Infrared remote sensing of breaking waves

Jessup, Andrew T.; Zappa, Christopher J.; Loewen, Mark; Hesany, V.

doi:10.1038/385052a0

Cited by 162 publications

(97 citation statements)

References 27 publications

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“…[21] On the other hand, a series of studies on sea surface temperatures with infrared imagery by Jessup and his colleagues has revealed that wind-driven microbreaking of ocean waves has a primary role for renewing the surface owing to breaking turbulence, resulting in modulations of the surface temperature [Jessup and Hesany, 1996;Jessup et al, 1997;Wick and Jessup, 1998;Siddiqui et al, 2001;Branch and Jessup, 2007]. The temperature modulation has been observed to appear at different phases in open ocean, which is caused by microbreaking owing to short waves bounded on longer swell waves [Branch and Jessup, 2007].…”

Section: Small-scale Laboratory Experimentsmentioning

confidence: 99%

“…[32] When turbulent wakes are produced by wind wave breaking, Jessup [1995] and Jessup et al [1997] found that surface regions form at temperatures above that of the surrounding area; such regions form a warm patch that extends behind the whitecap. In these situations, a net upward heat flux may form a skin layer on the ocean surface; the skin would be at a higher temperature than the bulk underneath, and therefore when surface turbulence disrupts the skin, the result would be the formation of warm patches on the surface.…”

Section: Patterns Of Surface Temperature On Breaking Wavesmentioning

confidence: 99%

“…[48] Temporal variations in surface renewal and surface recovery were studied by assigning timescales to each using the methods of Jessup et al [1997]. Let T p be the range between the local minimum and maximum temperatures.…”

Section: Transitions Of Surface Temperaturementioning

confidence: 99%

“…If, in addition, the skin layer is disrupted by turbulence, with water beneath the layer emerging into the surface, then local distributions of surface temperature can be used as a signature for the presence of turbulence on the surface. Using infrared imaging of wave faces to measure changes in surface temperature, Jessup et al [1997] studied the energy dissipated in turbulent wakes caused by oceanbreaking waves. They found that the skin-layer recovery rate is directly related to breaking wave turbulence and to the energy dissipation rate.…”

Section: Introductionmentioning

confidence: 99%

“…[6] When the temperature of the air differs from that of the water, heat flux across the sea surface occurs through a thermal boundary layer (skin layer); the thickness of the layer is on the order of 1 mm [Jessup, 1995;Jessup et al, 1997]. When there is a heat flux from the bulk water toward the surface, the temperature in the skin layer is below that of the bulk water; however, when downward heat flux dominates (as, for example, when the surface is heated by sunlight) then the temperature of the skin layer is above that of the bulk.…”

Section: Introductionmentioning

confidence: 99%

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Infrared measurements of surface renewal and subsurface vortices in nearshore breaking waves

Watanabe

Mori

2008

J. Geophys. Res.

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[1] When ocean waves reach a surf zone, jets projecting from the breakers splash sequentially, producing horizontal roller vortices beneath the jets and longitudinal counterrotating vortices behind the rollers; these vortices organize into three-dimensional structures that evolve into a turbulent bore with wave propagation. This disrupts any uniform temperature distributions on the surface, creating heterogeneous patterns of surface temperatures. In this study, we extracted surface temperature distributions from infrared measurements in small-and large-scale wave flumes, then used those data to study the renewed surfaces created by subsurface vortices beneath spilling and plunging breakers. In our large-scale experiments, temporal and spatial scales of surface renewal and surface recovery were consistent with earlier work; however, in our small-scale experiments, the spatial scales showed significant deviations from earlier in situ observations. These inconsistencies may be attributed to scale effects for subsurface vortices, and we show that the Froude number (Fr) can be used to characterize the initial formation of longitudinal counterrotating vortices. Further, for turbulent flows fully developed by wave breaking in a bore region, the frequency of surface renewal correlates exponentially with Reynolds number (Re). The computed vorticity on the breaking wave surface exhibits local patterns which correlate strongly with the gravity induced counterrotating vortices, which in turn renew the rear-facing surface of the breaking waves. In contrast the turbulent bore which precedes the wave crest rapidly disturbs and renews the surface in front of the crest. These two different mechanisms for surface renewal, during the nearshore breaking process, lead to modulations in the surface temperature distribution and changes in thermal diffusivity during the propagation of the breaking wave.Citation: Watanabe, Y., and N. Mori (2008), Infrared measurements of surface renewal and subsurface vortices in nearshore breaking waves,

