Raman Remote Sensing Of The Ocean Mixed-Layer Depth

Leonard, Donald A.; Caputo, Bernard

doi:10.1117/12.7973107

Cited by 10 publications

(8 citation statements)

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“…Because the Raman-shifted light is strongly absorbed when 532-nm illumination is used, measurements have used shorter-wavelength lasers [123][124][125][126] unless only near-surface values are required. 127,128 Using this technique, temperature profiles have been measured to 30 m using a 450-nm laser on a ship.…”

Section: Temperaturementioning

confidence: 99%

Review of profiling oceanographic lidar

Churnside

2013

Opt. Eng

145

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This paper provides a review of the development of profiling oceanographic lidars. These can provide quantitative profiles of the optical properties of the water column to depths of 20 to 30 m in productive coastal waters and to depths of 100 m for a blue lidar in the open ocean. The properties that can be measured include beam attenuation, diffuse attenuation, absorption, volume scattering at the scattering angle of 180 deg, and total backscattering. Lidar can be used to infer the relative vertical distributions of fish, plankton, bubbles, and other scattering particles. Using scattering as a tracer, lidar can provide information on the dynamics of the upper ocean, including mixed-layer depth, internal waves, and turbulence. Information in the polarization of the lidar return has been critical to the success of many of these investigations. Future progress in the field is likely through a better understanding of the variability of the lidar ratio and the application of high-spectral-resolution lidar to the ocean. Somewhat farther into the future, capabilities are likely to include lidar profiling of temperature in the ocean and an oceanographic lidar in space.

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Section: Temperaturementioning

confidence: 99%

Review of profiling oceanographic lidar

Churnside

2013

Opt. Eng

145

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“…In [19], polarized Raman components were acquired from a saline solution (NaCl 40%) and used for estimating depolarization markers, achieving theoretical accuracies of ±0.5 °C for temperature predictions. Later, the same temperature prediction accuracies of ±0.5 °C were achieved when collecting Raman spectra from water excited by a 470 nm laser [24]. Many Raman spectrometers, including the one used to acquire Figure 1, do not allow for simultaneous acquisition of orthogonally-polarized spectral components.…”

Section: Introductionmentioning

confidence: 99%

A LIDAR-Compatible, Multichannel Raman Spectrometer for Remote Sensing of Water Temperature

Ribeiro

Artlett

Pask

2019

Sensors

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The design and operation of a custom-built LIDAR-compatible, four-channel Raman spectrometer integrated to a 532 nm pulsed laser is presented. The multichannel design allowed for simultaneous collection of Raman photons at two spectral regions identified as highly sensitive to changes in water temperature. For each of these spectral bands, the signals having polarization parallel to (∥) and perpendicular to (⟂), the excitation polarization were collected. Four independent temperature markers were calculated from the Raman signals: two-colour(∥), two-colour(⟂), depolarization(A) and depolarization(B). A total of sixteen datasets were analysed for one ultrapure (Milli-Q) and three samples of natural water. Temperature accuracies of ±0.4 °C–±0.8 °C were achieved using the two-colour(∥) marker. When multiple linear regression models were constructed (linear combination) utilizing all simultaneously acquired temperature markers, improved accuracies of ±0.3 °C–±0.7 °C were achieved.

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“…Additionally, these were the markers which exhibited lowest absolute % errors [0.04% for two-color(||) and 0.09% for depolarisation(A)] and the best RMSTEs of ±0.5 • C were found for both markers. Sensitivity values were generally smaller than the 1%/ • C reported by the authors of Chang and Young (1972) and Leonard and Caputo (1983), however, it is necessary to consider the impact of the spectral channels widths on the final sensitivities. The authors of Artlett and Pask (2015) evaluated the trade-offs between spectral channels and sensitivities by performing simulations with unpolarized Raman signals acquired from ultrapure (Reverse-Osmosis) water samples.…”

Section: Milli-q Water Analysismentioning

confidence: 62%

“…There is a lack of LIDAR-compatible studies in the Raman remote sensing of water temperature using blue lasers, restricting the discussion of the results from this article to comparisons with the reports of Leonard and Caputo (1983). In the occasion, the authors reported the use of a LIDAR-compatible custombuilt RS integrated to a 470 nm laser (15 mJ per pulse, 2 kHz repetition rate) measuring water temperature in laboratory from depolarisation markers and finding accuracies of ±0.5 • C. These were the same accuracies found for our multichannel blue RS when measuring Milli-Q water temperature from depolarisation(A) information.…”

Section: Milli-q Water Analysismentioning

confidence: 99%

“…These markers can be calculated from Raman signals having the same polarization state and are known as "two-color" ratios, or from the number of photons having perpendicular/parallel polarization, referred to as "depolarisation" ratios. These ratios form the basis for numerous studies undertaken from the 1970s until the present time, aimed at using Raman spectroscopy to remotely determine water temperature (Chang and Young, 1972;Leonard et al, 1979;Leonard and Caputo, 1983;Artlett and Pask, 2015). When used in combination with LIDAR methods, there exists great potential to obtain depth-resolved measurements of subsurface water temperature.…”

Section: Introductionmentioning

confidence: 99%

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Remote Sensing of Natural Waters Using a Multichannel, Lidar-Compatible Raman Spectrometer and Blue Excitation

Ribeiro

Pask

2020

Front. Mar. Sci.

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The design and operation of a custom-built LIDAR-compatible, four-channel Raman spectrometer integrated to a 473 nm pulsed laser is presented. The multichannel design allowed for simultaneous collection of Raman photons at spectral regions identified as highly sensitive to changes in water temperature. Four independent temperature markers were calculated for ultrapure (Milli-Q) and natural water samples [two-color(||), two-color(⊥), depolarisation(A), and depolarisation(B)]. Temperature accuracies of up to ±0.5 • C were achieved for both water types when predicted by two-color(||) markers. Multiple linear regression models were constructed considering all simultaneously acquired temperature markers, resulting in improved accuracies of up to ±0.2 • C. The potential benefits of blue laser excitation in relation to avoiding overlap between the Raman signal and fluorescence by chlorophyll-a are discussed, along with the higher Raman returns anticipated compared to the more-conventional green laser excitation.

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Raman Remote Sensing Of The Ocean Mixed-Layer Depth

Cited by 10 publications

References 0 publications

Review of profiling oceanographic lidar

Review of profiling oceanographic lidar

A LIDAR-Compatible, Multichannel Raman Spectrometer for Remote Sensing of Water Temperature

Remote Sensing of Natural Waters Using a Multichannel, Lidar-Compatible Raman Spectrometer and Blue Excitation

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