M2 Components Research Articles

A 3D Numerical Study on the Tidal Asymmetry, Residual Circulation and Saline Intrusion in the Gironde Estuary (France)

A full 3D numerical model is used for studying tidal asymmetry, estuarine circulation, and saline intrusion in the Gironde estuary. The model is calibrated and verified using the data measured during two field surveys in the Gironde estuary. Harmonic analysis of numerical results is proposed to understand how the superposition of M2, M4 and M6 components generate a complex estuarine circulation and salinity intrusion in the Gironde estuary. The numerical results show that the M6 component plays a significant role as important as the M4 one in modifying the nature of tidal asymmetry, especially in the Gironde upper estuary. In this case, the use of the phase lag between M2 and M4, neglecting M6, to predict the tidal asymmetry nature could produce errors. The effect of asymmetrical tides on saline intrusion and residual circulation is specifically discussed here.

Contrast of fine sediment dynamics between shoals and channels in a microtidal estuary with mixed semi-diurnal tides

Estuaries usually feature complex bathymetries, where shoals and channels are co-existent. Due to the differences in water depth, current, density gradient and therefore stratification, sediment dynamics on the shoal and in the channel demonstrate significant variations. In this study, field measurements were carried out during spring and neap tides in both wet and dry seasons in the Huangmaohai Estuary, a microtidal estuary located in the southwest of the Pearl River Delta. Harmonic analysis was conducted for the timeseries data of current and suspended sediment concentration (SSC) for each deployment. Sediment transport flux was decomposed into an advective component, and tidal pumping fluxes by different tidal constituents. During the neap tides, sediment transport is primarily controlled by the advective flux, whereas during the spring tides, tidal pumping fluxes become comparable to, sometimes even exceeding, the advective one. For a 25-hr period, the M1 component of SSC usually denotes the maximum SSC associated with the highest bottom stress, while the M2 component signifies the two highs of the SSC. The M4 component is generally insignificant. The M1 and M2 components can be induced by both the advection and bottom resuspension. For the resuspension part, the M1 component is mostly induced by tidal velocity asymmetry, while the M2 component is generated by tidal straining effect. Sediment transport at the shoal is mostly controlled by the advective flux and the tidal pumping due to tidal velocity asymmetry, while that in the channel is dictated by advective transport and the tidal pumping due to tidal mixing asymmetry.

Accuracy Assessment of Recent Global Ocean Tide Models Using Tide Gauge Measurements from the East Sea of Korea

Lee, J.-C. and Lee, D-H., 2023. Accuracy assessment of recent global ocean tide models using tide gauge measurements from the East Sea of Korea. Journal of Coastal Research, 39(2), 354–359. Charlotte (North Carolina), ISSN 0749-0208. The continued rise in average sea level owing to climate change has intensified coastal damage worldwide. Therefore, various studies in the field of oceanography and hydrography including the development of ocean tidal prediction models are in progress. In this study, the accuracy of the recent ocean tide models using the long and short-term tide gauge measurements from seven tidal gauging stations and 10 tidal benchmarks at the coastal area in the East Sea of Korea was assessed. For this purpose, a total of five ocean tide models, DTU10, FES2014, OSU12, NAO99, and TPXO9 were used. The accuracy of the four major tidal components (M2, S2, K1, and O1) were assessed based on the same components determined from direct tide gauge measurements in east coastal area of Korea. The tide gauge measurements used in this study consisted of long-term observation data of over 1.7 years on average from seven permanent tide gauge stations and short-term observation data of about 6.6 months on average from 10 tidal benchmarks. Observation and determination of tidal components were performed by the Korea Hydrographic and Oceanographic Agency. The accuracy of each ocean tide model was assessed by comparing the amplitude of four major components with those from tide gauge measurements for each location of tide gauge. The lowest accuracy of modelled component values was detected in the M2, S2, K1, and O1 tidal components of NAO99 model. On the contrary, FES2014 was the most accurate in M2, S2 tidal components and TPXO9 was most accurate in the K1, O1 tidal components in the East Sea of Korea.

