Oceanic lidar is a powerful tool that can detect the depth-resolved profiles of the upper ocean water. Seawater optical properties are usually retrieved according to the single scattering lidar equation. However

the accuracy of the simplified equation cannot be guaranteed because of the multiple light scattering in the ocean

which calls for an accurate and effective lidar return model. The accuracy of Monte Carlo (MC) simulation gains recognition because of few assumptions. However

MC simulation is limited by its low efficiency. The computation cost in the analytical model decreases. This phenomenon has not been verified in the oceanic lidar. Therefore

evaluating the accuracy of the analytical model is essential.

The principles of the analytical model

conventional MC simulation

and semi-analytic MC simulation were introduced. The analytical model generally depended on the quasi-small-angle approximation. Under such approximation

the radiative transfer equation was solved in the Fourier space using the small angle approximation

which reduced the complexity of the calculation. The conventional MC simulation is based on the purely stochastic construction of an ensemble of photon trajectories through the medium of interest. The semi-analytic approach is used to reduce the statistical error of the conventional MC simulation by combining stochastic and analytic techniques.

The effects of operating parameters

such as the height

field of view

water types

and distribution of phytoplankton layers

on the lidar signals were analyzed and compared. The results showed that the analytical model agrees well with the MC simulation in the homogenous and stratified water. However

in terms of the calculation efficiency

the semi-analytic MC is faster than the conventional MC

and the analytical model is faster than semi-analytic MC. As a result

high accuracy and remarkable efficiency make the analytical model superior in the simulation of the oceanic lidar return.

Methods for simulating oceanic lidar signals

including the analytical model

conventional MC simulation

and semi-analytic MC simulation

were introduced in this paper. Simulations based on these methods were performed under different operating parameters and demonstrated the high accuracy and remarkable efficiency of the analytical model. These advantages make the analytical model superior in the simulation of the oceanic lidar return. The physical mechanism of laser propagation in the water and retrieval of optical parameters based on oceanic lidar will be the prospective objectives based on the method and result in this work.