rotterdam. The Times and Tides of a Modern City." Historical Journal of Film, Radio and Television 32, no. 4 (December 2012): 644–46. http://dx.doi.org/10.1080/01439685.2012.728329.
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Al Mohit, Md Abdul, Md. Towhiduzzaman, and Mst Rabiba Khatun. "Development of A Novel Conceptual and Calculative Method for the Prediction of Tide within the Bay of Bengal." European Journal of Mathematics and Statistics 3, no. 4 (August 23, 2022): 54–61. http://dx.doi.org/10.24018/ejmath.2022.3.4.134.
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Ebb and flow of seawater at regular intervals under the influence of gravitational forces from outside the earth is called tides. This study sheds light on how to measure tides through a new kind of innovative method. This method can be used to measure tides at new locations based on a known tide station. Some parameters play an important role in measuring tides, such as datum information, mean sea level (MSL), mean high water springs (MHWS), mean low water springs (MLWS) and so on. This fancy method is a computational process that relies on observable data and other factors. This innovative method of measuring tides helps to get accurate information in less time and at less cost. From this study we find that the results obtained in our study are in good agreement with the results obtained by other methods and the observed data.
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von Storch, Jin-Song, Eileen Hertwig, Veit Lüschow, Nils Brüggemann, Helmuth Haak, Peter Korn, and Vikram Singh. "Open-ocean tides simulated by ICON-O, version icon-2.6.6." Geoscientific Model Development 16, no. 17 (September 8, 2023): 5179–96. http://dx.doi.org/10.5194/gmd-16-5179-2023.
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Abstract. This paper evaluates barotropic tides simulated by a newly developed multi-layer ocean general circulation, ICON-O, and assesses processes and model configurations that can impact the quality of the simulated tides. Such an investigation is crucial for applications addressing internal tides that are much more difficult to evaluate than the barotropic tides. Although not specially tuned for tides and not constrained by any observations, ICON-O is capable of producing the main features of the open-ocean barotropic tides as described by the geographical distributions of amplitude, phase, and amphidromic points. An error analysis shows, however, that the open-ocean tides simulated by ICON-O are less accurate than those simulated by two other ocean general circulation models (OGCMs), especially when not properly adjusting the time step and the parameters used in the time-stepping scheme. Based on a suite of tidal experiments, we show that an increase in horizontal resolution only improves tides in shallow waters. Relevant for using ICON-O with its telescoping grid capacity, we show that spatial inhomogeneity does not deteriorate the quality of the simulated tides. We further show that implementing a parameterization of topographic wave drag improves the quality of the simulated tides in deep ocean independent of the model configuration used, whereas the implementation of a self-attraction and loading (SAL) parameterization in a low-resolution (40 km) version of ICON-O degrades the quality of tides in shallow ocean. Finally, we show that the quality of tides simulated by ICON-O with low resolution (40 km) can be significantly improved by adjusting the time step or the parameters in the time-stepping scheme used for obtaining the model solution.
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Matte, Pascal, David A. Jay, and Edward D. Zaron. "Adaptation of Classical Tidal Harmonic Analysis to Nonstationary Tides, with Application to River Tides." Journal of Atmospheric and Oceanic Technology 30, no. 3 (March 1, 2013): 569–89. http://dx.doi.org/10.1175/jtech-d-12-00016.1.
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Abstract One of the most challenging areas in tidal analysis is the study of nonstationary signals with a tidal component, as they confront both current analysis methods and dynamical understanding. A new analysis tool has been developed, NS_TIDE, adapted to the study of nonstationary signals, in this case, river tides. It builds the nonstationary forcing directly into the tidal basis functions. It is implemented by modification of T_TIDE; however, certain concepts, particularly the meaning of a constituent and the Rayleigh criterion, are redefined to account for the smearing effects on the tidal spectral lines by nontidal energy. An error estimation procedure is included that constructs a covariance matrix of the regression coefficients, based on either an uncorrelated or a correlated noise model. The output of NS_TIDE consists of time series of subtidal water levels [mean water level (MWL)] and tidal properties (amplitudes and phases), expressed in terms of external forcing functions. The method was tested using records from a station on the Columbia River, 172 km from the ocean entrance, where the tides are strongly altered by river flow. NS_TIDE hindcast explains 96.4% of the signal variance with a root-mean-square error of 0.165 m obtained from 288 parameters, far better than traditional harmonic analysis (38.5%, 0.604 m, and 127 parameters). While keeping the benefits of harmonic analysis, its advantages compared to existing tidal analysis methods include its capacity to distinguish frequencies within tidal bands without losing resolution in the time domain or data at the endpoints of the time series.
