Optical properties met in inland waters are mostly governed by the characteristics of the drainage basin and hydrology, resuspension of bottom deposits driven by water motion, or by autochthonous production of primary producers. Due to the optical and spatially complexity of these environments, which in many cases also include the signals reflected by bottom substrates, the description of inland waters by biophysical variables is more accurately when high spectral resolution data are used. In this context, imaging spectroscopy can provides measurements across numerous discrete narrow bands, forming a contiguous spectrum that enables detection and identification of key biophysical properties such as phytoplankton. High spectral resolution data have been successfully used to both assess changing of chlorophylla, which is the pigment common to all living phytoplankton, and to phycoerythrin and phycocyanin, secondary pigments which characterise cyanobacteria. Most of previous studies have been focused on data gathered in the field or on individual hyperspectral image acquisition (with examples from both airborne campaigns and from space, with HICO/Hyperion). Few example exists on assessing phytoplankton from high spectral resolution data collected from ground platforms deployed both in fixed place (to capture the diurnal and daily dynamics) and on ferries operating in coastal zones. The advent of the FLEX mission offers the opportunity to improve retrieval of phytoplankton pigments at synoptic scale at monthly frequency, thanks to hyperspectral measurements from 500 nm to 780 nm within bandwidths of 2 nm collected by the FLORIS sensor. These observations, offer unique opportunity to also trace the effect sun-induced fluorescence from accessory pigments, such as phycoerythrin and phycocyanin fluorescence, that are not currently taken into account in bio-optical modelling or remote sensing studies, Hyperspectral measurements of water leaving radiances, simultaneously gathered from field spectroscopy, APEX and OLCI in both clear and productive waters, are used in this study to show the improvement of phytoplankton pigments retrieval, that could be gathered from the future FLEX/Sentinel-3 Tandem Mission. These data, complemented with bio-chemical measurements from water sampling and radiative transfer HYDROLIGHT model, are used here to address the following items: i) Evaluation of bio-optical modelling inversion to retrieve phytoplankton pigments with a FLORIS like configuration, in terms of band setting and ground sampling distance; ii) Exploration of sun-induced -chlorophyll-a, -phycocyanin and - phycoerythrin fluorescence signals in the hyperspectral measurements for assessing physiological state of the phytoplankton for their use as diagnostic optical markers of cyanobacteria; iii) Assessing the possibility to include the sun-induced fluorescence from secondary pigments in bio-optical modelling for remote sensing algorithms; and finally iv) to outline how the tandem mission (e.g. high revisiting time of Sentinel-3 combined to the monthly observations from FLEX) can meet the measurement requirements of multiple end users for freshwater ecosystem science and management.

Giardino, C., Bresciani, M., Simis, S., Vaiciute, D., Morabito, G., Cogliati, S., et al. (2017). Potential retrieval of phytoplankton pigments in optically complex waters from FLEX/Sentinel-3 Tandem Mission. Intervento presentato a: EARSeL 2017 - EARSeL SIG Imaging Spectroscopy Workshop, Zurich, Switzerland.

Potential retrieval of phytoplankton pigments in optically complex waters from FLEX/Sentinel-3 Tandem Mission

Cogliati, S;Colombo, R
2017

Abstract

Optical properties met in inland waters are mostly governed by the characteristics of the drainage basin and hydrology, resuspension of bottom deposits driven by water motion, or by autochthonous production of primary producers. Due to the optical and spatially complexity of these environments, which in many cases also include the signals reflected by bottom substrates, the description of inland waters by biophysical variables is more accurately when high spectral resolution data are used. In this context, imaging spectroscopy can provides measurements across numerous discrete narrow bands, forming a contiguous spectrum that enables detection and identification of key biophysical properties such as phytoplankton. High spectral resolution data have been successfully used to both assess changing of chlorophylla, which is the pigment common to all living phytoplankton, and to phycoerythrin and phycocyanin, secondary pigments which characterise cyanobacteria. Most of previous studies have been focused on data gathered in the field or on individual hyperspectral image acquisition (with examples from both airborne campaigns and from space, with HICO/Hyperion). Few example exists on assessing phytoplankton from high spectral resolution data collected from ground platforms deployed both in fixed place (to capture the diurnal and daily dynamics) and on ferries operating in coastal zones. The advent of the FLEX mission offers the opportunity to improve retrieval of phytoplankton pigments at synoptic scale at monthly frequency, thanks to hyperspectral measurements from 500 nm to 780 nm within bandwidths of 2 nm collected by the FLORIS sensor. These observations, offer unique opportunity to also trace the effect sun-induced fluorescence from accessory pigments, such as phycoerythrin and phycocyanin fluorescence, that are not currently taken into account in bio-optical modelling or remote sensing studies, Hyperspectral measurements of water leaving radiances, simultaneously gathered from field spectroscopy, APEX and OLCI in both clear and productive waters, are used in this study to show the improvement of phytoplankton pigments retrieval, that could be gathered from the future FLEX/Sentinel-3 Tandem Mission. These data, complemented with bio-chemical measurements from water sampling and radiative transfer HYDROLIGHT model, are used here to address the following items: i) Evaluation of bio-optical modelling inversion to retrieve phytoplankton pigments with a FLORIS like configuration, in terms of band setting and ground sampling distance; ii) Exploration of sun-induced -chlorophyll-a, -phycocyanin and - phycoerythrin fluorescence signals in the hyperspectral measurements for assessing physiological state of the phytoplankton for their use as diagnostic optical markers of cyanobacteria; iii) Assessing the possibility to include the sun-induced fluorescence from secondary pigments in bio-optical modelling for remote sensing algorithms; and finally iv) to outline how the tandem mission (e.g. high revisiting time of Sentinel-3 combined to the monthly observations from FLEX) can meet the measurement requirements of multiple end users for freshwater ecosystem science and management.
abstract + slide
FLEX, Sentinel-2, Fluorescence, Shallow Waters, Phytoplankton, Spectral Fitting
English
EARSeL 2017 - EARSeL SIG Imaging Spectroscopy Workshop
2017
2017
none
Giardino, C., Bresciani, M., Simis, S., Vaiciute, D., Morabito, G., Cogliati, S., et al. (2017). Potential retrieval of phytoplankton pigments in optically complex waters from FLEX/Sentinel-3 Tandem Mission. Intervento presentato a: EARSeL 2017 - EARSeL SIG Imaging Spectroscopy Workshop, Zurich, Switzerland.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/189708
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