基于形态学的海洋激光雷达探测浮游植物优势类群垂直分布的探索研究

浮游植物优势类群垂直分布的快速测量有利于海洋生态趋势分析，相比其它测量方式，海洋激光雷达具有探测海水剖面的优势，但现有方法无法区分类群。针对该问题，本项目采用多波长偏振激光雷达形式，利用多波长处雷达衰减系数、180°后向体散射系数和退偏比与藻类形态的关联性，区分类群。首先基于藻类吸收和散射特性，明确多个有效探测波长；针对水下辐射传输时多次散射对雷达衰减系数和退偏比的影响，建立激光雷达探测剖面修正模型。其次针对多个形态参数同时反演的复杂性，研究将基于藻类形态约束，预先计算激光雷达探测匹配库。通过藻类粒径谱实测、复折射率和最优几何形态参数估计，确定类群形态参数值范围，利用粒子散射模型反推激光雷达探测参数。着重研究类群形态对多波长激光雷达探测参数的影响，阐明其关联性，进而分析类群混合比重对探测的影响，完善优势类群探测方法。该研究将促进对水下辐射传输机制的认识，为浮游植物垂直分布探测拓展新的方法。

The efficient measurement of the vertical distribution of phytoplankton dominant groups facilitates accurate analysis of marine ecological trends. Compared with other measurement methods, ocean Lidar has the advantage of detecting seawater profiles, but the existing Lidar methods cannot distinguish phytoplankton groups. Therefore, in this project, it is proposed to use a multi-wavelength Lidar to detect the vertical distribution of dominant groups, based on the correlation between planktonic algae morphology and Lidar detection parameters, namely Lidar attenuation coefficients, 180 ° back scattering coefficients and depolarization ratios at multiple wavelengths. Firstly, by analyzing the absorption spectra and scattering characteristics of dominant groups, multiple wavelengths, which can be used to detect phytoplankton effectively, are determined. In order to solve the effect of multiple scattering on Lidar attenuation coefficients and depolarization ratios during underwater laser transmission, a Lidar detection profile correction model is established. Secondly, aiming to reduce the complexity of simultaneous inversion of multiple morphological parameters, Lidar detection parameters are pre-computed based on algae morphological constraints, and a matching library of Lidar detection parameters is established. Through measuring the size distributions, and estimating complex refractive indices and optimal morphological parameters of planktonic algae, the value ranges of dominant group morphological parameters are determined, and then the widely-used particle scattering models are used to pre-compute multi-wavelength Lidar detection parameters. Therefore, further analysis will be focused on the influence of dominant group morphology on the multi-wavelength Lidar detection parameters. After clarifying the correlation between morphological parameters and Lidar detection parameters, the effect of planktonic algae mixing ratio on Lidar detection will be analyzed for improving this detection method. This study will contribute to understand the mechanism of underwater radiative transfer and develop a new method for measuring the vertical distribution of planktonic algae in the ocean.