Chlorophyll-a algorithm & sediment contamination

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cassandra21
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Chlorophyll-a algorithm & sediment contamination

by cassandra21 » Sat Nov 11, 2023 8:10 am America/New_York

Hii everyone,

I am analysing spatial patterns around an island in Cape Verde using MODIS-Aqua L2map satellite images. I have detected unusually high Chlor-a pixel values in the coastal regions compared to the rest of the image. This abnormality typically occurs in about 12 pixels out of the entire image.
I am curious to know if the Chlor-a algorithm is possibly identifying sediments.

Thank you!

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OB General Science - guoqingw
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Re: Chlorophyll-a algorithm & sediment contamination

by OB General Science - guoqingw » Thu Nov 30, 2023 12:04 pm America/New_York

Hi,

First of all, here is the theoretic basis for the standard Chlorophyll-a algorithm we use: https://oceancolor.gsfc.nasa.gov/resources/atbd/chlor_a/.
Second, yes, for coastal regions, the standard Chlorophyll-a values tend to be higher due to the optical complexity of the water. That said, the optical properties of colored dissolved organic and suspended particulate matters influence the blue and green bands of Rrs, thus the band ratio used in Chlorophyll-a algorithm. You may want to tune the algorithm parameters using in situ data from your region or seek a different algorithm to obtain satisfying results. If you want to do so, inside SeaDAS (https://seadas.gsfc.nasa.gov), there are a series of other algorithms you can choose to use to reprocess the satellite imagery for your region from L1B to L2.

Hope that helps,
Guoqing

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