Assessment of global detection capability of oceanographic lidar

The profiling of marine bio-optical properties by oceanographic lidar is of great significance to the monitoring of the marine environment and the study of the global carbon cycle. In this study, the global detection capability of oceanographic lidar is analyzed with different specifications. To evaluate the detection performance, a simulator on multi-platform is developed. Based on the quasi-single elastic scattering approximation lidar equation and the bio-optical models, the simulator can generate different kinds of outputs, such as lidar signal profiles, signal-to-noise ratio profiles, maximum detectable depth distributions. The optical properties profiles of the global ocean could be derived from the global chlorophyll-a concentration profile data set, which is used as the input to the simulator. The simulation results are compared with the measurements from airborne lidar in the South China Sea, which verifies the reliability of the simulator. The global detection capability of spaceborne lidar with different power aperture products is simulated, and the influence of laser wavelength is analyzed. The results show that, for the simulated spaceborne lidar with typical specifications at 486 nm, there are probabilities ranging from 0.66 to 0.85 that the upper boundary of the thermocline can be detected on a global scale. In the cleanest open ocean, the lidar has a good capability to penetrate the upper boundary of the thermocline, while it cannot penetrate the subsurface chlorophyll maximum layers, in which the global penetration ratio is 0.93 under the simulation specifications at 486 nm. Finally, the influence of repetition frequency is analyzed, and the results show that reducing the pulse repetition frequency at the same average power can effectively reduce the background light of cumulative profiles and improve the signal-to-noise ratio.