The vertical diffuse attenuation coefficient Kd (PAR) is used for calculating the euphotic zone, the first optical depth that is important for primary productivity models. Currently, Kd PAR can be estimated using an irradiometer or a Secchi disk (SD). The main objective of this work is to define a model that can be applied to a wide range of optical marine conditions to estimate KdPAR by SD. We used irradiance profiles and SD depth (ZSD) from 679 stations in various marine regions. Three parametric models were developed, and their statistical performance was evaluated in view of previous approaches reported and remote sensing data. The best results were obtained with an adaptive model representing three cases: clear-water, turbid-water, and a transition zone (R² = 0.965, MAE = 0.083, RMSD = 0.239, BIAS = 0.01, and MPI = 0.854). Previous models considering a single optical depth figure at which the SD disappears did not capture the marine optical complexity. Our classification of 113 stations with spectral absorption data into Jerlov water types indicated that no unique correspondence existed between estimated Kd (PAR) and water type, making it ambiguous to associate compatible inherent optical properties and chlorophyll with ZSD. Although obtaining Kd (PAR) from ZSD is simple/low-cost, care should be taken in the methodology used to measure ZSD to ensure consistent results across different optical marine conditions.

中文翻译：

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一种根据Secchi磁盘深度估计扩散衰减系数的新算法

垂直漫射衰减系数Kd（PAR）用于计算共生区，共生区是对初级生产率模型很重要的第一光学深度。当前，可以使用辐照计或Secchi盘（SD）估算Kd PAR。这项工作的主要目的是定义一个模型，该模型可应用于各种光学海洋条件，以通过SD估算KdPAR。我们使用了来自各个海洋地区的679个站的辐照度分布图和SD深度（ZSD）。开发了三个参数模型，并根据先前报告的方法和遥感数据评估了它们的统计性能。使用代表三种情况的自适应模型可获得最佳结果：清水，浑水和过渡带（R ²= 0.965，MAE = 0.083，RMSD = 0.239，BIAS = 0.01，MPI = 0.854）。以前的模型考虑了SD消失的单个光学深度图，却没有反映出海洋光学的复杂性。我们将113个具有光谱吸收数据的站点分类为Jerlov水类型，结果表明估算的Kd（PAR）与水类型之间不存在唯一的对应关系，这使得将兼容的固有光学特性和叶绿素与ZSD关联起来并不明确。尽管从ZSD获取Kd（PAR）是简单/低成本的方法，但应注意用于测量ZSD的方法，以确保在不同的光学海洋条件下获得一致的结果。