aerosol reflectance percentile of '1'

[cio]

Hi Quinten,

Wondering why the fixed aerosol reflectance is only recommended for sub scenes?

Also, I used an aerosol reflectance percentile of 1 for an image (whole S2 scene) and saw that this setting gives me expected Rrs values in the green band for my image area (low chlorophyll, winter image). Using the default value of 50 yields Rrs underestimation. So, what does using a value of 1' typically imply please?

Regards , C.

[quinten]

The aerosol percentile option extracts the given percentile from the histogram of reflectances (truncated by the "non-water" mask) in two bands (SWIR1 and SWIR2 by default). This value is then used as the aerosol reflectance and epsilon (the ratio of the reflectances) for the extrapolation. A higher percentile will then of course give a higher estimate for the aerosol reflectance (and in your case for example gives underestimated Rrs).

Fixing the aerosol reflectance assumes there is no or limited variability in aerosol concentration for your scene or subscene, and hence why I recommend it generally only for subscenes. Fixing it over the whole tile could work fine for your specific region for example.

[cio]

Thanks for this detailed explanation, Quinten!