Topic: Change to processing standard of Jason-3 data

Date Issued: Issued October 27, 2020 2112Z

Product(s) or Data Impacted: Jason-3 Operational Geophysical Data Records (OGDRs)

Date/Time of Initial Impact: October 28, 2020 2102Z

Date/Time of Expected End: N/A

Length of Event: N/A

Details/Specifics of Change: This is a reminder that Jason-3 altimeter products generated by NOAA and EUMETSAT will be updated to the new GDR-F standard starting tomorrow October 28, 2020.

Since the launch of Jason-3, the GDR-D altimetry product standard has been used to process Jason-3 data. GDR-D will be replaced by the new GDR-F standard starting with FCDAS pass @21:02Z on October 28, 2020. This new standard will also be used to process the future Sentinel-6 Michael Freilich data (a.k.a. Jason-CS), thus facilitating multi-mission cross-calibration activities.

The upgrade to the new GDR-F standard will mostly affect the netCDF products, and will include the following changes (non-exhaustive list):

•   Improved algorithms for product generation and calibration
•   New quality flags added
•   Fix to known anomalies
•   Use of WGS84 instead of Jason-1 ellipsoid
•   New product fields added, like distance to the coast
•   Introduction of the netCDF version 4 format and compression for the output products
•   Some variable names modified

For the BUFR product, which is generated from the netCDF product,certain variables (those that will be removed in the GDR-F netCDF product) will be left empty after the change. The format of the BUFR product remains unchanged.

Full details on the changes are in updated versions of the Jason-3 Products Handbook and Jason-3 Products Specification document.

Filenames will also change to reflect the new standard. The letter representing the version will change from “d” to “f”.

Example for the netCDF products:

netCDF OGDR:

Current filename: JA3_OPN_2PdS168_068_20200901_231031_20200902_010647.nc.bz2
New filename: JA3_OPN_2PfS168_068_20200901_231031_20200902_010647.nc.bz2

netCDF OGDR-SSHA:

Current filename: JA3_OPR_2PdS168_068_20200901_231031_20200902_010647.nc.bz2
New filename: JA3_OPR_2PfS168_068_20200901_231031_20200902_010647.nc.bz2

Example for the NOAA BUFR product:
Current filename: W_US-NOAA-Washington,SURFACE+SATELLITE,JASON3+OGDR_C_KNES_20200904112950_d_168_129_20200904110819.
New filename: W_US-NOAA-Washington,SURFACE+SATELLITE,JASON3+OGDR_C_KNES_20200904112950_f_168_129_20200904110819.

Sample files, in both netCDF and BUFR formats, generated with the new standard, will be made available shortly.

Contact Information for Further Information: David Donahue - Satellite Services Division, NOAA/NESDIS/OSPO/SPSD/SPB, (301) 683-3236 David.R.Donahue@noaa.gov

Web Site(s) for applicable information: N/A

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