Implications of scatter corrections for absorption measurements on optical closure of Amazon floodplain lakes using the Spectral Absorption and Attenuation Meter (AC-S-WETLabs)

Carvalho, Lino Augusto Sander de; Barbosa, Cláudio Clemente Faria; Novo, Evlyn Márcia Leão de Moraes; Rudorff, Conrado M.

doi:10.1016/j.rse.2014.06.018

Cited by 24 publications

(19 citation statements)

References 56 publications

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“…where a flat is the absorption corrected by the flat method; a m (λ) is the spectral absorption measured by an ac-s meter; and a m (λ 0 ) is the absorption measured by an ac-s meter at reference wavelength (λ 0 ). In marine waters, 715 nm is commonly used as λ 0 [28]; however, in inland waters, OSC absorption is very high, and therefore, the choice of λ 0 is shifted to longer wavelengths [25,32]. In this work, we used the wavelength at 740 nm as λ 0 , although the temperature strongly affects a(λ) by pure water at around 754 nm [28,43].…”

Section: Scattering Error Correctionmentioning

confidence: 99%

“…Overall, open ocean waters exhibit much lower a(λ) than inland waters due to lower primary productivity and sediments coming from the watershed. Roesler [34] reported a maximum a(412) lower than 2 m −1 for oceanic waters, while Carvalho et al [25] observed a(412) ranging from 8 m −1 to 17 m −1 in the Lago Grande de Curuai (Amazon River), which is a highly turbid water body (turbidity range of 90 NTU to 1645 NTU). Carvalho et al [25] also evaluated some of these correction methods in order to determine the most appropriate for that sort of environment.…”

Section: Introductionmentioning

confidence: 99%

“…Roesler [34] reported a maximum a(412) lower than 2 m −1 for oceanic waters, while Carvalho et al [25] observed a(412) ranging from 8 m −1 to 17 m −1 in the Lago Grande de Curuai (Amazon River), which is a highly turbid water body (turbidity range of 90 NTU to 1645 NTU). Carvalho et al [25] also evaluated some of these correction methods in order to determine the most appropriate for that sort of environment. They [25] simulated R rs using a(λ) corrected from different techniques and compared them with R rs measured in situ to assess the performance of each method.…”

Section: Introductionmentioning

confidence: 99%

“…Martinez-Vicente et al [24] used b(λ) derived by subtracting a(λ) from c(λ) to investigate the spectral behavior and variability of OSCs [24]. Additionally, ac-s data have been used to correct measurements of b b (λ) collected by sensors such as HydroScat-6P (HOBI Labs, Bellevue, WA, USA) and ECO-BB9 (WET Labs Inc., Philomath, OR, USA) [7,25]. These data have been used in research studies about the biogeochemical gradient [10,26,27] and filtration process in cascading reservoir systems [11].…”

Section: Introductionmentioning

confidence: 99%

“…Carvalho et al [25] also evaluated some of these correction methods in order to determine the most appropriate for that sort of environment. They [25] simulated R rs using a(λ) corrected from different techniques and compared them with R rs measured in situ to assess the performance of each method.…”

Section: Introductionmentioning

confidence: 99%

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Assessment of Scattering Error Correction Techniques for AC-S Meter in a Tropical Eutrophic Reservoir

