Programs for computing properties of coastal-trapped waves and wind-driven motions over the continental shelf and slope

Brink, Kenneth H.; Chapman, David C.

doi:10.1575/1912/5368

Cited by 67 publications

(78 citation statements)

References 9 publications

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“…As a first step, we will use ROMS outputs (cross‐shore topographic and stratification vertical profiles) to estimate the CTW modal structures along the southwestern American and African coasts from the Brink and Chapman () formulation (cf., section 4.1 for the modal structure). Then CTW multimode linear model parameters (phase speed, frictional, and wind projection coefficients) will be derived and twin LCM configurations of the SEP and SEA (cf., section 4.3) will be developed.…”

Section: Resultsmentioning

confidence: 99%

“…In order to compute the free CTW modal structures and CTW linear model parameters along the coasts of southwestern American and African continents, we applied a modified version of the Brink and Chapman () Coastal‐Trapped Wave programs which solve equation (2), using a technique based on resonance iteration approach (Brink, ; Wang & Mooers, ). For a given cross‐shore section, providing the cross‐shore topographic profile and the stratification vertical profile, they calculate the CTW mode structures (

F_{n} (|, x, z)

) as well as the associated phase speed (

c_{n}

).…”

Section: Coastal‐trapped Wave Decompositionmentioning

confidence: 99%

See 1 more Smart Citation

Subseasonal Coastal‐Trapped Wave Propagations in the Southeastern Pacific and Atlantic Oceans: 1. A New Approach to Estimate Wave Amplitude

et al. 2018

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The Humboldt and the Benguela upwelling systems are connected to the equatorial variability through the coastal waveguide, so that a large variance of the coastal sea level and current variability can be described as an infinite sum of orthonormal free Coastal‐Trapped Wave (CTW) modes. The objective of this study is to infer the CTW mode contributions to the coastal variability in both systems at subseasonal timescales (<120 days) from regional ocean circulation model simulations. We develop and validate twin regional model configurations of the southeastern Pacific and Atlantic Oceans. Cross‐shore spatial structures of the first four free CTW modes are then derived from model mean stratification and topography along the southwestern African and South American continents. We introduce and validate a new methodology to estimate the gravest CTW mode contributions to model pressure and alongshore current. Our formulation draws on the orthonormality of the CTW modal structures, and uses a simple projection of the coastal and bottom model pressure onto each CTW structure. Results give confidence in the ability of this modal decomposition methodology to disentangle CTW mode contributions from complex nonlinear coastal processes that control the coastal subseasonal variability. In both systems, it allows to successfully extract the gravest poleward propagating CTW modes with velocities close to the theoretical values and amplitudes consistent with the solutions of a simple multimode linear CTW model. Furthermore, results show that both systems exhibit relatively different CTW dynamics and forcings which are discussed in the companion paper (Illig et al., 2018).

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Section: Resultsmentioning

confidence: 99%

F_{n} (|, x, z)

) as well as the associated phase speed (

c_{n}

).…”

Section: Coastal‐trapped Wave Decompositionmentioning

confidence: 99%

Subseasonal Coastal‐Trapped Wave Propagations in the Southeastern Pacific and Atlantic Oceans: 1. A New Approach to Estimate Wave Amplitude

et al. 2018

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“…A decomposition of the ROMS subseasonal coastal variability into free CTW modes is performed following the new methodology developed and described in the companion paper (Illig et al, ). At all cross‐shore sections along the southwestern African and South American continents, every 1/12°, CTW modal structures of the first four free CTW modes are derived using ROMS mean (2000–2008) stratification and topography by applying the Brink and Chapman () Coastal‐Trapped Wave programs. Subseasonal model pressure anomalies are then projected onto these structures based on the modal structure orthonormal conditions (Brink, ).…”

Section: Model Configurations and Methodologiesmentioning

confidence: 99%

Subseasonal Coastal‐Trapped Wave Propagations in the Southeastern Pacific and Atlantic Oceans: 2. Wave Characteristics and Connection With the Equatorial Variability