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Gou, Xiaoxiao, Huidi Liang, Tinglu Cai, Xinkai Wang, Yining Chen, and Xiaoming Xia. "The Impact of Coastline and Bathymetry Changes on the Storm Tides in Zhejiang Coasts." Journal of Marine Science and Engineering 11, no. 9 (September 20, 2023): 1832. http://dx.doi.org/10.3390/jmse11091832.
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Coastal evolutions are expected to have a significant impact on storm tides, disproportionately aggravating coastal flooding. In this study, we utilize a nested storm tide model to provide an integrated investigation of storm tide responses to changes in coastline and bathymetry along the Zhejiang coasts. We selected coastline and bathymetry data from 1980 and 2016, as well as data from three typical typhoon events (i.e., Winnie, Haikui, and Chan-hom) for simulating the storm surge processes. The results indicate that changes in the coastline and bathymetry from 1980 to 2016 have resulted in an increase in storm tides in the northern part and a decrease in the central part of Zhejiang. Specifically, storm tides in Hangzhou Bay have increased significantly, with an average increase of about 0.3 m in the maximum storm tides primarily attributed to coastline changes. On the contrary, in smaller basins like Sanmen Bay, while reclamation itself has reduced peak storm surges, rapid siltation has consequently exacerbated the storm surge. By decomposing storm tides into astronomical tides and storm surges, we discovered that the change in tidal levels was twice as significant as the surge change. Moreover, the nonlinear tide–surge interaction was nearly four times that of the pure surge, significantly contributing to storm surge variation. Alterations in the momentum balance reveal that the water depth-induced bottom friction and wind stress increase contributes to the local enlargement of storm tides at the bay head, while the coastline changes exaggerate nearshore storm tides through an increase in the advection term.
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Zhao, Zhongxiang. "Development of the Yearly Mode-1 M2 Internal Tide Model in 2019." Journal of Atmospheric and Oceanic Technology 39, no. 4 (April 2022): 463–78. http://dx.doi.org/10.1175/jtech-d-21-0116.1.
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Abstract The yearly mode-1 M2 internal tide model in 2019 is constructed using sea surface height measurements made by six concurrent satellite altimetry missions: Jason-3, Sentinel-3A, Sentinel-3B, CryoSat-2, Haiyang-2A, and SARAL/AltiKa. The model is developed following a three-step procedure consisting of two rounds of plane wave analysis with a spatial bandpass filter in between. Prior mesoscale correction is made on the altimeter data using AVISO gridded mesoscale fields. The model is labeled Y2019, because it represents the 1-yr-coherent internal tide field in 2019. In contrast, the model developed using altimeter data from 1992 to 2017 is labeled MY25, because it represents the multiyear-coherent internal tide field in 25 years. Thanks to the new mapping technique, model errors in Y2019 are as low as those in MY25. Evaluation using independent altimeter data confirms that Y2019 reduces slightly less variance (∼6%) than MY25. Further analysis reveals that the altimeter data from five missions (without Jason-3) can yield an internal tide model of almost the same quality. Comparing Y2019 and MY25 shows that mode-1 M2 internal tides are subject to significant interannual variability in both amplitude and phase, and their interannual variations are a function of location. Along southward internal tides from Amukta Pass, the energy flux in Y2019 is 2 times larger and the phase speed is about 1.1% faster. This mapping technique has been applied successfully to 2017 and 2018. This work demonstrates that yearly internal tides can be observed by concurrent altimetry missions and their interannual variations can be determined. Significance Statement This work is motivated to study the interannual variations of internal tides using observation-based yearly internal tide models from satellite altimetry. Previous satellite observations of internal tides are usually based on 25 years of altimeter data from 1993 to 2017. The yearly subsetted altimeter data are short, so that the resultant yearly models are overwhelmed by noise. A new mapping technique is developed and demonstrated in this paper. It paves a path to study the interannual and decadal variations of internal tides on a global scale and monitor the global ocean changes by tracking long-range internal tides.
