POSTER SESSION 4
10:30–12:30, Thursday, September 17
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
ABSTRACT 1189 | POSTER 212
IS THE SECCHI DISK DEPTH DETERMINED BY THE CONTRAST BETWEEN THE DISK EDGE AND THE BACKGROUND WATER?
Secchi disk depth (Zsd) has long been interpreted through competing theories that attribute disk disappearance either to attenuation of edge contrast between the disk boundary and the surrounding water or to loss of whole-disk reflectance contrast against the background field. Direct experimental validation of these mechanisms, however, remains limited. In this study, field measurements and Monte Carlo simulations were conducted using both disk and ring Secchi targets to isolate the role of edge contrast in Zsd evaluation. Results show that Secchi depth measured with the disk target (Zsd-disk) exceeds that measured with the ring target (Zsd-ring). Zsd-disk correlates primarily with the diffuse attenuation coefficient (Kd), whereas Zsd-ring exhibits additional dependence on the beam attenuation coefficient (c), indicating target contrast mechanism is determined by the target angular scale. Simulations further quantified the contrast attenuation (K), revealing strong dependence on absorption and increased sensitivity to scattering for small-angular targets. These findings show that Zsd is not determined solely by edge contrast, but depends on contrast governed by target geometry and the optical properties of water.
Zhehai Shang, Ocean University of China, [email protected]
Zhongping Lee, Xiamen University, [email protected]
Shaoling Shang, Xiamen University, [email protected]
Shuguo Chen, Ocean University of China, [email protected]
Poster Session | 1 | 2 | 3 | 4 | Schedule at a Glance
