Negative values in QAA products

[zxqwss]

Dear Sir or Madam,

I am working with Ocean Level-3 Standard Mapped Image Products to derive IOPs using QAA-v6. However, I encountered many negative anw values over open water, especially with wavelength>600 nm. Is there any suggestion how to proceed with these negative values?

Kind Regards,

Heidi

[lmckinna]

Hi Heidi,

To help me understand a little better, can you please advise which L3 files you are seeing negative values in? You will see missing data (that may appear as negative values when loaded) on daily L3 products where data are masked out due to land, clouds, ice, sunglint contamination, and orbit gaps. As the temporal aggregation of the L3 file increases (i.e., weekly, monthly, seasonally) missing data will get filled in.

Also, OB.DAAC standard L3 IOP products are generated with GIOP. How are you producing/accessing QAA-based IOPs?

Lachlan

[zxqwss]

Hi Lachlan,

Thank you very much for your reply! I am sorry for this confusion. To clarify, my issue is not with negative values in L3 IOP products, but rather with results from my own QAA derivation using L3 Rrs products. Specifically, the total minus water absorption coefficient (anw) derived through this method frequently shows many negative values in open water (wavelength>600 nm). But I find the standard L3 IOP products generated with GIOP exhibit far fewer such anomalies, so I want to know if there is any solution to mitigate this negative values?

Heidi

[lmckinna]

Hi Heidi,

Thanks for clarifying. It sounds like the issue lies in the QAA code that you have developed separate to OCSSW. Unfortunately, I can't provide specific assistance on individual IOP code implementations.

Lachlan

[zxqwss]

Hi Lachlan,

OK, I will continue exploring other methods. In any case, thank you for your reply.

Heidi.