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L. V. Cherkesov - One of the best experts on this subject based on the ideXlab platform.
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generation of internal waves by a Barotropic Tide in the coastal zone
Physical Oceanography, 2000Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:Within the framework of the linear theory of long waves, we study internal waves generated by a Barotropic Tide in a two-layer ocean of variable depth taking into account the influence of the Coriolis force. Barotropic waves run over an extended unevenness of the bottom at an arbitrary angle. This unevenness is regarded as a model of the continental slope and shelf. We establish the dependences of the amplitudes of generated internal waves on the angle of incidence of the Barotropic Tide, topography of the bottom, and stratification.
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the influence of stratification on the field of wave disturbances generated by a Barotropic Tide in the vicinity of the mid atlantic ridge
Physical Oceanography, 1997Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:In the framework of the linear theory for the long waves occurring in a fluid with a density gradient, the paper concentrates on the field of wave disturbances generated by a Barotropic Tide in the vicinity of the Mid-Atlantic ridge. Dependences of the wave amplitudes and velocities on the stratification parameters, the angle of onrunning and the period of the Barotropic Tide have been obtained. A similar study for a model ridge relief of paraboloidal shape has been conducted in ref. 1.
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The effect of currents on the generation of internal waves by a Barotropic Tide near an underwater ridge
Physical Oceanography, 1997Co-Authors: E. M. Kolomoitseva, L. V. CherkesovAbstract:In the frame of the linear theory for long waves, the paper studies long waves generated by a Barotropic Tide running at an arbitrary angle over a bottom ridge. The ocean is assumed to be two-layered. In the area of a ridge with a rectangular cross section, geostrophic flows are considered, coupled with the inclinations of the free surface and interface. Wave amplitudes are shown to depend on the angle of an onrunning Tide and this allows us to reach a conclusion about the influence of a geostrophic current on the generation of internal waves.
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The generation of non-linear internal waves by a Barotropic Tide in the area of a solitary bottom elevation
Physical Oceanography, 1996Co-Authors: Vladislav V Fomin, L. V. CherkesovAbstract:A mathematical model is suggested for calculating current, density, and pressure fields in the area of a solitary bottom rise (seamount). The model is based on a set of non-linear differential equations governing the motion of an inviscid continuously stratified fluid. The algorithm for solving the equations is based on the splitting technique. The model has been used to compute non-linear baroclinic waves generated by a Barotropic Tide in the seamount area.
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generation of internal waves by a semidiurnal Barotropic Tide in the mid atlantic ridge area
Physical Oceanography, 1996Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:Internal waves occurring in the specific Mid-Atlantic ridge area as a result of the impinging of a Barotropic Tide are studied in the terms of the linear theory for surface waves. The ocean is assumed to be double-layered, with a tidal wave running onto it at an arbitrary angle. The dependences of the wave amplitudes and horizontal velocities on the angle of run-on of a tidal wave are derived. Similar studies for the model bottom topography have been reported in refs 1–3.
S. V. Dovgaya - One of the best experts on this subject based on the ideXlab platform.
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generation of internal waves by a Barotropic Tide in the coastal zone
Physical Oceanography, 2000Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:Within the framework of the linear theory of long waves, we study internal waves generated by a Barotropic Tide in a two-layer ocean of variable depth taking into account the influence of the Coriolis force. Barotropic waves run over an extended unevenness of the bottom at an arbitrary angle. This unevenness is regarded as a model of the continental slope and shelf. We establish the dependences of the amplitudes of generated internal waves on the angle of incidence of the Barotropic Tide, topography of the bottom, and stratification.
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the influence of stratification on the field of wave disturbances generated by a Barotropic Tide in the vicinity of the mid atlantic ridge
Physical Oceanography, 1997Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:In the framework of the linear theory for the long waves occurring in a fluid with a density gradient, the paper concentrates on the field of wave disturbances generated by a Barotropic Tide in the vicinity of the Mid-Atlantic ridge. Dependences of the wave amplitudes and velocities on the stratification parameters, the angle of onrunning and the period of the Barotropic Tide have been obtained. A similar study for a model ridge relief of paraboloidal shape has been conducted in ref. 1.