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Zaron, E. D. "Nonstationary Internal Tides Observed Using Dual-Satellite Altimetry." Journal of Physical Oceanography 45, no. 9 (September 2015): 2239–46. http://dx.doi.org/10.1175/jpo-d-15-0020.1.
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AbstractDual-satellite crossover data from the Jason-2 and Cryosat-2 altimeter missions are used in a novel approach to quantify stationary and nonstationary tides from time-lagged mean square sea surface height (SSH) differences, computed for lags from 1 to 1440 h (60 days). The approach is made feasible by removing independent estimates of the stationary tide and mesoscale SSH variance, which greatly reduces the sampling error of the SSH statistics. For the semidiurnal tidal band, the stationary tidal variance is approximately 0.73 cm2, and the nonstationary variance is about 0.33 cm2, or 30% of the total. The temporal correlation of the nonstationary tide is examined by complex demodulation and found to be oscillatory with first 0 crossing at 400 h (17 days). Because a significant fraction of the time-variable mesoscale signal is resolved at time scales of roughly 150 h by the present constellation of satellite altimeters, the results suggest that it may be feasible to predict the nonstationary tide from modulations of the resolved mesoscale, thus enhancing the efficacy of tidal corrections for planned wide-swath altimeters such as the Surface Water and Ocean Topography (SWOT) mission.
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Richter, Andreas, Søren Rysgaard, Reinhard Dietrich, John Mortensen, and Dorthe Petersen. "Coastal tides in West Greenland derived from tide gauge records." Ocean Dynamics 61, no. 1 (September 26, 2010): 39–49. http://dx.doi.org/10.1007/s10236-010-0341-z.
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Subrahmanyam, Bulusu, V. S. N. Murty, and Sarah B. Hall. "Characteristics of Internal Tides from ECCO Salinity Estimates and Observations in the Bay of Bengal." Remote Sensing 15, no. 14 (July 10, 2023): 3474. http://dx.doi.org/10.3390/rs15143474.
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Internal waves (IWs) are generated in all the oceans, and their amplitudes are large, especially in regions that receive a large amount of freshwater from nearby rivers, which promote highly stratified waters. When barotropic tides encounter regions of shallow bottom-topography, internal tides (known as IWs of the tidal period) are generated and propagated along the pycnocline due to halocline or thermocline. In the North Indian Ocean, the Bay of Bengal (BoB) and the Andaman Sea receive a large volume of freshwater from major rivers and net precipitation during the summer monsoon. This study addresses the characteristics of internal tides in the BoB and Andaman Sea using NASA’s Estimating the Circulation and Climate of the Ocean (ECCO) project’s high-resolution (1/48° and hourly) salinity estimates at 1 m depth (hereafter written as ECCO salinity) during September 2011–October 2012, time series of temperature, and salinity profiles from moored buoys. A comparison is made between ECCO salinity and NASA’s Soil Moisture Active Passive (SMAP) salinity and Aquarius salinity. The time series of ECCO salinity and observed salinity are subjected to bandpass filtering with an 11–14 h period and 22–26 h period to detect and estimate the characteristics of semi-diurnal and diurnal period internal tides. Our analysis reveals that the ECCO salinity captured well the surface imprints of diurnal period internal tide propagating through shallow pycnocline (~50 m depth) due to halocline, and the latter suppresses the impact of semi-diurnal period internal tide propagating at thermocline (~100 m depth) reaching the sea surface. The semi-diurnal (diurnal) period internal tides have their wavelengths and phase speeds increased (decreased) from the central Andaman Sea to the Sri Lanka coast. Propagation of diurnal period internal tide is dominant in the northern BoB and northern Andaman Sea.
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Lerczak, James A., W. Rockwell Geyer, and Robert J. Chant. "Mechanisms Driving the Time-Dependent Salt Flux in a Partially Stratified Estuary*." Journal of Physical Oceanography 36, no. 12 (December 1, 2006): 2296–311. http://dx.doi.org/10.1175/jpo2959.1.
