Noticeable shift in select 4km global datasets

Update:  October 17, 2023

The cause of the shift in data appears to be due to a version change of an underlying mapping program. The following VIIRS products have been corrected:

• Global 4km Ocean Color S-NPP VIIRS (Science Quality)

  • Daily  (Chlorophyll-a, kd490, kdPAR, nLw[410,443,486,551,671,638ag])

  • Path: /pub0011/mecb/coastwatch/viirs/science/L3/global/

  • Example Filenames: V2023268_D1_WW00_nLw551.nc

• Global 4km Chlorophyll OCI S-NPP+NOAA-20 (NRT)

  • Path: /pub0016/coastwatch/mixed_viirs/L3/global/chlora/daily/WW00

  • Example Filename: V2023145_D1_NPP-N20_WW00_chloci.nc

• Global 4km Ocean Color IOP (NRT)

  • Path: /pub0011/mecb/coastwatch/viirs/nrt/L3/global/iop/daily/WW00

  • Example Filename: V2022365_D1_WW00_adg443.nc

• Global 4km Ocean Color S-NPP VIIRS (Science Quality)

  • Weekly, Monthly (Chlorophyll-a, kd490, kdPAR, nLw[410,443,486,551,671,638ag], PAR, SPM)

  • Path: /pub0011/mecb/coastwatch/viirs/science/L3/global/

  • Example Filenames: V2023225_2023231_D7_WW00_nLw410.nc

The datasets that continue to exhibit the issue will be reprocessed the week of October 16, 2023.  These datasets are:

• Global 4km Anomaly Ratio and Difference Products (NRT + Science Quality):

  • Path: /pub0011/mecb/coastwatch/viirs/nrt/L3/global/chlora/anom[_n20]/WW00

  • Example Filenames: V2021293_D1_NRT_WW00_chlorapdif.nc, V2021221_D1_NRT_WW00_chloradiff.nc

Please be aware NOAA CoastWatch has noted a positional shift in S-NPP/NOAA-20 VIIRS ocean color global mapped datasets.  We are investigating the cause within the processing chain and correction/re-processing that will be taken to resolve the issue.  The shift in data appears to be a systematic 2 pixel (9.3 km) westward shift in data pixels.  Although the shifted data predominantly occurs beginning June 29, 2022 (Day of Year 180) there are some interspersed reprocessed datasets pre-dating that date.

NOAA CoastWatch will reprocess the affected datasets and update this notice as more information is known (note,  during a Government shutdown,  updates will not be published but may occur. Please contact coastwatch.info@noaa.gov for information).

Datasets affected by this include:

• Global 4km Anomaly Ratio and Difference Products (NRT + Science Quality):

  • Path: /pub0011/mecb/coastwatch/viirs/nrt/L3/global/chlora/anom[_n20]/WW00

  • Example Filenames: V2021293_D1_NRT_WW00_chlorapdif.nc, V2021221_D1_NRT_WW00_chloradiff.nc

• Global 4km Chlorophyll OCI S-NPP+NOAA-20 (NRT)

  • Path: /pub0016/coastwatch/mixed_viirs/L3/global/chlora/daily/WW00

  • Example Filename: V2023145_D1_NPP-N20_WW00_chloci.nc

• Global 4km Ocean Color IOP (NRT)

  • Path: /pub0011/mecb/coastwatch/viirs/nrt/L3/global/iop/daily/WW00

  • Example Filename: V2022365_D1_WW00_adg443.nc

• Global 4km Ocean Color S-NPP VIIRS (Science Quality)

  • Daily, Weekly, and Monthly (Chlorophyll-a, kd490, kdPAR, nLw[410,443,486,551,671,638ag], PAR, SPM)

  • Path: /pub0011/mecb/coastwatch/viirs/science/L3/global/

  • Example Filenames: V2023049_D1_WW00_chlora.nc, V2022213_2022243_F31_WW00_chlora.nc