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First experiences with the Landsat-8 aquatic reflectance product: evaluation of the regional and ocean color algorithms in a coastal environment

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posted on 2023-06-07, 07:22 authored by Majid Nazeer, Muhammad Bilal, Janet Elizabeth Nichol, Weicheng Wu, Mohammad M M Alsahili, Muhammad Imran Shahzad, Bijoy Krishna Gayen
Since the launch of the Landsat-8 (L8) Operational Land Imager (OLI) on February 11, 2013, there has been a continuous effort to produce reliable ocean color products by taking the advantages of its medium spatial resolution (30 m) and higher Signal to Noise Ratio (SNR). A Provisional Aquatic Reflectance product for the L8 OLI (L8PAR) has been recently released to the public to explore its potential for ocean color applications. This study used a six-year data record of L8 for development of a regionally tuned algorithm (RTA20) for estimating Chlorophyll-a (Chl-a) concentrations around the complex coastal environment of Hong Kong, and is the first to report the usability of the L8PAR product for coastal areas. Furthermore, this study validated three previously developed algorithms, namely RTA16, RTA17 and RTA19, and two ocean color algorithms (OC2 and OC3) modified for L8 OLI by NASA’s Ocean Color group. Results indicate that the newly released L8PAR product has a high potential for estimating the coastal water Chl-a concentrations with higher detail and higher accuracy than previously. The RTA20 algorithm developed in this study outperformed the previous algorithms (RTA16, RTA17, RTA19, OC2 and OC3), e.g., with lower values for Root Mean Square Error (RMSE; 0.92 mg/m3), bias (-0.26 mg/m3) and mean ratio (1.29). Although inferior to the RTA20, the OC2 algorithm also performed well in terms of Pearson’s correlation coefficient (r; 0.84), slope (6.87) and intercept (-8.44) while for RTA20 the values for r, slope and intercept were 0.96, 0.77 and 0.27, respectively. This preliminary evaluation reveals that the OC2 algorithm can be used as an operational algorithm for L8 Chl-a product generation for global coastal areas while RTA20 can be used as a regional algorithm for the routine monitoring of Chl-a concentrations around the coastal areas of Hong Kong or for coastal areas with similar water quality elsewhere in the world.

History

Publication status

  • Published

File Version

  • Accepted version

Journal

Remote Sensing

ISSN

2072-4292

Publisher

MDPI AG

Issue

12

Volume

12

Article number

a1938

Pages

11.0

Department affiliated with

  • Geography Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2020-06-29

First Open Access (FOA) Date

2020-06-29

First Compliant Deposit (FCD) Date

2020-06-29

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