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Abstract The subtidal salt balance and the mechanisms driving the downgradient salt flux in the Hudson River estuary are investigated using measurements from a cross-channel mooring array of current meters, temperature and conductivity sensors, and cross-channel and along-estuary shipboard surveys obtained during the spring of 2002. Steady (subtidal) vertical shear dispersion, resulting from the estuarine exchange flow, was the dominant mechanism driving the downgradient salt flux, and varied by over an order of magnitude over the spring–neap cycle, with maximum values during neap tides and minimum values during spring tides. Corresponding longitudinal dispersion rates were as big as 2500 m2 s−1 during neap tides. The salinity intrusion was not in a steady balance during the study period. During spring tides, the oceanward advective salt flux resulting from the net outflow balanced the time rate of change of salt content landward of the study site, and salt was flushed out of the estuary. During neap tides, the landward steady shear dispersion salt flux exceeded the oceanward advective salt flux, and salt entered the estuary. Factor-of-4 variations in the salt content occurred at the spring–neap time scale and at the time scale of variations in the net outflow. On average, the salt flux resulting from tidal correlations between currents and salinity (tidal oscillatory salt flux) was an order of magnitude smaller than that resulting from steady shear dispersion. During neap tides, this flux was minimal (or slightly countergradient) and was due to correlations between tidal currents and vertical excursions of the halocline. During spring tides, the tidal oscillatory salt flux was driven primarily by oscillatory shear dispersion, with an associated longitudinal dispersion rate of about 130 m2 s−1.
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Terquem, Caroline. "On a new formulation for energy transfer between convection and fast tides with application to giant planets and solar type stars." Monthly Notices of the Royal Astronomical Society 503, no. 4 (January 28, 2021): 5789–806. http://dx.doi.org/10.1093/mnras/stab224.
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ABSTRACT All the studies of the interaction between tides and a convective flow assume that the large-scale tides can be described as a mean shear flow that is damped by small-scale fluctuating convective eddies. The convective Reynolds stress is calculated using mixing length theory, accounting for a sharp suppression of dissipation when the turnover time-scale is larger than the tidal period. This yields tidal dissipation rates several orders of magnitude too small to account for the circularization periods of late-type binaries or the tidal dissipation factor of giant planets. Here, we argue that the above description is inconsistent, because fluctuations and mean flow should be identified based on the time-scale, not on the spatial scale, on which they vary. Therefore, the standard picture should be reversed, with the fluctuations being the tidal oscillations and the mean shear flow provided by the largest convective eddies. We assume that energy is locally transferred from the tides to the convective flow. Using this assumption, we obtain values for the tidal Q factor of Jupiter and Saturn and for the circularization periods of pre-main-sequence binaries in good agreement with observations. The time-scales obtained with the equilibrium tide approximation are however still 40 times too large to account for the circularization periods of late-type binaries. For these systems, shear in the tachocline or at the base of the convective zone may be the main cause of tidal dissipation.
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van Caspel, Willem E., Patrick J. Espy, Robert E. Hibbins, and John P. McCormack. "Migrating tide climatologies measured by a high-latitude array of SuperDARN HF radars." Annales Geophysicae 38, no. 6 (December 21, 2020): 1257–65. http://dx.doi.org/10.5194/angeo-38-1257-2020.
Full textAbstract:
Abstract. This study uses hourly meteor wind measurements from a longitudinal array of 10 high-latitude SuperDARN high-frequency (HF) radars to isolate the migrating diurnal, semidiurnal, and terdiurnal tides at mesosphere–lower-thermosphere (MLT) altitudes. The planetary-scale array of radars covers 180∘ of longitude, with 8 out of 10 radars being in near-continuous operation since the year 2000. Time series spanning 16 years of tidal amplitudes and phases in both zonal and meridional wind are presented, along with their respective annual climatologies. The method to isolate the migrating tides from SuperDARN meteor winds is validated using 2 years of winds from a high-altitude meteorological analysis system. The validation steps demonstrate that, given the geographical spread of the radar stations, the derived tidal modes are most closely representative of the migrating tides at 60∘ N. Some of the main characteristics of the observed migrating tides are that the semidiurnal tide shows sharp phase jumps around the equinoxes and peak amplitudes during early fall and that the terdiurnal tide shows a pronounced secondary amplitude peak around day of year (DOY) 265. In addition, the diurnal tide is found to show a bi-modal circular polarization phase relation between summer and winter.