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generation of internal waves by a semidiurnal Barotropic Tide in the mid atlantic ridge area
Physical Oceanography, 1996Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:Internal waves occurring in the specific Mid-Atlantic ridge area as a result of the impinging of a Barotropic Tide are studied in the terms of the linear theory for surface waves. The ocean is assumed to be double-layered, with a tidal wave running onto it at an arbitrary angle. The dependences of the wave amplitudes and horizontal velocities on the angle of run-on of a tidal wave are derived. Similar studies for the model bottom topography have been reported in refs 1–3.
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Investigation of internal waves generated by a diurnal Barotropic Tide in the vicinity of an oceanic ridge
Physical Oceanography, 1994Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:Internal waves occurring near an oceanic ridge as a result of impingement of a Barotropic Tide are scrutinized in terms of the long theory for long waves. The ocean is assumed to be double-layered, the relief continuously changing, and the tidal wave on-running at an arbitrary angle. The dependences of the wave amplitudes and horizontal velocities on the ridge's latitude, the angle of Tide running, and the depth of the density jump layer are obtained. Similar investigations for the model bottom relief have been conducted in refs 1 and 3.
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The generation of internal waves by the diurnal Barotropic Tide in the area of extensive irregularity of the bottom topography
Physical Oceanography, 1993Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:The generation of internal waves by the Barotropic Tide in a two-layer ocean of variable depth is studied within the framework of the linear theory of long waves in view of the Coriolis force. A Barotropic wave climbs at an arbitrary angle to the axis of the extensive ridge with constantly varying profile. The relationships between the amplitudes of the generated internal waves, the location of the ridge, and the angle of climb of the Barotropic Tide are studied. The analogous research is given in refs 1 and 2.
Brian K Arbic - One of the best experts on this subject based on the ideXlab platform.
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optimizing internal wave drag in a forward Barotropic model with semidiurnal Tides
Ocean Modelling, 2015Co-Authors: Maarten C Buijsman, Brian K Arbic, Jay F Shriver, James G Richman, Patrick G Timko, J A M Green, Robert W Helber, Alan J WallcraftAbstract:A global tuning experiment for the semidiurnal Tide is performed with a Barotropic model. The model is forced with the M2 equilibrium Tide and accounts for the self-attraction and loading (SAL) term. In addition to a quadratic drag, various linear internal wave drag terms adjusted by a scale factor of Oð1Þ are applied. The drag terms include the original Nycander (2005) tensor scheme, the Nycander tensor scheme reduced at supercritical slopes, and their scalar sisters, a Nycander scalar scheme computed for additional abyssal hill roughness, and the Jayne and St. Laurent (2001) scalar scheme. The Nycander scheme does not have a tunable parameter, but to obtain the best tidal solutions, it is demonstrated that some tuning is unavoidable. It is shown that the scalar Nycander schemes yield slightly lower root-mean square (RMS) elevation errors vs. the data-assimilative TPXO Tide model than the tensor schemes. Although the simulation with the optimally tuned original Nycander scalar yields dissipation rates close to TPXO, the RMS error is among the highest. The RMS error is lowered for the reduced schemes, which place relatively more dissipation in deeper water. The inclusion of abyssal hill roughness improves the regional agreement with TPXO dissipation rates, without changing the RMS errors. It is difficult to have each ocean basin optimally tuned with the application of a constant scale factor. The relatively high RMS error in the Atlantic Ocean is reduced with a spatially varying scale factor with a larger value in the Atlantic. Our best global mean RMS error of 4.4 cm for areas deeper than 1000 m and equatorward of 66 is among the lowest obtained in a forward Barotropic Tide model.
