Comparison of chlorophyll a concentration detected by remote sensors and other chlorophyll indices in inhomogeneous turbid waters

Abstract

A new analytical approach for retrieval of the vertically weighted chlorophyll a concentration (<linear span>Chl<linear span>(rs)) detected by remote sensors is presented. Model calculations were carried out for the turbid waters of Lake Kinneret, Israel, and showed that <linear span>Chl<linear span>(rs) may be replaced by the average chlorophyll a concentration (<linear span>Chl<linear span>(p)) within the upper "penetration layer" 0-Z(p). The study also showed a high correlation between <linear span>Chl<linear span>(rs) and Chl concentration averaged in the other depth layers, namely, the 0-1 m layer, the euphotic layer (0-Z(e)), and the production layer (0-Z(pr)). Our findings are closely related to models developed for the world ocean, with the exception of periods when the dinoflagellate Peridinium gatunense blooms in the lake. We showed the effect of the pattern of vertical Chl distributions within the penetration layer on the difference between <linear span>Chl<linear span>(rs) and other Chl indices was conspicuous when the Chl maximum was in the uppermost 0- m layer of the water column. We assume that the presented approaches are instrumental for further development of optimal, locally adapted algorithms for remote sensing of Chl in any type of natural waters.

Application of remote sensing for the optimization of in-situ sampling for monitoring of phytoplankton abundance in a large lake

“…This means that the portion of water-leaving radiance backscattered from individual layers decreases with depth, unless a turbid layer is covered by clearer water. Appropriate weighting can be applied to reference profile measurements if vertically resolved attenuation measurements are available (Odermatt et al, 2012a;Sokoletsky and Yacobi, 2011). Due to the lack of such measurements, we average the reference profile measurements taken at 0-5 m as in earlier studies with comparable reference data (Odermatt et al, 2010).…”

Evaluation of Weighting Average Functions as a Simplification of the Radiative Transfer Simulation in Vertically Inhomogeneous Eutrophic Waters

“…where Fr(z 1 , z 2 ) is the fraction of r rs (λ, 0 − ) at the layer between z 1 m and z 2 m, g x (z) is the average weighting function. Three weighting average functions, namely, g GC [8], g Z [10], and g S [9], are as follows:…”

“…The relationship between b b (z)/(a(z) + b b (z)) in each water depth and r rs (0 − ) could explain the effects of vertical distribution of phytoplankton on underwater light field. Several approaches have been proposed to reduce the effects of vertical distribution of phytoplankton on R rs (λ) [9,10,17]. The R rs (λ) of stratified Case I waters was interpreted and found to be identical to that of hypothetical homogeneous waters with phytoplankton pigment concentration (C rs ), which is a depth-weighted average of the actual profiles of pigment concentration [8].…”

“…Pitarch et al [41] added a degree of freedom between the aforementioned two functions [8,10] to retrieve vertical profiles of the total suspended matter concentration. Besides, the average Chla(z) within the penetration layer or certain water depth was used to replace the vertically weighted Chla in Lake Kinneret [9].…”

An approach to correct the effects of phytoplankton vertical nonuniform distribution on remote sensing reflectance of cyanobacterial bloom waters

“…This hypothesis was accepted and used widely in research on vertically nonuniform waters (Mill an-N uñez et al 1997;Zaneveld et al 2005;Bresciani et al 2014). However, a common view concerning a reliable model for weighted mean pigment concentration detectable by remote sensors has not yet been achieved even for Case 1 waters (Sokoletsky and Yacobi 2011).…”