Coefficient of variation of underwater irradiance fluctuations

Weber, V. L.

doi:10.1007/s11141-010-9200-5

Cited by 12 publications

(13 citation statements)

References 4 publications

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“…6a). But the model also shows that higher wind speeds induce stronger fluctuations within the first half metre which is also shown by Weber (2010); this is due to steeper capillary-gravity waves that develop focal points closer to the sea surface. Nikolayev et al (1972) have analyzed the relationship between wind-dependent wave spectra and corresponding energy density spectra of illumination fluctuations at several water depths; they showed the shift of the fluctuation peak towards lower frequencies with increasing depth, and that higher wind speeds have stronger low-frequency peaks and a sharp drop in the spectral density towards higher frequency.…”

Section: Discussion Of the Simulation Resultssupporting

confidence: 54%

“…Nikolayev et al, 1972;Dera and Stramski, 1986;Gernez and Antoine, 2009;Weber, 2010;Hieronymi and Macke, 2010;Darecki et al, 2011). There is general agreement that the most favorable conditions for light focusing by waves prevail at moderate winds between 2 and 7 m s −1 .…”

Section: Discussion Of the Simulation Resultsmentioning

confidence: 97%

“…And yet our model is relatively fast (light fields below more than 100 different wave profiles were investigated for this study). Nikolayev et al, 1972;Weber, 2010;You et al, 2010). However, the PM spectrum applies to gravity waves in a fully developed sea, which means that the wave growth has reached a point of equilibrium with the wind input.…”

Section: Discussion Of the Applied Methodsmentioning

confidence: 99%

“…There are several papers on the relationship between wind conditions and underwater light field fluctuations (e.g. Nikolayev et al, 1972;Dera and Stramski, 1986;Gernez and Antoine, 2009;Weber, 2010;Hieronymi and Macke, 2010;Darecki et al, 2011). The general view is that the most favorable conditions for light…”

Section: Introductionmentioning

confidence: 99%

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On the influence of wind and waves on underwater irradiance fluctuations

Hieronymi

Macke

2012

Ocean Sci.

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Abstract. The influence of various wind and wave conditions on the variability of downwelling irradiance E d (490 nm) in water is subject of this study. The work is based on a two-dimensional Monte Carlo radiative transfer model with high spatial resolution. The model assumes conditions that are ideal for wave focusing, thus simulation results reveal the upper limit for light fluctuations. Local wind primarily determines the steepness of capillary-gravity waves which in turn dominate the irradiance variability near the surface. Down to 3 m depth, maximum irradiance peaks that exceed the mean irradiance E d by a factor of more than 7 can be observed at low wind speeds up to 5 m s −1 . The strength of irradiance fluctuations can be even amplified under the influence of higher ultra-gravity waves; thereby peaks can exceed 11 E d . Sea states influence the light field much deeper; gravity waves can cause considerable irradiance variability even at 100 m depth. The simulation results show that under realistic conditions 50 % radiative enhancements compared to the mean can still occur at 30 m depth. At greater depths, the underwater light variability depends on the wave steepness of the characteristic wave of a sea state; steeper waves cause stronger light fluctuations.

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Section: Discussion Of the Simulation Resultssupporting

confidence: 54%

Section: Discussion Of the Simulation Resultsmentioning

confidence: 97%

Section: Discussion Of the Applied Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the influence of wind and waves on underwater irradiance fluctuations

Hieronymi

Macke

2012

Ocean Sci.

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“…The irregular character of the underwater irradiance distribution is taken into account by implementation of random sea surfaces into the models, that are represented as a superposition of elementary waves from a wave spectrum (e.g. Nikolayev et al, 1972;Yakubenko and Nikolayev, 1977;Weber, 2010;You et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Modeling of wave-induced irradiance variability in the upper ocean mixed layer

Hieronymi

Macke

2012

Ocean Sci.

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Abstract.A Monte Carlo based radiative transfer model has been developed for calculating the availability of solar radiation within the top 100 m of the ocean. The model is optimized for simulations of spatial high resolution downwelling irradiance E d fluctuations that arise from the lensing effect of waves at the water surface. In a first step the accuracy of simulation results has been verified by measurements of the oceanic underwater light field and through intercomparison with an established radiative transfer model. Secondly the potential depth-impact of nonlinear shaped single waves, from capillary to swell waves, is assessed by considering the most favorable conditions for light focusing, i.e. monochromatic light at 490 nm, very clear oceanic water with a low chlorophyll a content of 0.1 mg m −3 and high sun elevation. Finally light fields below irregular wave profiles accounting for realistic sea states were simulated. Our simulation results suggest that under open ocean conditions light flashes with 50 % irradiance enhancements can appear down to 35 m depth, and light variability in the range of ±10 % compared to the mean E d is still possible in 100 m depth.

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Wave‐induced light field fluctuations in measured irradiance depth profiles: A wavelet analysis

Wei

Lewis

Dommelen³

et al. 2014

JGR Oceans

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Rapid variations in the intensities of light are commonly observed in profiles of downwelling plane irradiance in the ocean. These fluctuations are often treated as noise and filtered out. Here an effort is made to extract the pertinent statistics to quantify the light field fluctuations from vertical profiles of irradiance measured under clear skies. The irradiance data are collected in oceanic and coastal waters using a traditional free-fall downwelling plane irradiance sensor. The irradiance profiles are transformed into timefrequency domain with a wavelet technique. Two signatures including the dominant frequency (<3.5 Hz) and the coefficient of variation of irradiance fluctuations along the water column are identified from the variance spectrum. Both the dominant frequency and the amplitude decrease as the inverse square root of depth, consistent with simple models of wave focusing and data from other studies. Mechanisms contributing to the observed variations and the observational uncertainties are discussed.

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Coefficient of variation of underwater irradiance fluctuations

Cited by 12 publications

References 4 publications

On the influence of wind and waves on underwater irradiance fluctuations

On the influence of wind and waves on underwater irradiance fluctuations

Modeling of wave-induced irradiance variability in the upper ocean mixed layer

Wave‐induced light field fluctuations in measured irradiance depth profiles: A wavelet analysis

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