SBA系统自阴影效应及其校正方法研究

A core aspect in ocean color remote sensing is to obtain accurate measurement of water-leaving radiance (Lw), therefore the development of methods and systems to achieve high-quality Lw in the field has been a key research subject in ocean optics studies. The applicant of this proposal put forward an innovative scheme (Skylight-blocked approach, SBA) in 2013 to measure Lw directly in the field, and demonstrated the collection of high precision Lw. However, due to the size of the instrument and the measurement strategy and geometry, it is inevitably that Lw measured by SBA contains some effects of self-shading, consequently the accuracy of the obtained Lw is affected. On the other hand, there are limited studies to address the effect of this self-shading; in particular there are no quantifications of its intensity and no relationships showing its association with water properties. More importantly, there have been no methods developed to correct such effects when there are no concurrent measurements of waters’ inherent optical properties. This proposal thus focuses on this self-shading effect, and will use numerical simulations and controlled laboratory measurements to characterize the effect of self-shading on Lw obtained from an SBA system, with an ultimate goal to develop an effective scheme to correct such an effect. This proposal aims at the core and forefront technical challenges in ocean optics and ocean color remote sensing, and the results will significantly improve the practices in measuring Lw in the field. SBA is a game changer.

如何获得准确的现场离水辐亮度（Lw）数据是海洋水色遥感领域的首要技术问题。 2013年本项目申请人提出了一种Lw现场测量的创新方法(Skylight-blocked approach, SBA），是一直接测量而非推算、且获得高精度Lw的方法。然而，SBA作为漂浮式测量系统，难以避免产生自阴影效应，影响Lw 的准确性。而该阴影效应及其对测量的Lw准确性的影响尚未得到全面、定量的分析，因之引起的测量误差难以得到准确的校正。针对这一问题，本项目拟通过蒙特卡洛数值模拟、实验室控制条件与现场天然条件下的多参数精细测量，在大量模拟与测量数据的基础上定量分析不同因素对Lw测量准确性的影响，结合辐射传输理论研究SBA系统的自阴影效应模型，探索采用光谱优化模式进行阴影校正。本项目直指海洋光学与海色遥感界的前沿及核心技术问题，对该领域的发展和应用均有重大意义。

遥感反射比（Rrs）是海洋光学遥感的核心参数，其定义为离水辐亮度（Lw）与入射辐照度的比值。在现场测量中获得准确的离水辐亮度是海洋水色遥感领域的一个重要技术问题，长期未能够有效实现。依据2013年本项目申请人提出的一种Lw现场测量的创新方法(Skylight-blocked approach, SBA），从而使得Lw可以直接测量而非推算、且具有非常高的精度。然而，SBA作为漂浮式测量系统，难以避免产生自阴影效应，影响Lw的准确性。本项目通过蒙特卡洛数值模拟、实验室控制条件与现场天然条件下的多参数精细测量，在大量模拟与测量数据的基础上定量分析不同因素对Lw测量准确性的影响，并结合辐射传输理论研究SBA系统的自阴影效应模型，发展多种算法进行阴影校正，取得理想的Lw现场测量结果。SBA这一新颖测量概念和方法因为其完全改变了传统的测量思路，已经在国际同行产生重大影响。依据SBA概念设计的现场光谱测量设备，已实现商用并交付给多家国内海洋研究/监测机构，为国家科学研究和环境监测做出积极贡献。