Turbidity maximum zone index: a novel model for remote extraction of the turbidity maximum zone in different estuaries
<p>An efficient recognition and extraction of the estuarine turbidity maximum zone (TMZ) is important for studying terrestrial hydrological processes. Although many studies relevant to the TMZ have been conducted worldwide, the extraction methods and criteria used to describe the TMZ vary sign...
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| Autores principales: | , , , , , , , , , , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/563ba4fb68a0437bbcb130757311010a |
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| Sumario: | <p>An efficient recognition and extraction of the estuarine
turbidity maximum zone (TMZ) is important for studying terrestrial
hydrological processes. Although many studies relevant to the TMZ have been
conducted worldwide, the extraction methods and criteria used to describe
the TMZ vary significantly both spatially and temporally. To improve the
applicability of the methods adopted in previous studies and to develop a
novel model to accurately extract the TMZ in multiple estuaries and different
seasons from remote-sensing imageries, this study estimated the total
suspended solid (TSS) and chlorophyll <span class="inline-formula"><i>a</i></span> (Chl <span class="inline-formula"><i>a</i></span>) concentrations in three
estuaries. These were the Pearl River estuary (PRE), the Hanjiang River estuary (HRE), and the Moyangjiang River estuary (MRE) of Guangdong
Province, China. The spatial distribution characteristics of the TSS and
Chl <span class="inline-formula"><i>a</i></span> concentrations were analyzed. A nearly opposite association was found
between the TSS and Chl <span class="inline-formula"><i>a</i></span> concentrations in the three estuaries, particularly
in the PRE. The regions with high (low) TSS concentrations had relatively
low (high) Chl <span class="inline-formula"><i>a</i></span> concentrations and, therefore, a turbidity maximum zone index
(TMZI), defined as the ratio of the difference and sum of the logarithmic
transformation of the TSS and Chl <span class="inline-formula"><i>a</i></span> concentrations, was firstly proposed. By
calculating the TMZI values in the PRE on 20 November 2004 (low-flow
season), it was found that the criterion <span class="inline-formula">TMZI>0.2</span> could be
used to identify the TMZs of the PRE effectively. The TMZ extraction results
were generally consistent with the visual-interpretation results. The
area-based accuracy measures showed that the quality (<span class="inline-formula"><i>Q</i></span>) of the extraction
reached 0.8429. The same criterion was applied in the PRE on 18 October
2015 (high-flow season), and high accuracy and consistency across seasons
were observed (<span class="inline-formula"><i>Q</i>=0.8171</span>). The western shoal of the PRE was the main
distribution area of TMZs. Extracting TMZs by the newly proposed index
performed well in different estuaries and on different dates (HRE on
13 August 2008 in the high-flow season and MRE on 6 December 2013 in the low-flow
season). Compared to the previous fixed threshold of TSS or turbidity
methods, extracting the TMZ using the TMZI had higher accuracy and better
applicability (<span class="inline-formula"><i>Q</i></span>: 0.1046–0.4770 vs. 0.8171–0.8429). Evidently, this
unified TMZI is potentially an optimized method for the global monitoring
and extraction of TMZs of estuaries from different satellite remote-sensing
imageries. It can be used to help the understanding of the spatial and
temporal variation in TMZs and estuarine processes at regional and global
scales as well as improve the<span id="page6834"/> management and sustainable development of
regional society and the natural environment.</p> |
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