Comparison of Admiralty and Least Square Methods for Tidal Analysis in Mandangin Island, Sampang Regency, East Java

The existence of hydro-oceanographic information such as tides plays an essential role in supporting coastal areas' transportation. This study aims to compare the tidal analysis results in Mandangin Island, Sampang Regency, East Java using the Admiralty and Least Square methods. The data used in this study are tidal data for May and November 2020, which represent the dry and rainy seasons in Indonesia. Tide data are obtained from the Geospatial Information Agency (BIG) at one-hour intervals. From this research, it can be concluded that the tidal types generated from the Admiralty and Least Square methods in Mandangin Island, East Java, are mixed types with semidiurnal tendencies. The use of the Admiralty and Least Square methods results in the difference in the harmonic components' amplitude values. The M2 and O1 components have an enormous difference in May 2020, with amplitude values of 0.0003 and 0.0002, and the difference in the amplitude values of the harmonic components also occurred in November 2020. The M2 component has the most significant difference compar e to other components, namely 0.0011. The components O1, P1, and MS4 in the same month result in a relatively small difference in amplitude values with values of 0.0002, 0.0002, and 0.0001. For further tidal research, data corrections should be considered, a nodal correction to produce more accurate observational data. This correction can use the T_Tide program with constants obtained from the analysis process.

Tribological behaviour of uncoated steel and fluorocarbon coated steel under dry and lubricated sliding conditions

Due to positive tribological performance, fluorocarbon coatings have established an importance in many applications, as a possible replacement to enhancement and substitute traditional liquid lubricants. The literature in this area is to a certain extent limited, especially on the Tribological behaviour of fluorocarbon coated and fluorocarbon uncoated components in aggressive conditions. In this work, fluorocarbon coated on HSS M2 and fluorocarbon uncoated components friction and wear along with this it also gives smooth and noise free running operation. Long-term durability experiments also showed the superiority and suitability of fluorocarbon coating for potential use in many applications. Fluorocarbon coatings are considered for their advantageous mixture of properties, in specific it has exceptional low friction as well as release capability and good chemical properties. As a result of experimentations, fluorocarbon coating shows the coefficient of friction as low as 0.196 which is much better than many other coatings in the fluorocarbon category and wear rate is also way better which is 1.0610×10-5mm3/Nm.

Morphodynamic Characteristics and Medium-Term Simulation of the North—South Passage Under the Impact of the Yangtze Estuary Deepwater Navigation Channel Project

The morphological evolution characteristics of the North—South Passage area since the construction of the Yangtze Estuary Deepwater Navigation Channel Project (DNCP) are analyzed on the basis of the measured data. A two-dimensional morphodynamics numerical model of the Yangtze Estuary is established to verify the morphological evolution of the North—South Passage under the influence of the DNCP and to predict the future evolution in the next 40 years. Data analysis shows that the North Passage has experienced rapid adjustment stages and adaptive stages after the construction of the DNCP. Slow erosion occurred along the main channel, and slow siltation could be observed in the area between the groins. The South Passage showed a state of upper section erosion and down section deposition. At present, the whole South Passage is in a slight erosion state. According to the numerical model, the eroding and silting speed of the North Passage will slow down in the future. The present state that erosion occurs in the main channel and siltation occurs between the groins will continue. The South Passage will still maintain upper section erosion and down section deposition in the future. Due to the main channel erosion of the North Passage and siltation of the South Passage, the sediment division ratio of the North Passage will increase in the future but still be smaller than 50%. After morphological evolution of 40 years, the direction of residual sediment transport caused by M2 and M4 tidal components in the North Passage has not changed, but the transport rate will decrease. It is considered that the morphological evolution of the North—South Passage could reach a relatively stable state after 40 years.

Structural Characterization of Atomic Layer Deposited Vanadium Dioxide

Vanadium dioxide (VO2) is a promising smart material particularly appealing for added functionality in both electronic and optical applications. We investigate the structure of VO2 films fabricated using atomic layer deposition (ALD) on c-Al2O3 substrates and the structure of the same VO2 films after an optimized anneal for 2 h at 585 °C in 10–5 Torr O2. Synchrotron-based grazing incidence X-ray diffraction (GIXRD) measurements revealed that the as-deposited ALD VO2 contains small crystalline inclusions of both V2O5 and VO. Ex situ annealing of the ALD VO2 film results in formation of mixed phase VO2 (predominantly M1 with indications of a small amount of M2), with a twinned monoclinic structure that is highly oriented and lattice matched to the c-Al2O3 substrate. Using in situ temperature-dependent measurements, the M1 and M2 components were shown to transition across different temperature ranges, which could account for the hysteretic behavior seen in these VO2 thin films. Additionally, these high-quali...

