Sunlight induced chlorophyll fluorescence in the near-infrared spectral region in natural waters: Interpretation of the narrow reflectance peak around 761 nm

TitleSunlight induced chlorophyll fluorescence in the near-infrared spectral region in natural waters: Interpretation of the narrow reflectance peak around 761 nm
Publication TypeJournal Article
Year of Publication2016
AuthorsLu Y.C, Li L.H, Hu C.M, Li L., Zhang M.W, Sun S.J, Lv C.G
JournalJournal of Geophysical Research-Oceans
Volume121
Pagination5017-5029
Date Published2016/07
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000383468500035
Keywordsalgorithms; coastal waters; EnMAP; FLEX; fluorescence line height; GEO-CAPE; HyspIRI; inland waters; inversion model; modis; natural waters; o-2 a-band; ocean; PACE; phytoplankton; remote-sensing reflectance; retrieval; sunlight-induced chlorophyll fluorescence
Abstract

Sunlight induced chlorophyll a fluorescence (SICF) can be used as a probe to estimate chlorophyll a concentrations (Chl) and infer phytoplankton physiology. SICF at approximate to 685 nm has been widely applied to studies of natural waters. SICF around 740 nm has been demonstrated to cause a narrow reflectance peak at approximate to 761 nm in the reflectance spectra of terrestrial vegetation. This narrow peak has also been observed in the reflectance spectra of natural waters, but its mechanism and applications have not yet been investigated and it has often been treated as measurement artifacts. In this study, we aimed to interpret this reflectance peak at approximate to 761 nm and discuss its potential applications for remote monitoring of natural waters. A derivative analysis of the spectral reflectance suggests that the 761 nm peak is due to SICF. It was also found that the fluorescence line height (FLH) at 761 nm significantly and linearly correlates with Chl. FLH(761 nm) showed a tighter relationship with Chl than the relationship between FLH(approximate to 685 nm) and Chl mainly due to weaker perturbations by nonalgal materials around 761 nm. While it is not conclusive, a combination of FLH(761 nm) and FLH(approximate to 685 nm) might have some potentials to discriminate cyanobacteria from other phytoplankton due to their different fluorescence responses at the two wavelengths. It was further found that reflectance spectra with a 5 nm spectral resolution are adequate to capture the spectral SICF feature at approximate to 761 nm. These preliminary results suggest that FLH(761 nm) need to be explored more for future applications in optically complex coastal and inland waters.

DOI10.1002/2016jc011797
Short TitleJ Geophys Res-Oceans
Student Publication: 
No
sharknado