@Article{CarvalhoBarbNovoRudo:2015:ImScCo,
author = "Carvalho, Lino Augusto Sander de and Barbosa, Claudio Clemente
Faria and Novo, Evlyn M{\'a}rcia Le{\~a}o de Moraes and Rudorff,
Conrado de Moraes",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto
Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)} and {Instituto Nacional de Pesquisas
Espaciais (INPE)}",
title = "Implications of scatter corrections for absorption measurements on
optical closure of Amazon floodplain lakes using the Spectral
Absorption and Attenuation Meter (AC-S-WETLabs)",
journal = "Remote Sensing of Environment",
year = "2015",
volume = "157",
pages = "123--137",
month = "Feb.",
keywords = "AC-S and Hydroscat corrections, AC-S scattering correction
methods, Amazon floodplain lake, Closure experiment, Inherent
optical properties.",
abstract = "Amazon floodplain lakes range widely in concentrations of
optically active constituents (OAC) driven by seasonality in
hydrological and biogeochemical processes, but in general they are
characterized by high turbidity (NTU from 90 to 1645) compared to
coastal waters. In this work, instruments for measuring inherent
optical properties (IOPs) of water bodies were evaluated for the
first time in floodplain lakes in the lower Amazon River during
the falling limb of the hydrograph. Water column profiles of total
attenuation and absorption were measured using the Spectral
Absorption and Attenuation Meter (AC-S-WETLabs), and of
backscattering using Hydroscat. These measurements, however, are
subject to uncertainties and require corrections for turbid
waters. In this paper, we assessed the implications of scattering
correction methods for the absorption tube, proposed by the AC-S
manufacturer, in the simulation of the Remote Sensing Reflectance
(Rrs). The closure experiment comparing Hydrolight (Mobley \&
Sundman, 2001) simulated Rrs and in situ Rrs demonstrated that
neither of the corrections was able to thoroughly account for the
scattering errors which were propagated to the absorption
measurements with AC-S and backscattering with Hydroscat. The
three scattering correction methods (Flat, Proportional and Kirk)
either under or overestimated the absorption coefficient that
resulted in either under or overestimation of the simulated Rrs.
Flat and Proportional Methods resulted in an underestimation of
Rrs from 400 to 550 nm and overestimation from 600 to 700 nm,
indicating that the assumption of zero (0) absorption in the near
infrared does not apply to inland turbid water. The Rrs errors
varied also according to water OAC composition. Overall, Kirk
correction method provided the best results regarding the spectral
shape of the Rrs, however, failed to account for magnitude. Based
on the tuning tests, the errors in spectra magnitude seem to be
sensitive to the constant fraction of scattering (CFS) used in the
Kirk method. Tests carried out with CFS values varying from 0.18
to 0.38 indicated that magnitude error can be partially overcomed
by tuning CFS according to water composition. Improvements in the
scattering correction methods are required in order to obtain
reliable IOPs in turbid inland Amazon lakes.",
doi = "10.1016/j.rse.2014.06.018",
url = "http://dx.doi.org/10.1016/j.rse.2014.06.018",
issn = "0034-4257",
language = "en",
targetfile = "Implications of scatter.pdf",
urlaccessdate = "27 abr. 2024"
}