Tidal Phenomena Research Articles

Simulations of the low‐latitude midnight temperature maximum

To investigate possible sources of the low‐latitude midnight temperature maximum (MTM), a series of simulations was made with the National Center for Atmospheric Research thermosphere/ionosphere/electrodynamic general circulation model (TIEGCM). The MTM is a tidal phenomenon and thus is ultimately due to the thermospheric tidal sources: in situ thermal excitation; ion‐neutralmomentum coupling; and the tidal waves arising in the lower atmosphere which penetrate the thermosphere. In the TIEGCM, the development of the MTM is due to the upward propagating semidiurnal tides. The model simulations suggest that the observed seasonal variation of the MTM, in which the MTM occurs earlier and more strongly in the local summer hemisphere, may be due to the interaction of the 2,2 and 2,3 modes: in summer, the two modes reinforce each other, and in winter they offset each other. This study further suggests that much of the variability observed in the MTM may be due to the variability in the upward propagating tides. The semidiurnal modal mix impinging on the lower thermosphere may vary on a day‐to‐day basis, depending on the background mean temperature and winds.

Assimilating ocean tide determined data into global tidal models

A data assimilation procedure, which has successfully been applied to fictive and realistic scenarios, is applied to a 1 °-model making use of an effective iterative method for the solution of the minimization problem. Two sets of ocean tide determined data are used for the purpose of assimilation, the more extensive one mainly comprising pelagic together with some coastal sea surface elevation data, and the other one consisting of loading gravity data. The computed O1 and M2 global tidal oscillation systems, namely the fields of tidal elevation and loading gravity, are compared with numerous additional pelagic and coastal elevation data and with a selected number of proper gravity data, respectively. The assimilation of the two sets of data leads to an enormous reduction of the errors of the model results in all oceans. Assimilating this altogether still restricted number of data, allows studying the generation of realistic tidal oscillation phenomena by individual data and comparing these data effects with those having been obtained by previous data assimilation experiments using a model with coarser grid spacing. The field of dynamical residuals resulting from data assimilation reflects the far reaching influence of the data, and it is shown that the spatially integrated work done by the residuals contributes to the in all reduced rate of dissipation in the tidal power balance.

AVALIAÇÃO CRÍTICA DAS CAUSAS DA ZONAÇÃO DOS ORGANISMOS BENTÔNICOS EM COSTÕES ROCHOSOS

Normal 0 21 false false false MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabela normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} A critical evaluation of the different zonation systems, and the factors that control the upper and lower limits of distribution of benthic organisms on rocky shores was made. The main zonation systems, the classic, Stephenson & Stephenson. Lewis and the Peres system, are described. It is suggested that the Lewis system with the Portuguese terminology presented by PAULA (1987) be used in papers published in Brazil. The old dogma that littoral zonation is simply a reflection of tidal phenomena, has been substituted by an equally erroneous concept that all can be explained by biotic factors. More than a factor, the zonation of the benthic organisms along the rocky shore, is the result of physical and biological interactions which establish precise limits of distribuition.

Tides as a periodically-correlated random process

The possibility and expediency of analysing tidal phenomena using methods from the theory of periodically-correlated random processes are discussed. The model for simulating these processes allows the cyclicity and stochasticity of tidal oscillations to be considered and the variability of the regular course of tidal waves to be assessed. The model essentially expands the bounds of the classical theory for tidal phenomena.

Stage‐Discharge Relationship in Tidal Rivers

In coastal rivers, the water level is greatly affected by the upstream movement of a tidal wave. The latter creates higher flood stages that enlarge the flood plain areas and increase potential damages. In such rivers, the water level is not solely a function of the flow discharge but rather a joint function of both the discharge and tidal phenomena. The interference of the tidal backwater with the normal flow of the river causes a disruption in the normal stage‐discharge relationship. This paper attempts at formulating a linear relation between tidal water level and river flow discharge that can be used for the predictions of water level in coastal rivers and estuaries. Numerical applications were performed on the St. John river (New Brunswick) and the St. Lawrence river (Québec) in Canada with satisfactory results.

