IOP from reflectance measurements to obtain the Kd coefficient: application to the Gabon and Congo coastal waters

M. Schmeltz; J.-M. Froidefond; F. Jourdain; N. Martiny

doi:10.1117/12.828851

19 August 2009 IOP from reflectance measurements to obtain the Kd coefficient: application to the Gabon and Congo coastal waters

M. Schmeltz, J.-M. Froidefond, F. Jourdain, N. Martiny

Author Affiliations +

Proceedings Volume 7459, Ocean Remote Sensing: Methods and Applications; 74590A (2009) https://doi.org/10.1117/12.828851
Event: SPIE Optical Engineering + Applications, 2009, San Diego, California, United States

Abstract

During the "Optic-Congo" oceanographic survey which took place in 2005 on board the "Beautemp-Beaupré" SHOM vessel, different optical measurements of the surface water were acquired using a TRIOS radiance sensor fixed onboard a mini-catamaran. Hydrological measurements (CTD, fluorescence, attenuation, scattering) and water samples were simultaneously collected in order to measure SPM, Chlorophyll-a and CDOM concentrations. Four types of surface water colours (blue, green-yellow, dark and brown) were identified. The main characteristics of these waters were the very low Chlorophyll-a concentrations for this period of the year (March), and the very high CDOM concentrations along the Congo coast, and particularly in the turbid plume of the Congo River. The attenuation and scattering measurements highlighted the predominance of organic matter at the water surface. These observations were documented using a beam electron microscope and by microanalysis. This data set was used to classify the water bodies along the Gabon and Congo coasts. We propose here to use the remote sensing reflectance (Rrs) measurements to invert the IOP (absorption (a) and backscattering (b_b)) using the WASI numerical bio-optical model. The model is iterative: the Rrs WASI simulations are computed given initial values of ocean constituents' concentrations and iteratively adjusted to the Rrs in-situ measurements. The IOP computations are satisfying when the correlations between simulated and measured Rrs are optimized. Then, the attenuation coefficients (K_d) are computed from the IOP coefficients. These results are compared with measurements of K_u carried out during the survey.

Citation Download Citation

M. Schmeltz, J.-M. Froidefond, F. Jourdain, and N. Martiny "IOP from reflectance measurements to obtain the Kd coefficient: application to the Gabon and Congo coastal waters", Proc. SPIE 7459, Ocean Remote Sensing: Methods and Applications, 74590A (19 August 2009); https://doi.org/10.1117/12.828851

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