Sea-level rise impacts on the tides of the European Shelf

Sea-level rise (SLR) can modify not only total water levels, but also tidal dynamics. Several studies have investigated the effects of SLR on the tides of the western European continental shelf (mainly the M2 component). We further investigate this issue using a modelling-based approach, considering uniform SLR scenarios from −0.25m to +10m above present-day sea level. Assuming that coastal defenses are constructed along present-day shorelines, the patterns of change in high tide levels (annual maximum water level) are spatially similar, regardless of the magnitude of sea-level rise (i.e., the sign of the change remains the same, regardless of the SLR scenario) over most of the area (70%). Notable increases in high tide levels occur especially in the northern Irish Sea, the southern part of the North Sea and the German Bight, and decreases occur mainly in the western English Channel. These changes are generally proportional to SLR, as long as SLR remains smaller than 2m. Depending on the location, they can account for +/−15% of regional SLR. High tide levels and the M2 component exhibit slightly different patterns. Analysis of the 12 largest tidal components highlights the need to take into account at least the M2, S2, N2, M4, MS4 and MN4 components when investigating the effects of SLR on tides. Changes in high tide levels are much less proportional to SLR when flooding is allowed, in particular in the German Bight. However, some areas (e.g., the English Channel) are not very sensitive to this option, meaning that the effects of SLR would be predictable in these areas, even if future coastal defense strategies are ignored. Physically, SLR-induced tidal changes result from the competition between reductions in bed friction damping, changes in resonance properties and increased reflection at the coast, i.e., local and non-local processes. A preliminary estimate of tidal changes by 2100 under a plausible non-uniform SLR scenario (using the RCP4.5 scenario) is provided. Though the changes display similar patterns, the high water levels appear to be sensitive to the non-uniformity of SLR.

High-resolution numerical modelling of the barotropic tides in the Gulf of Gabes, eastern Mediterranean Sea (Tunisia)

A high-resolution 2D barotropic tidal model was developed for the Gulf of Gabes and used to characterise hydrodynamic processes and tidal dynamics. The model is based on the Regional Ocean Modelling System. It is forced at the open boundaries by the semidiurnal M2 and S2 astronomical components while meteorological forcing has been neglected. The model results show good agreement with observations confirming that it reproduces the gulf's main tidal characteristics reasonably well. In fact, the simulated semidiurnal tidal components M2 and S2 generate important sea level variations and coastal currents. Tidal propagation is directed to the gulf's western sector while tidal resonance occurs in its inner sector where the M2 and S2 amplitudes are about 50 and 36 cm, respectively. Phase maxima (170°–185°) are located inside Boughrara Lagoon for both the simulated M2 and S2 tides. The strongest currents are found in shallow coastal regions and at the lagoon's western inlet. During spring tides, currents are around 10–20 cm s−1 in the gulf center and up to 50 cm s−1 inside the lagoon.

Analysis of high frequency geostationary ocean colour data using DINEOF

DINEOF (Data Interpolating Empirical Orthogonal Functions), a technique to reconstruct missing data, is applied to turbidity data obtained through the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board Meteosat Second Generation 2. The aim of this work is to assess if the tidal variability of the southern North Sea in 2008 can be accurately reproduced in the reconstructed dataset. Such high frequency data have not previously been analysed with DINEOF and present new challenges, like a strong tidal signal and long night-time gaps. An outlier detection approach that exploits the high temporal resolution (15 min) of the SEVIRI dataset is developed. After removal of outliers, the turbidity dataset is reconstructed with DINEOF. In situ Smartbuoy data are used to assess the accuracy of the reconstruction. Then, a series of tidal cycles are examined at various positions over the southern North Sea. These examples demonstrate the capability of DINEOF to reproduce tidal variability in the reconstructed dataset, and show the high temporal and spatial variability of turbidity in the southern North Sea. An analysis of the main harmonic constituents (annual cycle, daily cycle, M2 and S2 tidal components) is performed, to assess the contribution of each of these modes to the total variability of turbidity. The variability not explained by the harmonic fit, due to the natural processes and satellite processing errors as noise, is also assessed.

