Remote sensing algorithms of seawater transparency: A review

Water transparency (or Secchi Disk depth: SDD) is a key parameter in ocean color remote sensing, which plays an important role in water environments. Measuring water clarity in traditional method is sparse and discrete, however, advancement in satellite sensors overcomes this shortcoming. Using remote sensing to monitor water clarity of the waters has becoming a popular topic in the field of oceanography. Many studies have been focused on the inversion algorithms of SDD. A variety of remote sensing algorithms for estimating SDD were proposed, including empirical and semi-analytical models. In this study, we summarize the research progress of these two inversion models at home and abroad in recent years. Empirical algorithms are established by optical properties of water and semi-analytic algorithms are combined physical theories. Based on this principle, current algorithms for retrieving SDD were categorized and compared. According to the major problems of retrieval algorithms, future researches should focus on integrating multi-source remote sensing data, improving QAA (Quasi-Analytical Algorithm), and in-depth analysis of the relationship between optical parameters and SDD, in order to establish the inversion algorithm with high precision and high versatility. This paper can provide a reference for the research of SDD remote sensing inversion algorithm.