Compact approximations to the bottom friction term, for the study of tides propagating in channels

Approximations to the bottom friction term Ku| u|/( H + Z), found in the equations of tidal hydrodynamics, are presented, taking fully into account its nonlinear character. In upstream regions where the current no longer reverses, the friction term becomes 2 Ku 0u 1/ H as a first approximation, u 0 being the steady current, u 1 the oscillatory contribution. A two-term approximation reproduces the quadratic variation of the current field in the friction term, in zones where the current reverses: this approximation suffices to predict and understand the peculiarities in the damping of the incoming tidal components, associated with quadratic friction. It also helps identify and evaluate the compound harmonics which result from their nonlinear frictional interactions. three-term approximation should be applied when numerical accuracy becomes necessary. The approximations described have already shown themselves most helpful in the understanding of the effects of quadratic friction in tidal phenomena.

Operation of irrigation system and water management in low lying paddy area with creek network

Characteristics of the operation and management of irrigation systems were analyzed in the low lying paddy area with creek networks. The irrigation system in Kubota district was chosen as a suitable example for analyzing. The water use in the irrigation system is characterized by reuse of return flow from paddy fields to creeks utilizing those water storage functions. There is a time delay between the input water and run off in the creek network irrigation system. The complex tank model was, therefore, applied to analyze the system operation. It is clarified that the response of actual operation of the irrigation system due to rainfall depends on the drainage conditions affected by tidal phenomena of each block.

Is our environment stratified?

In a previous paper, we have shown that the external HI regions of galaxies allow for the determination of a direction of parallelism. Being correlated with the supercluster flattering, this direction hints at a stratification. We illustrate the possible role of such a stratification in warping and tidal phenomena of galaxies. This stratification seems to involve various types of objects, and might extend much beyond z = 0.1.

Numerical simulations of accretion discs – I. Superhumps: a tidal phenomenon of accretion discs

Numerical simulations of the SU UMa star Z Cha in outburst are presented which demonstrate the role of the secondary's tidal influence upon the accretion flow and provide explanations for the superhumps seen in SU UMa stars. They show that for a system with an extreme mass-ratio q=0.15, the disc is tidally unstable and can become asymmetric and slowly rotate in the inertial frame of reference. The tidal stresses raised in this disc by the secondary produce a peak in the light curve of order 30 per cent which recurs with a period 3.5 per cent longer than that of the orbit. This is interpreted as the superhump. Analytic considerations show that only for systems with mass-ratios more extreme than approximately 4 :: 1 will such behaviour occur, which is consistent with the known mass-ratio of SU UMa stars and other cataclysmic variables. Arguments based on the observed occurrence of superhumps in SU UMa stars are advanced which suggest that outbursts are periods of high disc viscosity whereas in quiescence the disc is in a low-viscosity state. This supports the general predictions of disc-instability models over mass-transfer driven bursts. It is, however, found to be likely that mass-transfer is high during the superoutburst of SU UMa stars.

Estimating Harmonic Parameters for Damped Co‐Oscillating Tides

The parameters of Ippen and Harleman's harmonic analysis for the study of long periodic waves are investigated with emphasis on semidiurnal tidal co‐oscillations in one‐dimensional open channels. The data required for application of this analysis are obtained through a numerical simulation of tidal propagation phenomenon by a finite element technique. From the characteristic quantities of the method, the wave‐number, k, and the dimensionless parameter, ϕ, are examined and then related analytically to a number of physical and geometrical quantities, including the bottom friction coefficient and dimensionless combinations of the wave amplitude, length and depth of the channel, and tidal wave length. Subsequently, qualitative and quantitative information is provided for the linearized friction factor M of Telegrapher's equation, the phase shift α between tidal heights and currents, and the damping modulus μ. The results are verified by experimental and field data.

