Variability of Relationship Between the Volume Scattering Function at 180^° and the Backscattering Coefficient for Aquatic Particles

Authors

Lianbo Hu, University of North DakotaFollow
Xiaodong Zhang, University of Southern MississippiFollow
Yuanheng Xiong, University of North DakotaFollow
Deric J. Gray, Naval Research Laboratory
Ming Xia He, Ocean University of China

Document Type

Article

Publication Date

4-1-2020

Department

Marine Science

School

Ocean Science and Engineering

Abstract

Properly interpreting lidar (light detection and ranging) signal for characterizing particle distribution relies on a key parameter, (χ_p(π)), which relates the particulate volume scattering function (VSF) at 180° (β_p(π)) that a lidar measures to the particulate backscattering coefficient (b_bp). However, (χ_p(π) has been seldom studied due to challenges in accurately measuring (β_p(π)) and concurrently in the field. In this study, (χ_p(π), as well as its spectral dependence, was re-examined using the VSFs measured in situ at high angular resolution in a wide range of waters. β_p(π), while not measured directly, was inferred using a physically sound, well-validated VSF-inversion method. The effects of particle shape and internal structure on the inversion were tested using three inversion kernels consisting of phase functions computed for particles that are assumed as homogenous sphere, homogenous asymmetric hexahedra, or coated sphere. The reconstructed VSFs using any of the three kernels agreed well with the measured VSFs with a mean percentage difference < 5% at scattering angles < 70°. At angles immediately near or equal to 180°, the reconstructed β_p(π) depends strongly on the inversion kernel. χ_p(π) derived with the sphere kernels was smaller than those derived with the hexahedra kernel but consistent with estimated directly from high-spectral-resolution lidar and in situ backscattering sensor. The possible explanation was that the sphere kernels are able to capture the backscattering enhancement feature near 180° that has been observed for marine particles. χ_p(π) derived using the coated sphere kernel was generally lower than those derived with the homogenous sphere kernel. Our result suggests that χ_p(π) is sensitive to the shape and internal structure of particles and significant error could be induced if a fixed value of χ_p(π) is to be used to interpret lidar signal collected in different waters. On the other hand, χ_p(π) showed little spectral dependence.

Publication Title

Applied Optics

Volume

59

Issue

10

First Page

C31

Last Page

C41

Recommended Citation

Hu, L., Zhang, X., Xiong, Y., Gray, D., He, M. (2020). Variability of Relationship Between the Volume Scattering Function at 180^° and the Backscattering Coefficient for Aquatic Particles. Applied Optics, 59(10), C31-C41.
Available at: https://aquila.usm.edu/fac_pubs/17870