A numerical study on the circulation and tide in a zigzag bay

The Shacheng Bay (SCB) is one of the most complex coastal bays in southeast China and due to the fact of complicated geometry and dynamic coastal processes, it is considered as a challenging area for the numerical simulation of its hydrodynamic characteristics. The most advanced finite volume ocean model, finite-volume coastal ocean model (FVCOM), has adopted to simulate this hydrodynamic system, where tidal currents, tidal residual current and dye diffusion processes were studied and analyzed quantitatively. The validation of this numerical model matches well with various observation data, including elevation and current data. The misfit of a tidal elevation has a relative standard error of 3.66% and 4.67% for M2 and S2 tide components. The current validation shows a good match with an average error of 10 cm/s and 8° in the speed major axis and its direction respectively between the simulation and the measurement. This proves the robustness and reliability of this model. It is also found that the cape effect is significant and important in this system. The dye diffusion simulations show a 53 d flushing period for the whole inner bay waterbody. The results are of its first kind for understanding the hydrodynamic system in the SCB and they can provide helpful and trustful scientific information for others.

对每日和更短周期水头波动进行傅里叶分析来了解相互连接的地表水/地下水系统

The long-term monitoring records of hydraulic heads frequently contain fluctuations originating from different cyclic drivers. Fourier analysis applied to these records can reveal connected surface-water/groundwater system characteristics. The various components of the atmospheric tides, the earth tides and the presence of diurnal responses to evapotranspiration are identified and isolated through band-pass filtering of data recorded from both vented and absolute gauge transducers. The signature of the different cyclic drivers is contained in amplitude and phase of the various signal components and can be used to determine the degree of system confinement. A methodology is described for the calculation of barometric efficiency in confined aquifers based upon the amplitude of the M2 and S2 components of the earth and atmospheric tides. It is demonstrated that Fourier analysis of water-level fluctuations is a simple but underused tool that can help to characterise shallow groundwater systems.

서해 근소만-선유도 갯벌 퇴적층의 지온변화에 관한 연구

The vertical structure of sediment temperatures in the tidal flats of Geunso Bay and Seonyu Island in western Korea were measured for more than a year and analyzed. Mean temperature decreased with depth in spring and summer. On the contrary, it increased with depth in fall and winter, faithfully reflecting the seasonal variation resulting from the heating and cooling of the surface sediment. The surface sediment temperatures are shown to be strongly dependent on solar radiation, M2, and M4 tidal components. They are also weakly affected by precipitation. Thermal diffusivity of sediment is estimated at each depth and in each of the four seasons by applying the amplitude equation method. In Geunso Bay, the estimated seasonal-mean values decreased with depth, while they showed little change in Seonyu Island. Depth-averaged thermal diffusivity in Geunso Bay (<TEX>$1.94 {\times}10^{-7}m^2/s$</TEX>) was smaller than Seonyu Island (<TEX>$2.20 {\times}10^{-7}m^2/s$</TEX>). The variability of thermal diffusivity is shown to corelate with sediment composition and sorting from the grain-size analysis of intertidal sediments in Geunso Bay and Seonyu-do.

A Numerical Study of Salt Fluxes in Delaware Bay Estuary

AbstractThe results of a numerical study of Delaware Bay using the Regional Ocean Modeling System (ROMS) are presented. The simulations are run over a range of steady river inputs and used M2 and S2 tidal components to capture the spring–neap variability. Results provide a description of the spatial and temporal structure of the estuarine exchange flow and the salinity field, as well the along-channel salt flux in the estuary. The along-channel salt flux is decomposed into an advective term associated with the river flow, a steady shear dispersion Fe associated with the estuarine exchange flow, and a tidal oscillatory salt flux Ft. Time series of Fe and Ft show that both are larger during neap tide than during spring. This time variability of Ft, which is contrary to existing scalings, is caused by the lateral flows that bring velocity and salinity out of quadrature and the stronger stratification during neap tide, which causes Ft to be enhanced relative to spring tide. A fit for the salt intrusion length L with river discharge Q for a number of isohalines is performed. The functional dependences of L with Q are significantly weaker than Q−1/3 scaling. It is concluded that the response of the salt field with river discharge is due to the dependence of Fe and Ft with Q and the relative importance of Ft to the total upstream salt flux: as river discharge increases, Fe becomes the dominant mechanism. Once Fe dominates, the salt field stiffens because of a reduction of the vertical eddy viscosity with increasing Q.

