HR: 1400h
AN: OS23E-01    [Abstracts]
TI: Impact of Backscattering Spectra and Fluorescence on NIR Retrieval Algorithms for Coastal Waters
AU: * Ahmed, S A
EM: ahmed@ccny.cuny.edu
AF: The City College of the City University of New York, 140 St & Convent Ave, New York, NY 11223, United States
AU: Gilerson, A
EM: gilerson@ee.ccny.cuny.edu
AF: The City College of the City University of New York, 140 St & Convent Ave, New York, NY 11223, United States
AU: Zhou, J
EM: jzhou@ccny.cuny.edu
AF: The City College of the City University of New York, 140 St & Convent Ave, New York, NY 11223, United States
AU: Hlaing, S
EM: soeminhlaing@gmail.com
AF: The City College of the City University of New York, 140 St & Convent Ave, New York, NY 11223, United States
AU: Ioannou, I
EM: yannismail@gmail.com
AF: The City College of the City University of New York, 140 St & Convent Ave, New York, NY 11223, United States
AU: Jerez, W
EM: zaro33@optonline.net
AF: The City College of the City University of New York, 140 St & Convent Ave, New York, NY 11223, United States
AU: Gross, B
EM: gross@ccny.cuny.edu
AF: The City College of the City University of New York, 140 St & Convent Ave, New York, NY 11223, United States
AU: Moshary, F
EM: moshary@ccny.cuny.edu
AF: The City College of the City University of New York, 140 St & Convent Ave, New York, NY 11223, United States
AB: With the increasing recognition of the need for using the NIR bands for Chl retrieval in coastal waters, the necessity to properly model the water leaving signal in that spectral region is important. In particular, there is a need to account not only for the spectral modulation of the elastic backscatter by the Chl absorption spectra, as it is normally done, but to also take into account the spectral signature of the backscatter itself, whether from mineral or organic particulates, include the contribution of Chl fluorescence and to assess how all these factors affect retrieval algorithms. While approximations for these spectral signatures and magnitudes and sophisticated instruments for their measurement have existed for some time, detailed and accurate information about the interconnection between absorption, scattering spectra and fluorescence contributions to them and comparisons of theory and experimental observations, including field measurements is rarely available. This is especially true for coastal waters, where simultaneous scattering contributions from several particulate components (phytoplankton, detritus and minerals) significantly complicate the issue. To analyze these effects, we have performed numerical simulations using an extensive database of water components appropriate to Case II waters and compared the results of these simulations with the results of field measurement campaigns in the Chesapeake Bay, Long Island and Georgia waters, where hyper-spectral measurements of absorption and extinction were obtained using a WET Labs ACS instrument in conjunction with the bb9 instrument for direct measurement of backscatter, as well as for fluorescence measurement of Chl concentration. The simulations used synthetic datasets created using the HYDROLIGHT radiative transfer code, and where IOP's were connected to parameterized microphysical models in accordance with procedures used to generate the IOCCG dataset, improved by higher (1 nm) spectral resolution and a wider range of parameters typical for coastal waters. Simulations were compared with our recent field measurements. The relevant WET Labs absorption and attenuation data were used as inputs into HYDROLIGHT radiative transfer simulations to obtain the backscattering spectral distributions, using least squares optimization, as a function of Chl and total suspended solids. HYDROLIGHT simulations of elastic reflectance using attenuation/extinction spectra, measured in the field, followed by subtraction from measured field reflectance, permitted retrieval of the fluorescence contribution to the latter, for comparisons with the data set simulations. Generally, the combination of results shows that it is possible to find appropriate bands in the NIR for efficient Chl retrieval. However, the results showed small fluorescence contributions to surface reflectance for mineral concentrations greater than 5 mg/l, because of strong attenuation in the excitation zone and enhanced elastic reflectance making fluorescence detection unrealistic. For lower mineral concentrations, we also find that some combinations of NIR observation bands permit reasonably good FLH retrievals in conditions where specific absorption spectral variation is not very high.
DE: 4855 Phytoplankton
DE: 4863 Sedimentation (1861)
DE: 4894 Instruments, sensors, and techniques
DE: 6969 Remote sensing
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly