Analysis of the Optimal Wavelength for Oceanographic Lidar at the Global Scale Based on the Inherent Optical Properties of Water

Abstract

Understanding the optimal wavelength for detecting the water column profile from a light detection and ranging (lidar) system is important in the design of oceanographic lidar systems. In this research, the optimal wavelength for detecting the water column profile using a lidar system at the global scale was analyzed based on the inherent optical properties of water. In addition, assuming that the lidar system had a premium detection characteristic in its hardware design, the maximum detectable depth using the established optimal wavelength was analyzed and compared with the mixed layer depth measured by Argo data at the global scale. The conclusions drawn are as follows: first, the optimal wavelengths for the lidar system are between the blue and green bands. For the open ocean, the optimal wavelengths are between 420 and 510 nm, and for coastal waters, the optimal wavelengths are between 520 and 580 nm. To obtain the best detection ability using a lidar system, the best configuration is to use a lidar system with multiple bands. In addition, a 490 nm wavelength is recommended when an oceanographic lidar system is used at the global scale with a single wavelength. Second, for the recommended 490 nm band, a lidar system with the 4 attenuating length detection ability can penetrate the mixed layer for 80% of global waters.

Remote Sensing Systems for Ocean: A Review (Part 2: Active Systems)

“…LiDAR instruments are among the airborne/spaceborne active RS systems that can obtain depth-resolved information of ocean layers [255]. Satellite LiDAR systems can operate under thin clouds, between holes in broken clouds, and in polar regions to provide global ocean coverage [252].…”

“…Subsurface ocean measurements have been traditionally conducted using shipborne or airborne instruments [258], [262]- [264]. A specifically designed satellite for oceanographic missions and water column profile data detection has not been launched into space yet, and currently, shipborne and airborne LiDAR systems are employed for ocean studies [255]. Table E summarizes the specifications of spaceborne LiDAR missions.…”

“…LiDAR applications in oceanographic studies cover a wide range of disciplines. Measuring optical properties of water, estimating backscatter coefficient, detecting bubbles, internal waves, planktons, and schools of fish are other applications that have been studied by all types of LiDAR instruments [251], [255], [257], [269]. However, Bathymetric and 3D mapping applications are mainly limited to airborne LiDAR instruments [261], [270], [271].…”

SOLS: An Open-Source Spaceborne Oceanic Lidar Simulator

“…However, it is just a compromise because 532 nm is suitable for coastal water, while it does not work so well in clear open ocean waters that constitute most of the global oceans. It has been shown that a shorter wavelength will be better for open-ocean applications [5,22,26]. However, the estimate of the detection potential capability of spaceborne lidar demands a spaceborne lidar simulator.…”

“…Thus far, several researchers have discussed the laser optimal wavelength, but the impact of background light [26], which may overestimate the penetration depths in open ocean water, has been neglected. Other researchers did not take into account the responsivity of the detector and detector noise [27].…”