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S-NPP VIIRS Ocean Color science quality data -- striping issue?

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Anonymous, modified 4 Years ago.

S-NPP VIIRS Ocean Color science quality data -- striping issue?

Looking at this science quality Level-2 (Swath granule) V2019157205123_NPP_SCINIR_L2.nc  there appears to be striping (nLw 671) along the California coast.  Is this an issue with data quality?  I would think 'Science Quality'  would not contain these artifacts.

MS
Michael Soracco, modified 4 Years ago.

RE: S-NPP VIIRS Ocean Color science quality data -- striping issue?

Youngling Posts: 39 Join Date: 8/11/16 Recent Posts

This is related to data quality and when working with the S-NPP VIIRS ocean color Level-2 data,  there are two variables to assist in assessing the quality of a pixel/measurement:   /geophysical_data/qa_score and /geophysical_data/l2_flags. 

When looking at satellite oceanographic processing (especially optical instruments), many factors affect the calculation of a parameter.  In this case,  the observed striping occurs in an area of high glint.  The true color image below shows three areas of sun glint.  


[S-NPP VIIRS True Color  for 20190606  from NESDIS/STAR/SOCD/MECB]
 

[S-NPP VIIRS nLw (671) 20190606 unmasked]

 

By applying a mask  (the HIGLINT flag is contained in the l2_flags variable), you can show only the unaffected data.  

 


[S-NPP VIIRS nLw (671) 20190606 HIGLINT mask]  ​​​​

 

As recommended by the NOAA Ocean Color Science Team, NOAA CoastWatch applies multiple flags to only retain the highest quality data when processing from Level-2 to Level-3 (mapped) products:  ATMFAIL, LAND, HILT, HISATZEN, CLDSHDSTL, CLDICE, LOWLW, CHLFAIL, CHLWARN, NAVWARN, MAXAERITER, HISOLZEN, NAVFAIL, FILTER, HIGLINT.  Information on these flags can be found in the ATBD available on the product page 'Documentation' tab on the coastwatch.noaa.gov website.


S-NPP VIIRS nLw (671) with ATMFAIL, LAND, HILT, HISATZEN, CLDSHDSTL, CLDICE, LOWLW, CHLFAIL, CHLWARN, NAVWARN, MAXAERITER, HISOLZEN, NAVFAIL, FILTER, HIGLINT masked
 
The images above were screenshot from the CoastWatch Data Analysis Tool freely available from coastwatch.noaa.gov.
cdat level-2 ocean color flags data quality l2 flags data processing