Collister Brian L, Zimmerman Richard C, Sukenik Charles I, Balch William M, Hill Victoria J
Department of Ocean and Earth Sciences Old Dominion University Norfolk Virginia USA.
Department of Physics Old Dominion University Norfolk Virginia USA.
Limnol Oceanogr. 2022 Jun;67(6):1374-1387. doi: 10.1002/lno.12088. Epub 2022 Apr 29.
Oceanographic lidar measurements of the linear depolarization ratio, , contain information on the bulk characteristics of marine particles that could improve our ability to study ocean biogeochemistry. However, a scarcity of information on the polarized light-scattering properties of marine particles and the lack of a framework for separating single and multiple scattering effects on have hindered the development of polarization-based retrievals of bulk particle properties. To address these knowledge gaps, we made single scattering measurements of for several compositionally and morphologically distinct marine particle assemblages. We then used a bio-optical model to explore the influence of multiple scattering and particle characteristics on lidar measurements of made during an expedition to sample a mesoscale coccolithophore bloom. Laboratory measurements of linear depolarization revealed a complex dependency on particle shape, size, and composition that were consistent with scattering simulations for idealized nonspherical particles. Model results suggested that the variability in measured during the field expedition was driven predominantly by shifts in particle concentration rather than their bulk characteristics. However, model estimates of improved when calcite particles were represented by a distinct particle class, highlighting the influence of bulk particle properties on . To advance polarized lidar retrievals of bulk particle properties and to constrain the uncertainty in satellite lidar retrievals of particulate backscattering, these results point to the need for future efforts to characterize the variability of particulate depolarization in the ocean and to quantify the sensitivity of operational ocean lidar systems to multiple scattering.
海洋激光雷达对线性偏振比的测量包含了海洋颗粒整体特性的信息，这有助于提高我们研究海洋生物地球化学的能力。然而，关于海洋颗粒偏振光散射特性的信息匮乏，以及缺乏一个分离单次散射和多次散射对线性偏振比影响的框架，阻碍了基于偏振的海洋颗粒整体特性反演方法的发展。为了填补这些知识空白，我们对几种成分和形态不同的海洋颗粒组合进行了线性偏振比的单次散射测量。然后，我们使用一个生物光学模型，来探究多次散射和颗粒特性对一次考察期间线性偏振比激光雷达测量结果的影响，此次考察旨在对中尺度颗石藻水华进行采样。线性偏振的实验室测量结果显示，其对颗粒形状、大小和成分存在复杂的依赖性，这与理想化非球形颗粒的散射模拟结果一致。模型结果表明，实地考察期间测量的线性偏振比变化主要是由颗粒浓度变化而非其整体特性驱动的。然而，当方解石颗粒用一个独特的颗粒类别表示时，线性偏振比的模型估计得到了改善，这突出了颗粒整体特性对线性偏振比的影响。为了推进基于偏振的激光雷达对海洋颗粒整体特性的反演，并限制卫星激光雷达对颗粒后向散射反演结果的不确定性，这些结果表明，未来需要努力刻画海洋中颗粒偏振的变化，并量化业务化海洋激光雷达系统对多次散射的敏感性。