Mean circulation and high-frequency flow amplification in the Sable Gully

The Sable Gully, a broad, shelf break submarine canyon approximately 40km east of Sable Island on the eastern Scotian Shelf, separates Banquereau and Sable Island Banks. Unique among canyons on the eastern Canadian continental shelf because of its depth, steep slopes and extension far onto the shelf, its ecological significance and increasing human pressures led to its designation in 2004 under Canada's Oceans Act as the first Marine Protected Area (MPA) in the Atlantic Region. To improve the state of knowledge of the Gully MPA, a multi-disciplinary field program was carried out in 2006–07; the physical oceanographic component consisted of the deployment (April 2006) and recovery (August 2007) of four current meter moorings and CTD surveys. Analysis of this 16-month mooring deployment demonstrates that the mean circulation above the canyon rim (~200m) is characterized by a southwestward flow that appears unaffected by the canyon topography. There is also some indication of the existence of an eddy at rim depth. Below 500m, the circulation is dominated by an upcanyon flow (of order 0.02ms−1) at the mooring array (halfway between the canyon head and mouth). The mean, 200m-bottom transport towards the head of the Gully was estimated as 35,500m3s−1, implying an upwelling velocity of 1.7×10−4ms−1 (14md−1) over the area. Results also show bottom-intensified tidal flows and non-linear constituents due to the interaction of K1, O1, M2 and S2 components along the thalweg of the canyon; the strong overtides and compound tides observed in the Gully make it unique among canyons. Further analyses provide evidence of enhanced mixing in the Gully (Kv~180×10−4m2s−1), which is approximately 20 times that observed on the adjoining Scotian Shelf. Total variance of the currents in the Gully is about 2.5 times greater than that observed on the nearby continental slope with an equivalent water depth.

An inter-comparison of tidal solutions computed with a range of unstructured grid models of the Irish and Celtic Sea Regions

Three finite element codes, namely TELEMAC, ADCIRC and QUODDY, are used to compute the spatial distributions of the M2, M4 and M6 components of the tide in the sea region off the west coast of Britain. This region is chosen because there is an accurate topographic dataset in the area and detailed open boundary M2 tidal forcing for driving the model. In addition, accurate solutions (based upon comparisons with extensive observations) using uniform grid finite difference models forced with these open boundary data exist for comparison purposes. By using boundary forcing, bottom topography and bottom drag coefficients identical to those used in an earlier finite difference model, there is no danger of comparing finite element solutions for “untuned unoptimised solutions” with those from a “tuned optimised solution”. In addition, by placing the open boundary in all finite element calculations at the same location as that used in a previous finite difference model and using the same M2 tidal boundary forcing and water depths, a like with like comparison of solutions derived with the various finite element models was possible. In addition, this open boundary was well removed from the shallow water region, namely the eastern Irish Sea where the higher harmonics were generated. Since these are not included in the open boundary, forcing their generation was determined by physical processes within the models. Consequently, an inter-comparison of these higher harmonics generated by the various finite element codes gives some indication of the degree of variability in the solution particularly in coastal regions from one finite element model to another. Initial calculations using high-resolution near-shore topography in the eastern Irish Sea and including “wetting and drying” showed that M2 tidal amplitudes and phases in the region computed with TELEMAC were in good agreement with observations. The ADCIRC code gave amplitudes about 30 cm lower and phases about 8° higher. For the M4 tide, in the eastern Irish Sea amplitudes computed with TELEMAC were about 4 cm higher than ADCIRC on average, with phase differences of order 5°. For the M6 component, amplitudes and phases showed significant small-scale variability in the eastern Irish Sea, and no clear bias between the models could be found. Although setting a minimum water depth of 5 m in the near-shore region, hence removing wetting and drying, reduced the small-scale variability in the models, the differences in M2 and M4 tide between models remained. For M6, a significant reduction in variability occurred in the eastern Irish Sea when a minimum 5-m water depth was specified. In this case, TELEMAC gave amplitudes that were 1 cm higher and phases 30° lower than ADCIRC on average. For QUODDY in the eastern Irish Sea, average M2 tidal amplitudes were about 10 cm higher and phase 8° higher than those computed with TELEMAC. For M4, amplitudes were approximately 2 cm higher with phases of order 15° higher in the northern part of the region and 15° lower in the southern part. For M6 in the north of the region, amplitudes were 2 cm higher and about 2 cm lower in the south. Very rapid M6 tidal-phase changes occurred in the near-shore regions. The lessons learned from this model inter-comparison study are summarised in the final section of the paper. In addition, the problems of performing a detailed model–model inter-comparison are discussed, as are the enormous difficulties of conducting a true model skill assessment that would require detailed measurements of tidal boundary forcing, near-shore topography and precise knowledge of bed types and bed forms. Such data are at present not available.

