scholarly journals An Instrument for In Situ Measuring the Volume Scattering Function of Water: Design, Calibration and Primary Experiments

Sensors ◽  
2012 ◽  
Vol 12 (4) ◽  
pp. 4514-4533 ◽  
Author(s):  
Cai Li ◽  
Wenxi Cao ◽  
Jing Yu ◽  
Tiancun Ke ◽  
Guixin Lu ◽  
...  
Keyword(s):  
Scattering Function ◽  
Volume Scattering

scholarly journals Measurements of the Volume Scattering Function and the Degree of Linear Polarization of Light Scattered by Contrasting Natural Assemblages of Marine Particles

2018 ◽  
Vol 8 (12) ◽  
pp. 2690 ◽  
Author(s):  
Daniel Koestner ◽  
Dariusz Stramski ◽  
Rick Reynolds
Keyword(s):  
Light Scattering ◽  
Linear Polarization ◽  
Suspended Particles ◽  
Mie Scattering ◽  
Natural Seawater ◽  
Laboratory Measurements ◽  
Scattering Function ◽  
Volume Scattering ◽  
Organic Particles

The light scattering properties of seawater play important roles in radiative transfer in the ocean and optically-based methods for characterizing marine suspended particles from in situ and remote sensing measurements. The recently commercialized LISST-VSF instrument is capable of providing in situ or laboratory measurements of the volume scattering function, β p ( ψ ) , and the degree of linear polarization, DoLP p ( ψ ) , associated with particle scattering. These optical quantities of natural particle assemblages have not been measured routinely in past studies. To fully realize the potential of LISST-VSF measurements, we evaluated instrument performance, and developed calibration correction functions from laboratory measurements and Mie scattering calculations for standard polystyrene beads suspended in water. The correction functions were validated with independent measurements. The improved LISST-VSF protocol was applied to measurements of β p ( ψ ) and DoLP p ( ψ ) taken on 17 natural seawater samples from coastal and offshore marine environments characterized by contrasting assemblages of suspended particles. Both β p ( ψ ) and DoLP p ( ψ ) exhibited significant variations related to a broad range of composition and size distribution of particulate assemblages. For example, negative relational trends were observed between the particulate backscattering ratio derived from β p ( ψ ) and increasing proportions of organic particles or phytoplankton in the particulate assemblage. Our results also suggest a potential trend between the maximum values of DoLP p ( ψ ) and particle size metrics, such that a decrease in the maximum DoLP p ( ψ ) tends to be associated with particulate assemblages exhibiting a higher proportion of large-sized particles. Such results have the potential to advance optically-based applications that rely on an understanding of relationships between light scattering and particle properties of natural particulate assemblages.

Measurements and modeling of the volume scattering function in the coastal northern Adriatic Sea

2007 ◽  
Vol 46 (22) ◽  
pp. 5189 ◽  
Author(s):  
Jean-François Berthon ◽  
Eugeny Shybanov ◽  
Michael E.-G. Lee ◽  
Giuseppe Zibordi
Keyword(s):  
Adriatic Sea ◽  
Scattering Function ◽  
Northern Adriatic Sea ◽  
Volume Scattering ◽  
Northern Adriatic

scholarly journals PHIPS-HALO: the airborne Particle Habit Imaging and Polar Scattering probe – Part 3: Single-particle phase discrimination and particle size distribution based on the angular-scattering function

2021 ◽  
Vol 14 (4) ◽  
pp. 3049-3070
Author(s):  
Fritz Waitz ◽  
Martin Schnaiter ◽  
Thomas Leisner ◽  
Emma Järvinen
Keyword(s):  
Particle Size ◽  
Single Particle ◽  
Large Data ◽  
The Arctic ◽  
Scattering Data ◽  
Scattering Function ◽  
Data Set ◽  
Phase Discrimination ◽  
Angular Scattering