2018

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The objective of this study is to compare the characteristics of the oceanic teleconnection with the linear equatorial dynamics of two upwelling systems along the southwestern South American and African continents at subseasonal time scales (<120 days). Altimetric data analysis shows that the coastal variability remains coherent with the equatorial signal until 27°S in the southeastern Pacific (SEP), while in the southeastern Atlantic (SEA) it fades out south of 12°S. To explain this striking difference, our methodology is based on the experimentation with twin regional model configurations of the SEP and SEA Oceans. The estimation of free Coastal‐Trapped Waves (CTWs) modal structures and associated contribution to coastal variability allows inferring and comparing the characteristics of each CTW mode in the two systems; namely, their forcings, amplitude, dissipation rate, and scattering. Results show that the Pacific subseasonal equatorial forcing is only 20% larger than in the Atlantic, but important differences in the relative contribution of each baroclinic mode are reported. The first baroclinic mode dominates the eastern equatorial Pacific variability, while in the eastern equatorial Atlantic, the second mode is the most energetic. This leads to a drastic increase in the dissipation and scattering of the remotely forced CTW in the SEA sector, compared to the coastal SEP. Concomitantly, south of 15°S, the subseasonal coastal wind stress forcing is substantially more energetic in the SEA and participates in breaking the link between the equatorial forcing and the coastal variability. Our results are consistent with the solutions of a simple multimode CTW model.

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“…To interpret the observed flow variability along the Peruvian coast in terms of CTW, the cross-shore-depth structure of 185 CTWs was determined by considering the linear, hydrostatic, inviscid, and Boussinesq approximated equations of motion on an f-plane using local bathymetry and stratification (Brink, 1982;1989;Illig et al, 2018a). For alongshore scales larger than cross-shore scales and horizontally uniform stratification, cross-shore-vertical mode structures (eigenfunctions) and corresponding phase velocities (eigenvalues) solutions can be obtained from the simplified set of equations by using a resonance iteration approach (Brink, 1982;Brink and Chapman, 1987). 190…”

Section: Theoretical Coastal Trapped Wave Structurementioning

confidence: 99%

Influence of intraseasonal eastern boundary circulation variability on hydrography and biogeochemistry off Peru

Lüdke¹,

Dengler²,

Sommer³

et al. 2019

Preprint

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The Peruvian Upwelling System is characterized by high primary productivity fuelled by the supply of nutrients in a highly dynamic boundary circulation. The intraseasonal evolution of the physical and biogeochemical properties is 10 analysed based on shipboard observations and remote sensing conducted between April and June 2017 off central Peru. The poleward transport in the subsurface Peru Chile Undercurrent was highly variable and strongly intensified between mid and end of May. This intensification was likely caused by a first baroclinic mode downwelling coastal trapped wave excited at the equator at about 95°W that propagated poleward along the South American coast. The intensified poleward flow shortens the time of water mass advection from the equatorial current system to the study site. The impact of the anomalous advection 15 is mostly noticed in the nitrogen cycle because during the shorter time needed for poleward advection less fixed nitrogen loss occurs within the waters. This causes a strong increase of nitrate concentrations and a decrease in the nitrogen deficit. These changes suggest that the advection caused by the coastal trapped wave supersedes the simultaneous effect of anomalous downwelling in terms of nutrient response.

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Programs for computing properties of coastal-trapped waves and wind-driven motions over the continental shelf and slope

Cited by 67 publications

References 9 publications

Subseasonal Coastal‐Trapped Wave Propagations in the Southeastern Pacific and Atlantic Oceans: 1. A New Approach to Estimate Wave Amplitude

Subseasonal Coastal‐Trapped Wave Propagations in the Southeastern Pacific and Atlantic Oceans: 1. A New Approach to Estimate Wave Amplitude

Subseasonal Coastal‐Trapped Wave Propagations in the Southeastern Pacific and Atlantic Oceans: 2. Wave Characteristics and Connection With the Equatorial Variability

Influence of intraseasonal eastern boundary circulation variability on hydrography and biogeochemistry off Peru

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