Design of the Ship-Borne Multi-Wavelength Polarization Ocean Lidar System and Measurement of Seawater Optical Properties

Qi Liu,Xiaoquan Song,Kailin Zhang,Songhua Wu,Jintao Liu,Bingyi Liu,Peizhi Zhu,Xiangcheng Chen,D Liu,Y Wang,F Moshary,B Gross,Y Wu

doi:10.1051/epjconf/202023707007

Abstract

A ship-borne multi-wavelength polarization ocean lidar system LOOP (Lidar for Ocean Optics Profiler) is introduced in detail, aiming to obtain high-precision vertical profiles of seawater optical characteristics. Based on Monte-Carlo simulation, the receiving telescope is designed with a variable field of view, producing system attenuation coefficient (Klidar) approximating the optical parameters of seawater under a different field of view and water body conditions. At first, a sea trial was conducted in Jiaozhou Bay, and the measured diffuse attenuation coefficient (Kd) of seawater was 0.3m−1, being in good agreement compared with the results measured by field instrument TriOS. Then a field campaign was organized in the South China Sea. The measurement of the seawater diffuse attenuation (Kd) was 0.035m−1. These results support the prospects that lidar, as an effective tool supplement to traditional passive ocean color remote sensing, can provide the vertical distributions of optical properties in the upper ocean.

Highlights

The return signal travels to the five regular channels through beam splitters and narrow-band interference filters positioned at the front of photomultiplier tubes (PMT)
The prototype of the LOOP system was first compared with the field instrument TriOS to obtain the optical properties profile of the coastal water column on July 30, 2018
As the system was deployed above water on the boat, when the laser emitted with high energy, the specular return off the sea surface cause digitizer saturation that cannot obtain the signal of the water column even to 20m below the surface

Summary

Introduction

Lidar using the blue-green band laser can penetrate the water body, which can directly and accurately obtain the high-precision vertical profile of seawater optical properties [6], making up for the limitations of in-situ optical The results in Jiaozhou optical properties of solutes and particles in Bay and the South China Sea and case studies are seawater vary with the type and concentrationprovided in Sect. Utilizing three-wavelength Nd:YAG narrow pulse laser with high energy, the LOOP system has five regular channels including 355 nm parallel-cross polarization, 532 nm parallel-cross polarization and 1064nm.

Results

Conclusion