Abstract. A major challenge for in situ observations in mixed-phase clouds remains the phase discrimination and sizing of cloud hydrometeors. In this work, we present a new method for determining the phase of individual cloud hydrometeors based on their angular-light-scattering behavior employed by the PHIPS (Particle Habit Imaging and Polar Scattering) airborne cloud probe. The phase discrimination algorithm is based on the difference of distinct features in the angular-scattering function of spherical and aspherical particles. The algorithm is calibrated and evaluated using a large data set gathered during two in situ aircraft campaigns in the Arctic and Southern Ocean. Comparison of the algorithm with manually classified particles showed that we can confidently discriminate between spherical and aspherical particles with a 98 % accuracy. Furthermore, we present a method for deriving particle size distributions based on single-particle angular-scattering data for particles in a size range from 100 µm ≤ D ≤ 700 µm and 20 µm ≤ D ≤ 700 µm for droplets and ice particles, respectively. The functionality of these methods is demonstrated in three representative case studies.

scholarly journals Optical backscattering properties of the "clearest" natural waters

2007 ◽  
Vol 4 (4) ◽  
pp. 2441-2491 ◽  
Author(s):  
M. S. Twardowski ◽  
H. Claustre ◽  
S. A. Freeman ◽  
D. Stramski ◽  
Y. Huot
Keyword(s):  
Natural Waters ◽  
Pure Water ◽  
Pigment Composition ◽  
Scattering Function ◽  
Inherent Optical Properties ◽  
Southeast Pacific ◽  
Order Of Magnitude ◽  
Low Levels ◽  
Reflectance Measurements

Abstract. During the BIOSOPE field campaign October–December 2004, measurements of inherent optical properties from the surface to 500 m depth were made with a ship profiler at stations covering over ~8000 km through the Southeast Pacific Ocean. Data from a ~3000 km section containing the very clearest waters in the central gyre are reported here. The total volume scattering function at 117°, βt(117°), was measured with a WET Labs ECO-BB3 sensor at 462, 532, and 650 nm with estimated uncertainties of 2×10−5, 5×10−6, and 2×10−6 m−1 sr−1, respectively. These values were approximately 6%, 3%, and 3% of the scattering by pure seawater at their respective wavelengths. From a methodological perspective, there were several results: – bbp distributions were resolvable even though some of the values from the central gyre were an order of magnitude lower than the lowest previous measurements in the literature; – Direct in-situ measurements of instrument dark offsets were necessary to accurately resolve backscattering at these low levels; – accurate pure seawater backscattering values are critical in determining particulate backscattering coefficients in the open ocean (not only in these very clear waters); the pure water scattering values determined by Buiteveld et al. (1994) with a [1 + 0.3S/37] adjustment for salinity based on Morel (1974) appear to be the most accurate estimates, with aggregate accuracies as low as a few percent; and – closure was demonstrated with subsurface reflectance measurements reported by Morel et al. (2007) within instrument precisions, a useful factor in validating the backscattering measurements. This methodology enabled several observations with respect to the hydrography and the use of backscattering as a biogeochemical proxy: – The clearest waters sampled were found at depths between 300 and 350 m, from 23.5° S, 118° W to 26° S, 114° W, where total backscattering at 650 nm was not distinguishable from pure seawater; – Distributions of particulate backscattering bbp across the central gyre exhibited a broad particle peak centered ~100 m; – The particulate backscattering ratio typically ranged between 0.4% and 0.6% through the majority of the central gyre from the surface to ~210 m, indicative of "soft" water-filled particles with low bulk refractive index; and – bbp at 532 and 650 nm showed a distinct secondary deeper layer centered ~230 m that was absent in particulate attenuation cp data. The particulate backscattering ratio was significantly higher in this layer than in the rest of the water column, reaching 1.2% in some locations. This high relative backscattering, along with the pigment composition and ecological niche of this layer, appear to be consistent with the coccolithophorid F. profunda. Moreover, results were consistent with several expectations extrapolated from theory and previous work in oceanic and coastal regions, supporting the conclusion that particulate and total backscattering could be resolved in these extremely clear natural waters.

Sign in / Sign up

Export Citation Format

Share Document