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Section: Small-scale Laboratory Experimentsmentioning

confidence: 99%

Section: Patterns Of Surface Temperature On Breaking Wavesmentioning

confidence: 99%

Section: Transitions Of Surface Temperaturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Infrared measurements of surface renewal and subsurface vortices in nearshore breaking waves

Watanabe

Mori

2008

J. Geophys. Res.

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Estimating wave energy dissipation in the surf zone using thermal infrared imagery

et al. 2015

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Thermal infrared (IR) imagery is used to quantify the high spatial and temporal variability of dissipation due to wave breaking in the surf zone. The foam produced in an actively breaking crest, or wave roller, has a distinct signature in IR imagery. A retrieval algorithm is developed to detect breaking waves and extract wave roller length using measurements taken during the Surf Zone Optics 2010 experiment at Duck, NC. The remotely derived roller length and an in situ estimate of wave slope are used to estimate dissipation due to wave breaking by means of the wave-resolving model by Duncan (1981). The wave energy dissipation rate estimates show a pattern of increased breaking during low tide over a sand bar, consistent with in situ turbulent kinetic energy dissipation rate estimates from fixed and drifting instruments over the bar. When integrated over the surf zone width, these dissipation rate estimates account for 40-69% of the incoming wave energy flux. The Duncan (1981) estimates agree with those from a dissipation parameterization by Janssen and Battjes (2007), a wave energy dissipation model commonly applied within nearshore circulation models.

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Whitecap lifetime stages from infrared imagery with implications for microwave radiometric measurements of whitecap fraction

Potter¹,

Smith²,

Snow

et al. 2015

JGR Oceans

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Quantifying active and residual whitecap fractions separately can improve parameterizations of air‐sea fluxes associated with breaking waves. We use data from a multi‐instrumental field campaign on Floating Instrument Platform (FLIP) to simultaneously capture the signatures of active and residual whitecaps at visible, infrared (IR), and microwave wavelengths using, respectively, video camera, mid‐IR camera, and a radiometer at 10 GHz. We present results from processing and analyzing IR images and correlating this information with radiometric time series of brightness temperature at horizontal and vertical polarizations TBH and TBV. The results provide evidence that breaking crests and decaying foam appear in mid‐IR as bright and dark pixels clearly distinguishing active from residual whitecaps. We quantify the durations of whitecap lifetime stages from the IR images and identify their corresponding signatures in TB time series. Results show that TBH and TBV vary in phase during the active and in antiphase during the residual whitecap stages. A methodology to distinguish active and residual whitecaps in radiometric time series without a priori IR information has been developed and verified with corresponding IR and video images. The method uses the degree of polarization P (the ratio between the sum and difference of TBV and TBH) to capture whitecaps as prominent spikes. The maximum and zero‐crossing of the first derivative of P serve to identify the presence of active whitecaps, while the minimum of dP marks the transition from active to residual whitecap stage. The findings have implications for radiometric measurements of active and total whitecap fractions.

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Infrared remote sensing of breaking waves

Cited by 162 publications

References 27 publications

Infrared measurements of surface renewal and subsurface vortices in nearshore breaking waves

Infrared measurements of surface renewal and subsurface vortices in nearshore breaking waves

Estimating wave energy dissipation in the surf zone using thermal infrared imagery

Whitecap lifetime stages from infrared imagery with implications for microwave radiometric measurements of whitecap fraction

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