Calculating Reynolds Stresses from ADCP Measurements in the Presence of Surface Gravity Waves Using the Cospectra-Fit Method

Kirincich, Anthony R.; Lentz, Steven J.; Gerbi, Gregory P.

doi:10.1175/2009jtecho682.1

Cited by 30 publications

(89 citation statements)

References 28 publications

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“…Rosman et al (2008) introduced vertical (along beam) and horizontal (beam to beam) adaptive filtering (AF) to improve this method's performance for longer period waves, following a method developed for ADVs by Shaw and Trowbridge (2001). Finally, the cospectra fit (CF) method (Gerbi et al 2008;Kirincich et al 2010) estimates the stress by fitting an established semiempirical turbulence model to below-waveband cospectra. The CF method also provides an estimate of the horizontal length scale of the dominant stress-carrying eddies.…”

Section: Introductionmentioning

confidence: 99%

“…The present work applies two methods-the vertical adaptive filtering method (Rosman et al 2008) and the cospectra fit method (Kirincich et al 2010)-to five datasets, having a range of wave and current characteristics, to determine the conditions under which successful Reynolds stress estimates can be made for each. These methods are applied to previously published ADCP velocity observations from Moorea, French Polynesia, and Santa Barbara, California (Rosman et al 2008); a pair of wave-free estuarine deployments in Elkhorn Slough, California (Nidzieko et al 2006); and the Martha's Vineyard Coastal Observatory (MVCO), Massachusetts (Kirincich et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…These methods are applied to previously published ADCP velocity observations from Moorea, French Polynesia, and Santa Barbara, California (Rosman et al 2008); a pair of wave-free estuarine deployments in Elkhorn Slough, California (Nidzieko et al 2006); and the Martha's Vineyard Coastal Observatory (MVCO), Massachusetts (Kirincich et al 2010). In the present study, the MVCO dataset is expanded to include the weakly stratified (wintertime) portion of a 1.5-yr record of velocity observations, a 30-day portion of which was used by Kirincich et al (2010). Combined, these datasets span a range of possible wave and current conditions in the coastal ocean, and a range of instrument-based noise levels, allowing us to fully evaluate the performance of each method.…”

Section: Introductionmentioning

confidence: 99%

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A Comparison of Methods for Estimating Reynolds Stress from ADCP Measurements in Wavy Environments

Kirincich

Rosman

2011

Journal of Atmospheric and Oceanic Technology

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Turbulent Reynolds stresses are now routinely estimated from acoustic Doppler current profiler (ADCP) measurements in estuaries and tidal channels using the variance method, yet biases due to surface gravity waves limit its use in the coastal ocean. Recent modifications to this method, including spatially filtering velocities to isolate the turbulence from wave velocities and fitting a cospectral model to the below-wave band cospectra, have been used to remove this bias. Individually, each modification performed well for the published test datasets, but a comparative analysis over the range of conditions in the coastal ocean has not yet been performed. This work uses ADCP velocity measurements from five previously published coastal ocean and estuarine datasets, which span a range of wave and current conditions as well as instrument configurations, to directly compare methods for estimating stresses in the presence of waves. The computed stresses from each were compared to bottom stress estimates from a quadratic drag law and, where available, estimates of wind stress. These comparisons, along with an analysis of the cospectra, indicated that spectral fitting performs well when the wave climate is wide-banded and/or multidirectional as well as when instrument noise is high. In contrast, spatial filtering performs better when waves are narrow-banded, low frequency, and when wave orbital velocities are strong relative to currents. However, as spatial filtering uses vertically separated velocity bins to remove the wave bias, spectral fitting is able to resolve stresses over a larger fraction of the water column.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Comparison of Methods for Estimating Reynolds Stress from ADCP Measurements in Wavy Environments

Kirincich

Rosman

2011

Journal of Atmospheric and Oceanic Technology

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“…In such cases, even a small orientation of the instrument's head produces a large wave-induced bias in the estimated variances and covariances from ADCP measurements (Rosman et al 2008). Therefore, several methods have been suggested and applied to accurately calculate Reynolds stresses using ADCPs in the presence of surface gravity waves (Rosman et al 2008;Whipple et al 2006;Kirincich et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Current and turbulence measurements at the FINO1 offshore wind energy site: analysis using 5-beam ADCPs