Spatial and temporal variations of the correlation coefficient between M2 and S2 earth tides components and earthquake occurrences for the intermediate-depth seismic activity zones

The correlations between seismic activities and tidal periodicities are investigated at three seismic zones: Vrancea (Romania), Bucaramanga (Colombia) and Hindu Kush (Afganistan). The epicenter of earthquake nests distribution is characterized by intermediate-depth. In this paper, we study the influences of the principal lunar and solar semidiurnal tidal components M2 and S2 on seismic activities. The tidal phase is determined by HiCum stacking method according to the earthquake occurrence time and location. The stacking function could be shifted in time and space domain which provides the possibility to evaluate the seismic activities and tidal periodicities at both. The tidal phase distribution was tested by two independent methods Schuster and Permutation. The null hypothesis between seismic activities and selected tidal periodicities is rejected when the statistical p-values obtained by the two tests reach less than 5% level. As a result of the shift stacking function in time axis, a systematic temporal pattern related to the decrease of the p-values seems to be preceding occurrence of the larger earthquakes. A “tidal tomography” map is obtained when stacking function is shifted in 3D geometry following the epicenters distribution.

On the modification of tides in shallow water regions by wind effects

The influence of non‐linear effects upon tides in shallow coastal regions, due to the presence of a significant storm surge is examined using a two‐dimensional model of the west coast of Britain. The model has an unstructured grid, designed to have a high resolution mesh in the near coastal region of the eastern Irish Sea, the area chosen as the focus of this study. The influence of tide‐surge interaction upon the M2, M4 and M6 components of the tide, due to surges produced by steady uniform wind stresses is examined in detail. Calculations show that in deep regions the tide is unaffected by the surge. However, in shallow coastal regions there is significant modification of tidal elevations and currents. This arises because of changes in bottom stress, and the non‐linear interaction term in the hydrodynamic equations. In addition the locations of regions that “wet and dry” are changed during the tidal cycle due to the influence of the surge. This gives rise to significant spatial variations and changes in magnitude of the tide and its higher harmonics depending upon wind stress direction and water depth. These results explain why tidal energy remains in the surge residual in shallow water when it is computed by de‐tiding the total signal using a tide only calculation; an effect often found in observed surge residuals.

Harmonic analysis of suspended particulate matter in the Menai Strait (UK)

An application of harmonic analysis is presented to estimate M2 and M4 tidal constituents of various suspended particulate matter (SPM) fractions in a marine ecosystem. The data were collected on two cruises in August and September 2004. In both sets of data there appeared to be clearly identifiable advection (i.e. semidiurnal increases in concentrations), resuspension (i.e. quarterdiurnal increases in concentrations), and flocculation (e.g. increases in median diameter at slack waters) signals. In most cases, the simulations on M2 and M4 components (estimated using harmonic analysis) explained a considerable proportion of variance (typical r 2 is 0.4–0.65). However, some of the variables examined (e.g. median diameter in deeper layers) could not be modelled satisfactorily using the method chosen. In August, the amplitude of the M4 component was invariably lower than of the M2 component, thus indicating that advection signal dominated the overall dynamics observed. In September, however, this pattern was reversed for small and medium-sized particle diameters, thus indicating that resuspension for this fractions was prevalent. Another remarkable difference between the two data sets is the considerable difference between the estimated advection phases, which were, in general (and variable depending on the specific fraction), approximately 8 and 5 h after LW in August and September, respectively. These differences might have been partly related to the differences in the exact sampling locations, seasonal changes between the two cruises, local processes in the Menai Strait, and/or preceding meteorological conditions. The results are discussed in terms of their importance for the Menai Strait biota.

Utilizing Spectral Analysis of Coastal Discharge Computed by a Numerical Model to Determine Boundary Influence

Abstract In the present study, a spectral analysis was applied to field data and a numerical model of southeastern Everglades and northeastern Florida Bay that involved computing and comparing the power spectrum of simulated and measured flows at the primary coastal outflow creek. Four dominant power frequencies, corresponding to the S1, S2, M2, and O1 tidal periods, were apparent in the measured outflows. The model seemed to reproduce the magnitudes of the S1 and S2 components better than those of the M2 and O1 components. To determine the cause of the relatively poor representation of the M2 and O1 components, we created a steady-base version of the model by setting the time-varying forcing functions—rainfall, evapotranspiration, wind, and inland and tidal boundary conditions—to averaged values. The steady-base model was then modified to produce multiple simulations with only one time-varying forcing function for each model run. These experimental simulations approximated the individual effects of each ...