et al. 2018

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Measurements of absorption coefficients (a(λ), in m −1 ) collected by spectrophotometers in situ are overestimated due to the scattering of the reflecting tube absorption meter. Accurate correction of these data is essential in order to characterize water bodies bio-optically, as well as retrieve the remote sensing reflectance (R rs , in sr −1 ), when applying a forward model. There are various methods of scattering error correction; however, they were all developed for clear water. In this research, different techniques were attempted in order to define the most appropriate method for correcting a(λ) values acquired by an absorption and attenuation spectral (ac-s) meter (WET Labs Inc., Philomath, OR, USA) in a tropical eutrophic reservoir. Three methods recommended by the manufacturer of the ac-s meter were tested: "flat" or "baseline", "constant fraction", and "proportional". These methods were applied to two datasets that were measured in May and October 2014. The flat technique exhibited the lowest errors, with an average normalized root mean square error (NRMSE) of 7.95%, and a mean absolute percentage error (MAPE) of 29.26% for May. Meanwhile, proportional was the most suitable technique for most of the samples in October, with a mean NRMSE of 11.19% and a MAPE of 31.03% for October. In addition, the proportional method maintained the shape of the a(λ) values better than the other methods. Despite that, both the flat and proportional methods gave a similar performance statistically. Moreover, the flat method produced the best estimations of chla content for both datasets. Therefore, this method is recommended to correct ac-s data in retrieving such phytoplankton pigments.

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Section: Scattering Error Correctionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Assessment of Scattering Error Correction Techniques for AC-S Meter in a Tropical Eutrophic Reservoir

et al. 2018

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Amazon hydrology from space: scientific advances and future challenges

Fassoni‐Andrade

Fleischmann

Papa³

et al. 2021

Preprint

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As the largest river basin on Earth, the Amazon is of major importance to the world's climate and water resources. Over the past decades, advances in satellite-based remote sensing (RS) have brought our understanding of its terrestrial water cycle and the associated hydrological processes to a new era. Here, we review major studies and the various techniques using satellite RS in the Amazon. We show how RS played a major role in supporting new research and key findings regarding the Amazon water cycle, and how the region became a laboratory for groundbreaking investigations of new satellite retrievals and analyses. At the basin-scale, the understanding of several hydrological processes was only possible with the advent of RS observations, such as the characterization of "rainfall hotspots" in the Andes-Amazon transition, evapotranspiration rates, and variations of surface waters and groundwater storage. These results strongly contribute to the recent advances of hydrological models and to our new understanding of the Amazon water budget and aquatic environments. In the context of upcoming hydrology-oriented satellite missions, which will offer the opportunity for new synergies and new observations with finer space-time resolution, this review aims to guide future research agenda toward integrated monitoring and understanding of the Amazon water from space. Integrated multidisciplinary studies, fostered by international collaborations, set up future directions to tackle the great challenges the Amazon is currently facing, from climate change to increased anthropogenic pressure. Plain Language SummaryThe Amazon basin is the largest river basin in the world, characterized by complex hydrological processes that connect high rates of precipitation, extensive floodplains, dense tropical forests, complex topography, and large variations in freshwater storage and discharge. It plays a key role in the water, energy, and carbon cycles and interacts with the global climate system. Earth observations have played a major role in supporting research in Amazon hydrology, and the characterization of several hydrological processes was only possible with the help of remote sensing data. The basin is now facing great risk under current climate change and increased anthropogenic pressure and the resulting environmental alterations require a better understanding of the overall basin's water cycle across scales. We review the strengths and limitations of observations from satellites in the context of the current and upcoming hydrology-oriented satellite missions, and we make recommendations for improving satellite observations of the Amazon basin water cycle, along with an interdisciplinary and stepwise approach to guide research for the next decades.

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Comparative Study on the Optical Properties of Inland Lakes using IOP and AOP Profiler: A Hyperspectral Remote Sensing and QAA Approach

Sivakumar

Ramaraj

Prasanth

2023

J Indian Soc Remote Sens

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Implications of scatter corrections for absorption measurements on optical closure of Amazon floodplain lakes using the Spectral Absorption and Attenuation Meter (AC-S-WETLabs)

Cited by 24 publications

References 56 publications

Assessment of Scattering Error Correction Techniques for AC-S Meter in a Tropical Eutrophic Reservoir

Assessment of Scattering Error Correction Techniques for AC-S Meter in a Tropical Eutrophic Reservoir

Amazon hydrology from space: scientific advances and future challenges

Comparative Study on the Optical Properties of Inland Lakes using IOP and AOP Profiler: A Hyperspectral Remote Sensing and QAA Approach

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