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accuracy assessment of global Barotropic ocean Tide models
Reviews of Geophysics, 2014Co-Authors: Detlef Stammer, Richard D Ray, Ole Baltazar Andersen, Brian K Arbic, Wolfgang Bosch, Loren Carrere, Yongcun Cheng, Douglas S Chinn, Brian D DushawAbstract:The accuracy of state-of-the-art global Barotropic Tide models is assessed using bottom pressure data, coastal Tide gauges, satellite altimetry, various geodetic data on Antarctic ice shelves, and independent tracked satellite orbit perturbations. Tide models under review include empirical, purely hydrodynamic (“forward”), and assimilative dynamical, i.e., constrained by observations. Ten dominant tidal constituents in the diurnal, semidiurnal, and quarter-diurnal bands are considered. Since the last major model comparison project in 1997, models have improved markedly, especially in shallow-water regions and also in the deep ocean. The root-sum-square differences between Tide observations and the best models for eight major constituents are approximately 0.9, 5.0, and 6.5 cm for pelagic, shelf, and coastal conditions, respectively. Large intermodel discrepancies occur in high latitudes, but testing in those regions is impeded by the paucity of high-quality in situ Tide records. Long-wavelength components of models tested by analyzing satellite laser ranging measurements suggest that several models are comparably accurate for use in precise orbit determination, but analyses of GRACE intersatellite ranging data show that all models are still imperfect on basin and subbasin scales, especially near Antarctica. For the M2 constituent, errors in purely hydrodynamic models are now almost comparable to the 1980-era Schwiderski empirical solution, indicating marked advancement in dynamical modeling. Assessing model accuracy using tidal currents remains problematic owing to uncertainties in in situ current meter estimates and the inability to isolate the Barotropic mode. Velocity tests against both acoustic tomography and current meters do confirm that assimilative models perform better than purely hydrodynamic models.
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an evaluation of the Barotropic and internal Tides in a high resolution global ocean circulation model
Journal of Geophysical Research, 2012Co-Authors: Jay F Shriver, Richard D Ray, Brian K Arbic, James G Richman, E J Metzger, Alan J Wallcraft, Patrick G TimkoAbstract:[1] Global comparisons of Barotropic and internal Tides generated in an eddy-resolving ocean circulation model are made with tidal estimates obtained from altimetric sea surface heights and an altimetry-constrained Tide model. As far as we know, our Hybrid Coordinate Ocean Model (HYCOM) simulations shown here and in an earlier paper are the only published high-resolution global simulations to contain Barotropic Tides, internal Tides, the general circulation, and mesoscale eddies concurrently. Comparing the model Barotropic Tide with a global data-assimilative shallow water Tide model shows that the global tidal elevation differences are approximately evenly split between discrepancies in tidal amplitude and phase. Both the model and observations show strong generation of internal Tides at a limited number of “hot spot” regions with propagation of beams of energy for thousands of kilometers away from the sources. The model internal tidal amplitudes compare well with observations near these energetic tidal regions. Averaged over these regions, the model and observation internal Tide amplitude estimates agree to approximately 15% for the four largest semidiurnal constituents and 23% for the four largest diurnal constituents. Away from the hot spots, the comparison between the model and altimetric amplitude is not as good due, in part, to two problems, errors in the model Barotropic Tides and overestimation of the altimetric Tides in regions of strong mesoscale eddy activity. Examining the general energy distribution of the simulated internal Tide is an important first step in the evaluation of internal Tides in HYCOM.
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internal wave generation in a global baroclinic Tide model
Deep-sea Research Part Ii-topical Studies in Oceanography, 2004Co-Authors: Robert Hallberg, Harper L Simmons, Brian K ArbicAbstract:Abstract The energy flux out of Barotropic Tides and into internal waves (“conversion”) is computed using a global domain multi-layer numerical model. The solution is highly baroclinic and reveals a global field of internal waves radiating way from generation sites of rough topography. A small number of sites where intense internal wave generation occurs accounts for most of the globally integrated work done on the Barotropic Tide and dominates sites such as the Mid-Atlantic ridge. The globally integrated conversion of the M 2 Barotropic Tide is 891 Gigawatts and the globally integrated rate of working of the ocean by astronomical forcing is 2.94 Terawatts. Both of these estimates are close to accepted values derived from independent methods. Regional estimates of conversion are also similar to previous inferences, lending additional confidence that the solution has captured the essential physics of low-mode internal wave generation and that numerical prediction of conversion has skill in regions where no previous estimates are available.
