Estimation of the Secchi disk depth from the NASA MODIS-Aqua diffuse attenuation coefficient data in the northern Persian Gulf and the Gulf of Oman: A spatiotemporal assessment

This study aimed to propose a method for the estimation of Secchi disk depth ( Zsd) values in northern Persian Gulf, Strait Hormuz, and Gulf Oman (N-PG-SH-GO), based on MODIS-Kd(490) data. The field-observed Zsd were collected during seven research cruises conducted by vessel between 2018 2021. A total number 114 observed 68 stations. daily Kd(490) MODIS-Aqua/L2 data downloaded all days (± three), wherein available. Different fitting models examined estimate from Kd(490). 73 first six utilized optimum model, 41 stations, last cruise used validation results. Upon designating method, then employed create final model. results demonstrated that power model is optimal (R2=0.81 RMSE = 2.04 m), so form Zsd=0.34 Kd(490)−1.42 might be compute N-PG-SH-GO. was determine monthly seasonal assess spatiotemporal variation water clarity showed annual domain N-GO extremely higher than N-PG N-SH maximum minimum respectively occurred warm months colder ones. Compared with N-GO, average lower where mean N-PG, N-SH, determined as 8.91, 6.27, 10.27 m, respectively.