Abstract
Evaluation of MODIS-Aqua and OLCI Chlorophyll-a products in contrasting waters of the Southwestern Atlantic Ocean
Highlights
The objective of the present study is to test, for the first time in this optically complex area, using multiple atmospheric corrections and algorithms, several different Chl-a products derived from the Moderate Resolution Imaging Spectroradiometer on board Aqua (MODISAqua) and the Ocean and Land Color Instrument on board Sentinel 3 (OLCI-Sentinel 3) using in situ Chl-a
Even though the slope is close to 1, large errors indicate a poor performance of the algorithm with high scatter (RMSE = 1.65, percentage error (PE) = 118 %) and a clear tendency to overestimate in situ data, as indicated by the bias (1.18). This result is expected as more than half of the samples were collected within the coastal zone (z < 15 m; N=23; R2 = 0.21, red symbols in Figure 2A), characterized by turbid waters (Delgado et al, 2017; 2019), where Chl-a empirical algorithms usually tend to fail (OReilly et al, 2000)
The atmospheric correction (AC) performance could not be evaluated at this study due to the lack of radiometric measurements; based on previous results (Delgado et al, 2019), showing good performances in offshore waters and high errors in coastal waters, we can infer that AC is not a major issue
Summary
The objective of the present study is to test, for the first time in this optically complex area, using multiple atmospheric corrections and algorithms, several different Chl-a products derived from the Moderate Resolution Imaging Spectroradiometer on board Aqua (MODISAqua) and the Ocean and Land Color Instrument on board Sentinel 3 (OLCI-Sentinel 3) using in situ Chl-a.
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