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the accuracy of surface elevations in forward global Barotropic and baroclinic Tide models
Deep-sea Research Part Ii-topical Studies in Oceanography, 2004Co-Authors: Brian K Arbic, Harper L Simmons, Robert Hallberg, Stephen T GarnerAbstract:Abstract This paper examines the accuracy of surface elevations in a forward global numerical model of 10 tidal constituents. Both one-layer and two-layer simulations are performed. As far as the authors are aware, the two-layer simulations and the simulations in a companion paper (Deep-Sea Research II, 51 (2004) 3043) represent the first published global numerical solutions for baroclinic Tides. Self-consistent forward solutions for the global Tide are achieved with a convergent iteration procedure for the self-attraction and loading term. Energies are too large, and elevation accuracies are poor, unless substantial abyssal drag is present. Reasonably accurate tidal elevations can be obtained with a spatially uniform bulk drag c d or horizontal viscosity K H , but only if these are inordinately large. More plausible schemes concentrate drag over rough topography. The topographic drag scheme used here is based on an exact analytical solution for arbitrary small-amplitude terrain, and supplemented by dimensional analysis to account for drag due to flow-splitting and low-level turbulence as well as that due to breaking of radiating waves. The scheme is augmented by a multiplicative factor tuned to minimize elevation discrepancies with respect to the TOPEX/POSEIDON (T/P)-constrained GOT99.2 model. The multiplicative factor may account for undersampled small spatial scales in bathymetric datasets. An optimally tuned multi-constituent one-layer simulation has an RMS elevation discrepancy of 9.54 cm with respect to GOT99.2, in waters deeper than 1000 m and over latitudes covered by T/P (66 ∘ N to 66 ∘ S). The surface elevation discrepancy decreases to 8.90 cm (92 percent of the height variance captured) in the optimally tuned two-layer solution. The improvement in accuracy is not due to the direct surface elevation signature of internal Tides, which is of small amplitude, but to a shift in the Barotropic Tide induced by baroclinicity. Elevations are also more accurate in the two-layer model when pelagic Tide gauges are used as the benchmark, and when the T/P-constrained TPXO6.2 model is used as a benchmark in deep waters south of 66 ∘ S. For Antarctic diurnal Tides, the improvement in forward model elevation accuracy with baroclinicity is substantial. The optimal multiplicative factor in the two-layer case is nearly the same as in the one-layer case, against initial expectations that the explicit resolution of low-mode conversion would allow less parameterized drag. In the optimally tuned two-layer M 2 solution, local values of the ratio of temporally averaged squared upper layer speed to squared lower layer speed often exceed 10.
Brian D Dushaw - One of the best experts on this subject based on the ideXlab platform.
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accuracy assessment of global Barotropic ocean Tide models
Reviews of Geophysics, 2014Co-Authors: Detlef Stammer, Richard D Ray, Ole Baltazar Andersen, Brian K Arbic, Wolfgang Bosch, Loren Carrere, Yongcun Cheng, Douglas S Chinn, Brian D DushawAbstract:The accuracy of state-of-the-art global Barotropic Tide models is assessed using bottom pressure data, coastal Tide gauges, satellite altimetry, various geodetic data on Antarctic ice shelves, and independent tracked satellite orbit perturbations. Tide models under review include empirical, purely hydrodynamic (“forward”), and assimilative dynamical, i.e., constrained by observations. Ten dominant tidal constituents in the diurnal, semidiurnal, and quarter-diurnal bands are considered. Since the last major model comparison project in 1997, models have improved markedly, especially in shallow-water regions and also in the deep ocean. The root-sum-square differences between Tide observations and the best models for eight major constituents are approximately 0.9, 5.0, and 6.5 cm for pelagic, shelf, and coastal conditions, respectively. Large intermodel discrepancies occur in high latitudes, but testing in those regions is impeded by the paucity of high-quality in situ Tide records. Long-wavelength components of models tested by analyzing satellite laser ranging measurements suggest that several models are comparably accurate for use in precise orbit determination, but analyses of GRACE intersatellite ranging data show that all models are still imperfect on basin and subbasin scales, especially near Antarctica. For the M2 constituent, errors in purely hydrodynamic models are now almost comparable to the 1980-era Schwiderski empirical solution, indicating marked advancement in dynamical modeling. Assessing model accuracy using tidal currents remains problematic owing to uncertainties in in situ current meter estimates and the inability to isolate the Barotropic mode. Velocity tests against both acoustic tomography and current meters do confirm that assimilative models perform better than purely hydrodynamic models.