2017

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We report concurrent measurements of ocean currents and turbulence at two sites in the North Sea, one site at upwind of the FINO1 platform and the other 200-m downwind of the Alpha Ventus wind farm. At each site, mean currents, Reynolds stresses, turbulence intensity and production of turbulent kinetic energy are obtained from two bottom-mounted 5-beam Nortek Signature1000s, high-frequency Doppler current profiler, at a water depth of approximately 30 m. Measurements from the two sites are compared to statistically identify the effects of wind farm and waves on ocean current variability and the turbulent structure in the water column. Profiles of Reynolds stresses are found to be sensible to both environmental forcing and the wind farm wake-induced distortions in both boundary layers near the surface and the seabed. Production of turbulent kinetic energy and turbulence intensity exhibit approximately similar, but less pronounced, patterns in the presence of farm wake effects.

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“…Since surface waves often occupy the same frequency range as marine turbulence, it is difficult to separate the latter from waveinduced velocity fluctuations using simple filtration. Therefore, development of various techniques and methods capable to remove the bias produced by surface waves from ADCP measurements of turbulent shear stress was an important issue over the past decade (Shaw and Trowbridge, 2001;Trowbridge and Elgar, 2003;Whipple et al, 2006;Feddersen and Williams, 2007;Rosman et al, 2008;Schmitt et al, 2009;Huang et al, 2010;Kirincich et al, 2010). This paper addresses two challenges.…”

Section: K a Korotenko Et Al: Effect Of Variable Winds On Current mentioning

confidence: 99%

Effect of variable winds on current structure and Reynolds stresses in a tidal flow: analysis of experimental data in the eastern English Channel

2012

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Abstract. Wind and wave effects on tidal current structure and turbulence throughout the water column are examined using an upward-looking acoustic Doppler current profiler (ADCP). The instrument has been deployed on the seafloor of 18-m mean depth, off the north-eastern French coast in the eastern English Channel, over 12 tidal cycles, and covered the period of the transition from mean spring to neap tide, and forcing regimes varied from calm to moderate storm conditions. During storms, we observed gusty winds with magnitudes reaching 15 m s −1 and wave heights reaching up to 1.3 m. Analysis of velocity spectra revealed a noticeable contribution of wind-induced waves to spectral structure of velocity fluctuations within the subsurface layer. Near the surface, stormy winds and waves produced a significant intensification of velocity fluctuations, particularly when the sustained wind blew against the ebb tide flow. As during wavy periods, the variance-derived Reynolds stress estimates might include a wave-induced contamination, we applied the Variance Fit method to obtain unbiased stresses and other turbulent quantities. Over calm periods, the turbulent quantities usually decreased with height above the seabed. The stresses were found to vary regularly with the predominantly semidiurnal tidal flow. The along-shore stress being generally greater during the flood flow (∼ 2.7 Pa) than during the ebb flow (∼ −0.6 Pa). The turbulent kinetic energy production rate, P , and eddy viscosity, A z , followed a nearly regular cycle with close to a quarter-diurnal period. As for the stresses, near the seabed, we found the maximum values of estimated quantities of P and A z to be 0.1 Wm −3 and 0.5 m 2 s −1 , respectively, during the flood flow. Over the storm periods, we found the highest unbiased stress values (∼ −2.6 Pa) during ebb when tidal currents were opposite to the southwesterly winds while, during the flood, the surface stresses slightly exceeded those estimated for a calm period. A comparison of obtained results gives a good agreement with those of other researchers working on direct measurements of turbulence in tidal flows.

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Calculating Reynolds Stresses from ADCP Measurements in the Presence of Surface Gravity Waves Using the Cospectra-Fit Method

Cited by 30 publications

References 28 publications

A Comparison of Methods for Estimating Reynolds Stress from ADCP Measurements in Wavy Environments

A Comparison of Methods for Estimating Reynolds Stress from ADCP Measurements in Wavy Environments

Current and turbulence measurements at the FINO1 offshore wind energy site: analysis using 5-beam ADCPs

Effect of variable winds on current structure and Reynolds stresses in a tidal flow: analysis of experimental data in the eastern English Channel

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