Retrieval of Particulate Backscattering Using Field and Satellite Radiometry: Assessment of the QAA Algorithm

Particulate optical backscattering (b(bp)) is a crucial parameter for the study of ocean biology and oceanic carbon estimations. In this work, b(bp) retrieval, by the quasi-analytical algorithm (QAA), is assessed using a large in situ database of matched b(bp) and remote-sensing reflectance (R-rs). The QAA is also applied to satellite R-rs (ESA OC-CCI project) as well, after their validation against in situ R-rs. Additionally, the effect of Raman Scattering on QAA retrievals is studied. Results show negligible biases above random noise when QAA-derived b(bp) is compared to in situ b(bp). In addition, R-rs from the CCI archive shows good agreement with in situ data. The QAA's functional form of spectral backscattering slope, as derived from in situ radiometry, is validated. Finally, we show the importance of correcting for Raman Scattering over clear waters prior to semi-analytical retrieval. Overall, this work demonstrates the high efficiency of QAA in the b(bp) detection in case of both in situ and ocean color data, but it also highlights the necessity to increase the number of observations that are severely under-sampled in respect to others environmental parameters.