In-Water Instrumentation and Platforms for Ocean Color Remote Sensing Applications

Twardowski, Michael; Lewis, Marlon R.; Barnard, Andrew H.; Zaneveld, J. Ronald V.

doi:10.1007/978-1-4020-3100-7_4

Cited by 30 publications

(26 citation statements)

References 121 publications

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“…Several approaches for resolving size distributions are available, although none provide any systematic information on particle composition except scanning electron microscopy coupled with an energy dispersive spectrometer [ Peng et al , 2002, 2007; Groundwater et al , 2012]. All of these techniques require discrete sample collection and suffer associated limitations [ Gardner et al , 1993; Twardowski et al , 2005] except for in situ adaptations of laser diffractometry [ Agrawal and Pottsmith , 2000]. For in situ sampling of bubble size distributions only, the acoustical resonator [ Farmer et al , 1998; Czerski et al , 2011b] and videography [ Deane and Stokes , 1999] have been the most popular approaches, although lower size limits are several and 80 μ m, respectively.…”

Section: Discussionmentioning

confidence: 99%

The optical volume scattering function in a surf zone inverted to derive sediment and bubble particle subpopulations

Twardowski¹,

Zhang

Vagle

et al. 2012

J. Geophys. Res.

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.[1] The effects of particle fields including bubbles on the optical volume scattering function (VSF) were investigated in the surf zone off Scripps Pier as part of an ongoing effort to better understand the underlying dynamics in the VSF in the subsurface ocean. VSFs were measured at 20 Hz at angles spanning 10°-170°in 10°increments with a device called the Multiangle Scattering Optical Tool (MASCOT). Modification of the phase function was observed in passing suspended sediment plumes, wave-injected bubble plumes, and combinations of these particle populations relative to the background. Phase function enhancement in the 60°-80°range was observed in association with bubble plumes, consistent with theoretical predictions. VSFs were inverted to infer size distributions and composition using a least squares minimization fitting procedure applied to a library of phase functions, each representing a lognormally distributed subpopulation with refractive index and coating, where applicable. Phase functions representative of nonspherical mineral particle subpopulations were computed using discrete dipole approximation (DDA) and improved geometric optics method (IGOM) techniques for randomly oriented, asymmetric hexahedra. Phase functions for coated bubbles were computed with the Lorenz-Mie theory. Inversion results exhibited stable solutions that qualitatively agreed with concurrent acoustical measurements of bubbles, aggregate particle size distribution expectations, and anecdotal videography evidence from the field. Although a comparable inversion with a library that assumed spherical shaped particles alone provided less stable results with some incorrectly assigned subpopulations, several dominant subpopulation trends were consistent with the results obtained using nonspherical representations of mineral particles.Citation: Twardowski, M., X. Zhang, S. Vagle, J. Sullivan, S. Freeman, H. Czerski, Y. You, L. Bi, and G. Kattawar (2012), The optical volume scattering function in a surf zone inverted to derive sediment and bubble particle subpopulations,

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Section: Discussionmentioning

confidence: 99%

The optical volume scattering function in a surf zone inverted to derive sediment and bubble particle subpopulations

Twardowski¹,

Zhang

Vagle

et al. 2012

J. Geophys. Res.

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“…CDOM is highly correlated with DOC in arctic rivers and streams [Spencer et al, 2009;Stedmon et al, 2011], allowing for remote sensing to indirectly measure DOC from satellite imagery. Indeed, remote sensing is regularly used in coastal and lake studies to map CDOM [Twardowski et al, 2005;Olmanson et al, 2008]. The spectral properties of a water body are influenced by CDOM, chlorophyll, particulates and detritus, and the water itself, such that field sampling is necessary to create region-specific empirically based algorithms to estimate CDOM [Coble, 2007].…”