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mode 1 internal Tides in the western north atlantic ocean
Deep Sea Research Part I: Oceanographic Research Papers, 2006Co-Authors: Brian D DushawAbstract:Abstract Mode-1 internal Tides were observed the western North Atlantic using an ocean acoustic tomography array deployed in 1991–1992 centered on 25°N, 66°W. The pentagonal array, 700-km across, acted as an antenna for mode-1 internal-Tides. Coherent internal-Tide waves with O (1 m) displacements were observed traveling in several directions. Although the internal Tides of the region were relatively quiescent, they were essentially phase locked over the 200–300 day data record lengths. Both semidiurnal and diurnal internal waves were detected, with wavenumbers consistent with those calculated from hydrographic data. The M 2 internal-Tide energy flux was estimated to be about 70 W m −1 , suggesting that mode-1 waves radiate 0.2 GW of energy, with large uncertainty, from the Caribbean island chain at this frequency. A global tidal model (TPXO 5) suggested that 1–2 GW is lost from the M 2 Barotropic Tide over this region, but the precise value was uncertain because the complicated topography makes the calculation problematic. In any case, significant conversion of Barotropic to baroclinic tidal energy does not occur in the western North Atlantic basin. It is apparent, however, that mode-1 internal Tides have very weak decay and retain their coherence over great distances, so that ocean basins may be filled up with such waves. Observed diurnal amplitudes were an order of magnitude larger than expected. The amplitude and phase variations of the K 1 and O 1 constituents observed over the tomography array were consistent with the theoretical solutions for standing internal waves near their turning latitude. The energy densities of the resonant diurnal internal waves were roughly twice those of the Barotropic Tide at those frequencies.
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observation of Barotropic Tide relative vorticity in the northwest atlantic
Journal of the Acoustical Society of America, 1996Co-Authors: Brian D Dushaw, Bruce M Howe, Peter F Worcester, Bruce D Cornuelle, Kurt MetzgerAbstract:Time series of reciprocal ray travel times were obtained at 350‐, 410‐, and 670‐km ranges in the western North Atlantic during the 1991–1992 Acoustic Mid‐Ocean Dynamics Experiment (AMODE). Transmissions were recorded for approximately 300 days between six transceivers in a pentagonal array. Barotropic current along each of the 15 propagation paths is derived from the difference of reciprocal ray travel times, while ten independent estimates of areal‐averaged relative vorticity are found by integrating current around triangles in the pentagonal array. The estimated tidal currents are highly accurate, and tidal relative vorticity at the M2 frequency is detected. This vorticity is induced primarily by the stretching of vortex lines by tidal elevation. Harmonic constants (amplitude, phase) of M2 tidal vorticity are about (4–8±2×10−9 s−1, 270°−320° ±20°), while harmonic constants of about (2–3×10−9 s−1, 300°−340°) are predicted using the shallow‐water equations. The measured tidal harmonic constants are compar...
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Barotropic and baroclinic Tides in the central north pacific ocean determined from long range reciprocal acoustic transmissions
Journal of Physical Oceanography, 1995Co-Authors: Brian D Dushaw, Bruce M Howe, Peter F Worcester, Bruce D Cornuelle, Douglas S LutherAbstract:Abstract Travel times of reciprocal 1000-km range acoustic transmissions, determined from the 1987 Reciprocal Tomography Experiment, are used to study Barotropic tidal currents and a large-scale, coherent baroclinic Tide in the central North Pacific Ocean. The difference in reciprocal travel times determines the tidal currents, while the sum of reciprocal travel times determines the baroclinic Tide displacement of isotachs (or equivalently, isotherms). The Barotropic tidal current accounts for 90% of the observed differential travel time variance. The measured harmonic constants of the eight major tidal constituents of the Barotropic Tide and the constants determined from current meter measurements agree well with the empirical–numerical tidal models of Schwiderski and Cartwright et al. The amplitudes and phases of the first-mode baroclinic Tide determined from sum travel times agree with those determined from moored thermistors and current meters. The baroclinic tidal signals are consistent with a large-...
