High-resolution bathymetry estimates via X-band marine radar: 1. beaches

Honegger, D.; Haller, Merrick C.; Holman, Robert A.

doi:10.1016/j.coastaleng.2019.03.003

Cited by 39 publications

(42 citation statements)

References 40 publications

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“…Moreover, notable velocity divergence can be observed at the lift‐off region (see the yellow strip in x = 5–10 m in Figure a), which is due to the head of the stationary density current at the bottom. Similar surface signatures have been observed in the X‐radar measurement during the flood tide condition at Mouth of Columbia River [ Honegger , ].…”

Section: Discussionsupporting

confidence: 74%

“…Through significantly improved remote sensing technology, researchers have become interested in understanding coherent structures in estuaries and their particular surface signatures [e.g., Chickadel et al ., ; Horner‐Devine et al ., ; Honegger , ]. For this purpose, it is highly desirable that typical nonhydrostatic surface‐following and terrain‐following (σ‐coordinate) coastal ocean models can be used to simulate coherent structures.…”

Section: Introductionmentioning

confidence: 98%

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On nonhydrostatic coastal model simulations of shear instabilities in a stratified shear flow at high Reynolds number

Zhou

Hsu

et al. 2017

JGR Oceans

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The nonhydrostatic surface and terrain‐following coastal model NHWAVE is utilized to simulate a continually forced stratified shear flow in a straight channel, which is a generic problem to test the existing nonhydrostatic coastal models' capability in resolving shear instabilities in the field scale. The resolved shear instabilities in the shear layer has a Reynolds number of about 1.4 × 106, which is comparable to field observed value. Using the standard Smagorinsky closure with a grid size close to the Ozmidov length scale, simulation results show that the resolved energy cascade exceeds 1 order of magnitude and the evolution and turbulent mixing characteristics are predicted well. Two different approaches are used to estimate the turbulent dissipation rate, namely using the resolved turbulent energy spectrum and the parameterized subgrid turbulent dissipation rate, and the predicted results provide the upper and lower bounds that encompass the measured values. Model results show significantly higher turbulence in braids of shear instabilities, which is similar to field observations while both the subgrid turbulent dissipation rate and resolved vorticity field can be used as surrogates for measured high acoustic backscatter signals. Simulation results also reveal that the surface velocity divergence/convergence is an effective identifier for the front of the density current and the shear instabilities. To guide future numerical studies in more realistic domains, an evaluation on the effects of different grid resolutions and subgrid viscosity on the resolved flow field and subgrid dissipation rate are discussed.

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Section: Discussionsupporting

confidence: 74%

Section: Introductionmentioning

confidence: 98%

On nonhydrostatic coastal model simulations of shear instabilities in a stratified shear flow at high Reynolds number

Zhou

Hsu

et al. 2017

JGR Oceans

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“…This study provides the first joint validation of shallow water shipboard MR bathymetry and near-surface current retrieval, whose accuracies are interdependent. The comparison between the MR and echo sounder depth measurements gave a root-mean-square error of 1.2 m (or 7% of the mean water depth) and correlation coefficient r 2 of 0.97, exceeding or matching the MR depth retrieval accuracies reported by Osler (2011) andHonegger et al (2019). Due to predominantly short waves (mean peak wave period of 6.8 s), the MR depth retrieval was limited to depths up to ∼40 m. The MR currents were compared against measurements from ∼500 surface drifters, deployed in the shallow (<100 m) waters of the Louisiana Bight, and a shipboard ADCP.…”

Section: Discussionmentioning

confidence: 69%

“…More recently, Honegger et al () applied the cBathy algorithm to stationary MR data from two coastal sites in North Carolina and Oregon, where they found root‐mean‐square errors of 0.49 and 0.35 m with biases of 0.26 and 0.11 m, respectively. Their root‐mean‐square errors are lower than the 1.18 m error reported here (for the MR‐echo sounder comparison), however, their measurements were limited to water depths from 0–10 m. Hence, relative to the mean depth, the errors reported here are approximately the same.…”

Section: Discussionmentioning

confidence: 99%

“…It was later popularized through the cBathy algorithm (Holman et al, 2013), which has been applied widely to optical video measurements (e.g., Bergsma et al, 2016;Rutten et al, 2017;Sembiring et al, 2014). Very recently, Honegger et al (2019) applied the cBathy algorithm to MR data from two coastal stations, demonstrating an accuracy that is comparable with that of optical video. Another category of bathymetry retrieval methods, well suited to areas with a large tidal range, but not discussed further here, uses MR imagery to create sequences of intertidal waterline maps (Bird et al, 2017;Takewaka, 2005).…”

Section: Introductionmentioning

confidence: 99%

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Marine X‐Band Radar Currents and Bathymetry: An Argument for a Wave Number‐Dependent Retrieval Method

et al. 2020

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This study evaluates shipboard marine X‐band radar (MR) near‐surface current and bathymetry measurements under shallow water conditions. The retrieval algorithm is based on the surface wave signal within three‐dimensional wave number frequency MR backscatter intensity variance spectra. The MR data were collected during a research cruise that investigated submesoscale processes and their impact on oil spill transport in the Louisiana Bight. The MR currents and bathymetry are validated using measurements from 500 GPS‐equipped surface drifters, a shipboard acoustic Doppler current profiler, and a shipboard single‐beam echo sounder. Earlier results from the same experiment but using a different set of sensors indicate strong upper ocean vertical current shear over a 3.5 hr period, despite only mild wind forcing. Here, the MR currents are derived as a function of wave number, providing a measure of vertical shear for the full duration of the cruise. Strong vertical shear is frequently observed, with a maximum difference of 0.42 m/s between the MR high (effective depth of ∼0.9 m) and low ( ∼2.4 m) wave number bins. Treating the drifter and echo sounder measurements as truth, the accuracies of the MR near‐surface currents and bathymetry are 0.04–0.07 m/s and 1.2 m (or 7% of the mean water depth). However, it is shown that ∼50% of the MR high wave number and drifter current differences is due to vertical shear. The shallow water MR near‐surface current accuracy thus matches findings from a previous deep water validation where vertical shear was much weaker.

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Nearshore Monitoring with X-Band Radar: Maximising Utility in Dynamic and Complex Environments

Atkinson¹,

Esteves

Williams

et al. 2020

Preprint

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High-resolution bathymetry estimates via X-band marine radar: 1. beaches

Cited by 39 publications

References 40 publications

On nonhydrostatic coastal model simulations of shear instabilities in a stratified shear flow at high Reynolds number

On nonhydrostatic coastal model simulations of shear instabilities in a stratified shear flow at high Reynolds number

Marine X‐Band Radar Currents and Bathymetry: An Argument for a Wave Number‐Dependent Retrieval Method

Nearshore Monitoring with X-Band Radar: Maximising Utility in Dynamic and Complex Environments

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