Secchi disk depth: A new theory and mechanistic model for underwater visibility

REMOTE SENSING OF ENVIRONMENT

卷:169

Article

Lee, ZhongPing¹  Shang, Shaoling²  Hu, Chuanmin³  Du, Keping⁴  Weidemann, Alan⁵  Hou, Weilin⁵  Lin, Junfang¹  Lin, Gong² 

[1] Univ Massachusetts, Sch Environm, Boston, MA 02125 USA

[2] Xiamen Univ, State Key Lab Marine Environm Sci, Xiamen 361005, Peoples R China

[3] Univ S Florida, Coll Marine Sci, St Petersburg, FL 33701 USA

[4] Beijing Normal Univ, State Key Lab Remote Sensing Sci, Beijing 100875, Peoples R China

[5] Naval Res Lab, Stennis Space Ctr, MS 39529 USA

关键词: Secchi disk depth;    Water transparency;    Visibility theory;    Remote sensing;    Beam attenuation coefficient;    Diffuse attenuation coefficient;   

DOI  :  10.1016/j.rse.2015.08.002

来源: Elsevier

【 摘 要 】

Secchi disk depth (ZsD) is a measure of water transparency, whose interpretation has wide applications from diver visibility to studies of climate change. This transparency has been explained in the past 60 + years with the underwater visibility theory, the branch of the general visibility theory for visual ranging in water. However, through a thorough review of the physical processes involved in visual ranging in water, we show that this theory may not exactly represent the sighting of a Secchi disk by a human eye. Further, we update the Law of Contrast Reduction, a key concept in visibility theory, and develop a new theoretical model to interpret ZsD. Unlike the classical model that relies strongly on the beam attenuation coefficient, the new model relies only on the diffuse attenuation coefficient at a wavelength corresponding to the maximum transparency for such interpretations. This model is subsequently validated using a large (N = 338) dataset of independent measurements covering oceanic, coastal, and lake waters, with results showing excellent agreement (similar to 18% average absolute difference, R-2 = 0.96) between measured and theoretically predicted ZsD ranging from <1 m to >30 m without regional tuning of any model parameters. This study provides a more generalized view of visual ranging, and the mechanistic model is expected to significantly improve the current capacity in monitoring water transparency of the global aquatic environments via satellite remote sensing. (C) 2015 The Authors. Published by Elsevier Inc.

【 授权许可】

Free