Abstract Assessing the oceanic surface layer's optical properties through CALIOP has been one of the reasons of the extension of the CALIOP mission for 3 more years (2018–2020). This is the first work evaluating the potential use of CALIOP for ocean applications at regional scale in mid-latitude regions (i.e. Mediterranean, MED, and Black Sea, BS) and investigating the added information on ocean particles given by the column integrated depolarization ratio (δT) parameter. We implemented and refined a retrieval procedure to estimate this parameter at 1/4 degree of spatial resolution, comparing 7 years of CALIOP observations (2011–2017) to the corresponding Copernicus multi-sensor L3 ocean colour products of the surface particle backscattering coefficient (bbp) and chlorophyll-a concentration (Chl-a). This study pointed out that the current CALIOP sampling is inadequate to detect subtle day-night difference due to plankton diel variability for these basins. At a basin scale, δT covaries with bbp for bbp ≥ 0.0015 m−1. This is more evident for BS (R = 0.84) than for MED (R = 0.61). The analysis of seasonal distributions confirm this result for BS, where δT has a semi-annual cycle in very good agreement with bbp. In the MED, characterized by different trophic regimes, δT shows also some similarities with Chl-a annual cycle. The combined characterization in the MED bioregions of the annual patterns of bbp:Chl-a, δT:Chl-a and δT:bbp ratios suggested that δT parameter can provide valuable information about the non-sphericity and the size of ocean particles.

中文翻译：

---

地中海和黑海星载激光雷达测量的海洋颗粒光学特性的季节性分布

摘要 通过 CALIOP 评估海洋表层的光学特性一直是 CALIOP 任务延长 3 年（2018-2020 年）的原因之一。这是第一项评估 CALIOP 在中纬度地区（即地中海、MED 和黑海，BS）区域尺度海洋应用的潜在用途并调查由柱积分去极化率给出的关于海洋颗粒的附加信息的第一项工作（ δT) 参数。我们实施并改进了一个检索程序，以 1/4 度的空间分辨率估计该参数，将 7 年的 CALIOP 观测（2011-2017）与相应的哥白尼多传感器 L3 海洋颜色产品的表面粒子背散射系数 (bbp) 进行比较) 和叶绿素-a 浓度 (Chl-a)。这项研究指出，由于这些盆地的浮游生物日夜变化，目前的 CALIOP 采样不足以检测细微的昼夜差异。在盆地尺度上，当 bbp ≥ 0.0015 m-1 时，δT 与 bbp 发生协变。BS (R = 0.84) 比 MED (R = 0.61) 更明显。季节性分布的分析证实了 BS 的这一结果，其中 δT 具有与 bbp 非常一致的半年周期。在以不同营养体系为特征的 MED 中，δT 也显示出与 Chl-a 年循环的一些相似之处。MED 生物区中 bbp:Chl-a、δT:Chl-a 和 δT:bbp 比率的年度模式的综合表征表明，δT 参数可以提供有关海洋颗粒的非球形和大小的有价值的信息。