Spatial aggregations of the swarming jellyfish Pelagia noctiluca (Scyphozoa)

In the Adriatic Sea, the spatial distribution and aggregation aspects of swarning Pelagia noctiluca (Forskal, 1775) were studied by SCUBA divers from August 1984 to November 1985. Medusae were asually distributed in the upper 20- to 30-m layer. Dense aggregations caused by wind, currents and tidal phenomena occurred only in shallow coastal waters. Maximum population densities of swarms drifting freely near the shore were estimated at about 20 individuals per cubic meter, but when they had drifted ashore jellyfish could reach concentrations of 150 to 600 individuals in the same volume of sea water. Some peculiar forms of aggregations could be distinguished: couples, clusters, and surface and bottom aggregations. The effects of wind, currents and geomorphological features of the shore on passive aggregations of jellyfish are presented.

Nutrient conditions in the Euboikos Gulf (west Aegean)

The Euboikos Gulf is a restricted embayment on the eastern coast of Greece, having a significant, unusual tidal phenomenon, and receiving some industrial and domestic wates. The South Euboikos Gulf has only slightly greater concentrations of nutrients than background, while the North Euboikos Gulf tends to accumulate nutrients, in particular nitrate and silicate. Also a comparison is made with the nutrient concentrations in polluted coastal gulfs of the Aegean. The different nutrient levels are due to the different sources of nutrients, as well as the morphology of each area and the circulation of the waters.

Absence of a tidal component in the diel pattern of locomotory activity of sea catfish,Arius felis

Sea catfish, tested individually for 3-day periods in an automated data acquisition system, displayed a nocturnal pattern of locomotor activity with 62% of the activity occurring during scotophase. In addition, there were two relative maxima of activity at 0700–0900 and 1300–1500 C.S.T. This diel pattern of activity could not be correlated with tidal phenomena in the fish's natural environment and is virtually identical to that exhibited by several freshwater catfish species. Thus, even though sea catfish are a primarily estuarine fish and subject to daily tidal fluctuations, tidal rhythmicity is apparently not used as a cue for diel activity patterns.

William Whewell and John Stuart Mill on the methodology of political economy

Primarily between 1833 and 1840, William Whewell attempted to accomplish what natural philosophers and scientists since at least Galileo had failed to do: to provide a systematic and broad-ranged study of the tides and to attempt to establish a general scientific theory of tidal phenomena. I document the close interaction between Whewell’s philosophy of science (especially his methodological views) and his scientific practice as a tidologist. I claim that the intertwinement between Whewell’s methodology and his tidology is more fundamental than has hitherto been documented.

Atlas of ocean tidal charts and maps, Part I: The semidiurnal principal lunar tide M2

Abstract In this paper the author presents the NSWC ocean tide model of the semidiurnal principal lunar (M2) tide in an atlas of ocean tidal charts and maps. The model is the computer result of a unique combination of mathematical and empirical techniques, which was introduced, extensively tested, and evaluated by Schwiderski (1978a, 1980a, b, 1983e). The computed M2 amplitudes and phases are tabulated along with all specially labeled empirical input data on a 1° × 1 ° grid system in 42° × 71° overlapping charts covering the whole oceanic globe. Corresponding global and arctic corange and cotidal maps are included to provide a quick overview of the major tidal phenomena. Significant qualitative and quantitative features are explained and discussed for proper application. In particular, the charted harmonic constants may be used to compute instantaneous M2 ocean tides with an accuracy of better than 5 cm any time and anywhere in the open oceans. Limitations of this accuracy in coastal waters and border sea...

