Bio-optical characterization of the Salish Sea, Canada towards improved chlorophyll algorithms for MODIS and Sentinel-3
Presentation Abstract
Measured in situ biogeochemcial and optical measurements, acquired at 145 stations, showed considerable variation; chlorophyll a (Chla) (mean=1.64, range: 0.10 – 7.20 µg.l-1), total suspended matter (TSM) (3.09, 0.82 – 20.69 mg.l-1), and absorption by chromophoric dissolved organic matter () (0.525, 0.007 – 3.072 m-1), thus representing the spatial and temporal variability of the Salish Sea. Optically, a comparable range was found; particulate scattering () (1.316, 0.250 – 7.450 m-1), particulate backscattering () (0.022, 0.005 – 0.097 m-1), and particulate absorption coefficient () (0.345, 0.048 – 2.020 m-1). Empirical orthogonal function (EOF) analysis revealed 95% of remote sensing reflectance (Rrs) variance was highly correlated to (r = 0.90), (r = 0.82) and TSM concentration (r = 0.80). Hierarchical clustering on normalized Rrs revealed two dominant classes, (1) estuarine class, (2) oceanic class. Estuarine waters were defined by high overall Rrs magnitudes in the red, indicating more turbid waters, and well defined fluorescence and absorption features, indicated a high Chla and TSM presence. Oceanic waters showed low TSM influence and more ranging Chla presence suggesting more optically clear oceanic waters. In situ Chla and Rrs measurements, were then used to parameterize the OC3M/OC3S3, two-band ratio, FLH and modified FLH (ModFLH) empirical algorithms. A systematic overestimation of low Chla concentrations and underestimation of higher Chla values for all four algorithms was observed when tuned to regional data. Algorithm accuracy was significantly improved for the class-specific parametrizations with the two-band ratio showing a strong correlation to the Chla concentrations in the estuarine class (R2 ~ 0.71; RMSE ~ 0.33) and the ModFLH algorithm in the oceanic class (R2 ~ 0.70; RMSE ~ 0.26). These results demonstrated the benefit of applying an optical classification as a necessary first step into improving Chla retrievals from remotely sensed data in the contrasted coastal waters of the Salish Sea.
Session Title
Remote sensing technology to monitor the short and long term dynamic of the Salish Sea
Conference Track
Habitat
Conference Name
Salish Sea Ecosystem Conference (2016 : Vancouver, B.C.)
Document Type
Event
Start Date
2016 12:00 AM
End Date
2016 12:00 AM
Location
2016SSEC
Type of Presentation
Oral
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Environmental monitoring--Salish Sea (B.C. and Wash.); Optical measurements--Salish Sea (B.C. and Wash.)
Geographic Coverage
Salish Sea (B.C. and Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Bio-optical characterization of the Salish Sea, Canada towards improved chlorophyll algorithms for MODIS and Sentinel-3
2016SSEC
Measured in situ biogeochemcial and optical measurements, acquired at 145 stations, showed considerable variation; chlorophyll a (Chla) (mean=1.64, range: 0.10 – 7.20 µg.l-1), total suspended matter (TSM) (3.09, 0.82 – 20.69 mg.l-1), and absorption by chromophoric dissolved organic matter () (0.525, 0.007 – 3.072 m-1), thus representing the spatial and temporal variability of the Salish Sea. Optically, a comparable range was found; particulate scattering () (1.316, 0.250 – 7.450 m-1), particulate backscattering () (0.022, 0.005 – 0.097 m-1), and particulate absorption coefficient () (0.345, 0.048 – 2.020 m-1). Empirical orthogonal function (EOF) analysis revealed 95% of remote sensing reflectance (Rrs) variance was highly correlated to (r = 0.90), (r = 0.82) and TSM concentration (r = 0.80). Hierarchical clustering on normalized Rrs revealed two dominant classes, (1) estuarine class, (2) oceanic class. Estuarine waters were defined by high overall Rrs magnitudes in the red, indicating more turbid waters, and well defined fluorescence and absorption features, indicated a high Chla and TSM presence. Oceanic waters showed low TSM influence and more ranging Chla presence suggesting more optically clear oceanic waters. In situ Chla and Rrs measurements, were then used to parameterize the OC3M/OC3S3, two-band ratio, FLH and modified FLH (ModFLH) empirical algorithms. A systematic overestimation of low Chla concentrations and underestimation of higher Chla values for all four algorithms was observed when tuned to regional data. Algorithm accuracy was significantly improved for the class-specific parametrizations with the two-band ratio showing a strong correlation to the Chla concentrations in the estuarine class (R2 ~ 0.71; RMSE ~ 0.33) and the ModFLH algorithm in the oceanic class (R2 ~ 0.70; RMSE ~ 0.26). These results demonstrated the benefit of applying an optical classification as a necessary first step into improving Chla retrievals from remotely sensed data in the contrasted coastal waters of the Salish Sea.
