Polarized lidar and ocean particles: insights from a mesoscale coccolithophore bloom
Polarized lidar and ocean particles: insights from a mesoscale coccolithophore bloom
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DOI：
10.1364/ao.389845
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发表时间：
2020-05-20
期刊：
影响因子：
1.9
通讯作者：
Balch, William M.
中科院分区：
文献类型：
--
作者：
Collister, Brian L.;Zimmerman, Richard C.;Balch, William M.
海洋激光雷达能够对天然水体中悬浮颗粒的垂直分布进行远程估算，这可能会彻底改变我们描述海洋生态系统特征以及在上层海洋生物地球化学模型中恰当呈现它们的能力。然而，激光雷达信号对水柱固有光学特性（IOPs）和仪器特性存在复杂的依赖关系，这使得从激光雷达回波信号中获取有意义的生物地球化学特性的工作变得复杂。在这项研究中，我们使用一种船基系统来测量激光雷达衰减系数（α）和线性退偏比（δ），测量范围涵盖各种在光学和生物地球化学方面不同的水体，包括浑浊的沿海水体、清澈的贫营养水体以及与中尺度颗石藻水华相关的富含方解石的水体。在航行过程中持续测量海面的固有光学特性，以描述α和δ对颗粒丰度和组成变化的响应。α的大小与漫射衰减系数（K - d）一致，尽管α与K - d的关系是非线性的。δ与散射光学深度以及后向散射的方解石比例呈正相关。对这些数据的统计拟合表明，钙化颗粒的偏振散射特性是独特的，并导致激光雷达退偏比出现可测量的差异。更好地理解颗石藻和其他海洋颗粒的偏振散射特性将提高我们解释偏振海洋激光雷达测量结果的能力，并可能催生远程测量海洋颗粒物质特性的新技术。（C）2020美国光学学会
Oceanographic lidar can provide remote estimates of the vertical distribution of suspended particles in natural waters, potentially revolutionizing our ability to characterize marine ecosystems and properly represent them in models of upper ocean biogeochemistry. However, lidar signals exhibit complex dependencies on water column inherent optical properties (IOPs) and instrument characteristics, which complicate efforts to derive meaningful biogeochemical properties from lidar return signals. In this study, we used a ship-based system to measure the lidar attenuation coefficient (alpha) and linear depolarization ratio (delta) across a variety of optically and biogeochemically distinct water masses, including turbid coastal waters, clear oligotrophic waters, and calcite rich waters associated with a mesoscale coccolithophore bloom. Sea surface IOPs were measured continuously while underway to characterize the response of alpha and delta to changes in particle abundance and composition. The magnitude of alpha was consistent with the diffuse attenuation coefficient (K-d), though the alpha versus K-d relationship was nonlinear. delta was positively related to the scattering optical depth and the calcite fraction of backscattering. A statistical fit to these data suggests that the polarized scattering properties of calcified particles are distinct and contribute to measurable differences in the lidar depolarization ratio. A better understanding of the polarized scattering properties of coccolithophores and other marine particles will further our ability to interpret polarized oceanographic lidar measurements and may lead to new techniques for measuring the material properties of marine particles remotely. (C) 2020 Optical Society of America