Trace metals in a tidal Mediterranean embayment

The Euvoikos gulf, and the strait of Euripos therein, is a restricted embayment on the eastern coast of Greece having a significant, unusual tidal phenomenon and receiving some domestic, trade and industrial wastes from the town of Chalkis and several coastal industries. The purpose of the present work was to study the influence of the tidal current and the anthropogenic inputs on the distributions of several trace elements (namely, Pb, Cu, Zn, Cr, Fe, Mn and Ni) in the seawaters (as dissolved and particulate species) and the sea-bottom sediments. Thorough mixing, resuspension and transport of fine particles and direct discharges are the major mechanisms affecting the distribution patterns.

Evidence for 18.6 year MN signal in temperature and drought conditions in North America since AD 1800

Evidence for the 18.6 year lunar nodal MN term in air temperature is found at 30 stations in eastern North America. Since AD 1800 the mean discrepancy in epoch between maxima in temperature and maxima in the Drought Area Index (DAI) for the western United States vis‐a‐vis, the maxima in the MN tide is 0.9 and 0.1 yr, respectively. Also, a cluster of 9 stations in western Canada yields the 18.6 yr term which is out of phase with stations in eastern North America and is indicative of a standing tidal wave in the atmosphere. This suggests that enhanced drought conditions in the western United States are neither ‘recurrent’ nor ‘rhythmic’ on a time scale of 20 yr, but rather periodic with a period of 18.6 yr. Finally, the Rocky Mountain system is seen as an influence for atmospheric tidal phenomena at epochs of maximum in the MN tide as well as for maxima in the temperature records and the DAI.

Tidal phenomena and migration, production, and distribution of hydrocarbon pools

New problems in the migration of fluids and in the formation and distribution of hydrocarbon pools in relation to tidal phenomena are discussed in the context A.R. Kinzikeyev's paper, Effects of Earth Tides as a Factor in the Migration, Formation, and Distribution of Hydrocarbon Pools, Geologiya Nefti i Gaza, 1978, no. 5, 36-39. (JMT)

The Earth's rotation and atmospheric circulation, from 1963 to 1973

Summary. The zonal angular momentum of the atmospheric circulation has been evaluated month-by-month and compared with astronomical observations of the length-of-day for the 10 years from 1963 May to 1973 April. The reason for undertaking this study is to enable the astronomical observations to be ‘corrected’ for the zonal wind effect and to investigate the residual excitation function for solid-Earth contributions. The principal conclusions reached are the following: (i) The annual change in length-of-day is almost entirely due to the seasonal changes in the zonal circulation with tidal, oceanographic and hydrologic phenomena contributing together at most 10 per cent of the total excitation, (ii) The semi-annual term is predominantly due to the zonal wind and the body tide, with oceanic and hydrologic terms contributing about 10 per cent, (iii) The atmospheric circulation plays a dominant role in length-of-day changes in the period range from 1 to about 4 yr. This is partly associated with the quasi-biennial oscillation and its harmonics. Both the period and amplitude of these fluctuations are very variable, (iv) At longer periods the atmosphere may still contribute to the total excitation but other excitation functions begin to rise above the spectrum of the meteorological excitation, (v) At periods less than about 1 yr the atmospheric excitation is dominant, and while the presence of other excitation functions cannot be excluded, they cannot exceed 20 per cent of the wind excitation. On the basis of these results the astronomical record from 1962 to 1978 has been ‘corrected’ for the meteorological ‘noise’. The residual excitation exhibits only fluctuations on a time-scale of about 5 yr and longer and it is this result that must be attributed to core-mantle interactions or to other solid-Earth excitation functions.

Motion of a visco-elastic sphere in a central newtonian force field

Approximate equations are obtained, describing the evolution of translational-rotational motion of a visco-elastic sphere in a central Newtonian force field,its steady-state motions are found, and their stability is investigated. The motion described can serve as one model of tidal phenomena under the motion of a planet of the solar system /1/. It has been shown previously /2/ that in the presence of energy dissipation a deformable planet tends towards a steady-state rotation around the attracting center, under which the planet's center of mass describes a circle, while its orientation in the orbital axes in unchanged.