Liu Qun, Liu Dong, Bai Jian, Zhang YuPeng, Zhou Yudi, Xu Peituo, Liu Zhipeng, Chen Sijie, Che Haochi, Wu Lan, Shen Yibing, Liu Chong
Opt Express. 2018 Nov 12;26(23):30278-30291. doi: 10.1364/OE.26.030278.
Multiple scattering is an inevitable effect in spaceborne oceanic lidar because of the large footprint size and the high optical density of seawater. The effective attenuation coefficient klidar in the oceanic lidar equation, which indicates the influence of the multiple scattering effect on the formation of lidar returns, is an important parameter in the retrieval of inherent optical properties (IOPs) of seawater. In this paper, the relationships between klidar of the spaceborne lidar signal and the IOPs of seawater are investigated by solving the radiative transfer equation with an improved semianalytic Monte Carlo model. Apart from the geometric loss factors, klidar is found to decrease exponentially with the increase of depth in homogeneous waters. klidar is given as an exponential function of depth and IOPs of seawater. The mean percentage errors between klidar calculated by the exponential function and the simulated ones in three typical stratified waters are within 0.5%, proving the effectiveness and applicability of this klidar-IOPs function. The results in this paper can help researchers have a better understanding of the multiple scattering effect of spaceborne lidar and improve the retrieval accuracy of the IOPs and the chlorophyll concentration of case 1 water from spaceborne lidar measurements.
由于足迹尺寸大以及海水的高光学密度，多次散射是星载海洋激光雷达中不可避免的效应。海洋激光雷达方程中的有效衰减系数klidar表明了多次散射效应在激光雷达回波形成过程中的影响，它是海水固有光学特性（IOPs）反演中的一个重要参数。本文通过使用改进的半解析蒙特卡罗模型求解辐射传输方程，研究了星载激光雷达信号的klidar与海水IOPs之间的关系。除了几何损耗因子外，发现在均匀水体中klidar随深度增加呈指数下降。klidar表示为深度和海水IOPs的指数函数。在三种典型分层水体中，由该指数函数计算得到的klidar与模拟值之间的平均百分比误差在0.5%以内，证明了该klidar - IOPs函数的有效性和适用性。本文的结果有助于研究人员更好地理解星载激光雷达的多次散射效应，并提高从星载激光雷达测量中反演IOPs和一类水体叶绿素浓度的精度。