Harper L Simmons - One of the best experts on this subject based on the ideXlab platform.
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internal wave generation in a global baroclinic Tide model
Deep-sea Research Part Ii-topical Studies in Oceanography, 2004Co-Authors: Robert Hallberg, Harper L Simmons, Brian K ArbicAbstract:Abstract The energy flux out of Barotropic Tides and into internal waves (“conversion”) is computed using a global domain multi-layer numerical model. The solution is highly baroclinic and reveals a global field of internal waves radiating way from generation sites of rough topography. A small number of sites where intense internal wave generation occurs accounts for most of the globally integrated work done on the Barotropic Tide and dominates sites such as the Mid-Atlantic ridge. The globally integrated conversion of the M 2 Barotropic Tide is 891 Gigawatts and the globally integrated rate of working of the ocean by astronomical forcing is 2.94 Terawatts. Both of these estimates are close to accepted values derived from independent methods. Regional estimates of conversion are also similar to previous inferences, lending additional confidence that the solution has captured the essential physics of low-mode internal wave generation and that numerical prediction of conversion has skill in regions where no previous estimates are available.
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the accuracy of surface elevations in forward global Barotropic and baroclinic Tide models
Deep-sea Research Part Ii-topical Studies in Oceanography, 2004Co-Authors: Brian K Arbic, Harper L Simmons, Robert Hallberg, Stephen T GarnerAbstract:Abstract This paper examines the accuracy of surface elevations in a forward global numerical model of 10 tidal constituents. Both one-layer and two-layer simulations are performed. As far as the authors are aware, the two-layer simulations and the simulations in a companion paper (Deep-Sea Research II, 51 (2004) 3043) represent the first published global numerical solutions for baroclinic Tides. Self-consistent forward solutions for the global Tide are achieved with a convergent iteration procedure for the self-attraction and loading term. Energies are too large, and elevation accuracies are poor, unless substantial abyssal drag is present. Reasonably accurate tidal elevations can be obtained with a spatially uniform bulk drag c d or horizontal viscosity K H , but only if these are inordinately large. More plausible schemes concentrate drag over rough topography. The topographic drag scheme used here is based on an exact analytical solution for arbitrary small-amplitude terrain, and supplemented by dimensional analysis to account for drag due to flow-splitting and low-level turbulence as well as that due to breaking of radiating waves. The scheme is augmented by a multiplicative factor tuned to minimize elevation discrepancies with respect to the TOPEX/POSEIDON (T/P)-constrained GOT99.2 model. The multiplicative factor may account for undersampled small spatial scales in bathymetric datasets. An optimally tuned multi-constituent one-layer simulation has an RMS elevation discrepancy of 9.54 cm with respect to GOT99.2, in waters deeper than 1000 m and over latitudes covered by T/P (66 ∘ N to 66 ∘ S). The surface elevation discrepancy decreases to 8.90 cm (92 percent of the height variance captured) in the optimally tuned two-layer solution. The improvement in accuracy is not due to the direct surface elevation signature of internal Tides, which is of small amplitude, but to a shift in the Barotropic Tide induced by baroclinicity. Elevations are also more accurate in the two-layer model when pelagic Tide gauges are used as the benchmark, and when the T/P-constrained TPXO6.2 model is used as a benchmark in deep waters south of 66 ∘ S. For Antarctic diurnal Tides, the improvement in forward model elevation accuracy with baroclinicity is substantial. The optimal multiplicative factor in the two-layer case is nearly the same as in the one-layer case, against initial expectations that the explicit resolution of low-mode conversion would allow less parameterized drag. In the optimally tuned two-layer M 2 solution, local values of the ratio of temporally averaged squared upper layer speed to squared lower layer speed often exceed 10.