Section: Introductionmentioning

confidence: 99%

Spatial and interannual variability of dissolved organic matter in the Kolyma River, East Siberia, observed using satellite imagery

et al. 2011

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The Kolyma River basin in northeastern Siberia, the sixth largest river basin draining to the Arctic Ocean, contains vast reserves of carbon in Pleistocene‐aged permafrost soils. Permafrost degradation, as a result of climate change, may cause shifts in riverine biogeochemistry as this old source of organic matter is exposed. Satellite remote sensing offers an opportunity to complement and extrapolate field sampling of dissolved organic matter in this expansive and remote region. We develop empirically based algorithms that estimate chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) in the Kolyma River and its major tributaries in the vicinity of Cherskiy, Russia. Field samples from July 2008 and 2009 were regressed against spectral data from the Landsat 5 Thematic Mapper and Landsat 7 Enhanced Thematic Mapper‐Plus. A combination of Landsat band 3 and bands 2:1 resulted in an R2 of 0.78 between measured CDOM and satellite‐derived predictions. Owing to the strong correlation between CDOM and DOC, the resulting maps of the region show strong interannual variability of both CDOM and DOC, and important spatial patterns such as mixing zones at river confluences and downstream loading of DOC. Such variability was previously unobserved through field‐based point observations and suggests that current calculations of DOC flux from the Kolyma River to the Arctic Ocean may be underestimates. In this era of rapid climate change, permafrost degradation, and shifts in river discharge, remote sensing of CDOM and DOC offers a powerful, reliable tool to enhance our understanding of carbon cycling in major arctic river systems.

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“…The inherent optical properties (IOPs), which control the propagation of light in water are strongly influenced by the composition of local particulate matter (Bohren and Huffman ; Jonasz and Fournier ). Both active and passive remote sensing rely on interpreting the signature of backscattered light from the ocean to detect algal biomass, “thin layers” with high phytoplankton concentration, suspended particle mass, and to quantify biological primary productivity (Platt and Satyendranath ; Stramski and Kiefer ; Twardowski et al ; Churnside et al ). Thus, characterizing oceanic particulates based on type, size, and shape has been the focus of a multitude of studies over the past several decades (Jackson et al ; Boss et al ; Twardowski et al ; Groundwater et al ; Twardowski et al ).…”

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confidence: 99%

Evidence for ubiquitous preferential particle orientation in representative oceanic shear flows

Nayak

McFarland

Sullivan

et al. 2017

Limnology & Oceanography

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In situ measurements were undertaken to characterize particle fields in undisturbed oceanic environments. Simultaneous, co‐located depth profiles of particle fields and flow characteristics were recorded using a submersible holographic imaging system and an acoustic Doppler velocimeter, under different flow conditions and varying particle concentration loads, typical of those found in coastal oceans and lakes. Nearly one million particles with major axis lengths ranging from ∼14 μm to 11.6 mm, representing diverse shapes, sizes, and aspect ratios were characterized as part of this study. The particle field consisted of marine snow, detrital matter, and phytoplankton, including colonial diatoms, which sometimes formed “thin layers” of high particle abundance. Clear evidence of preferential alignment of particles was seen at all sampling stations, where the orientation probability density function (PDF) peaked at near horizontal angles and coincided with regions of low velocity shear and weak turbulent dissipation rates. Furthermore, PDF values increased with increasing particle aspect ratios, in excellent agreement with models of spheroidal particle motion in simple shear flows. To the best of our knowledge, although preferential particle orientation in the ocean has been reported in two prior cases, our findings represent the first comprehensive field study examining this phenomenon. Evidence of nonrandom particle alignment in aquatic systems has significant consequences to aquatic optics theory and remote sensing, where perfectly random particle orientation and thus isotropic symmetry in optical parameters is assumed. Ecologically, chain‐forming phytoplankton may have evolved to form large aspect ratio chains as a strategy to optimize light harvesting.

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In-Water Instrumentation and Platforms for Ocean Color Remote Sensing Applications

Cited by 30 publications

References 121 publications

The optical volume scattering function in a surf zone inverted to derive sediment and bubble particle subpopulations

The optical volume scattering function in a surf zone inverted to derive sediment and bubble particle subpopulations

Spatial and interannual variability of dissolved organic matter in the Kolyma River, East Siberia, observed using satellite imagery

Evidence for ubiquitous preferential particle orientation in representative oceanic shear flows

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