Friday, July 27, 2018

The Physical Oceanography Distributed Active Archive Center (PO.DAAC) is pleased to announce the availability of the Level 4 optimally interpolated, 0.5 degree, near-global, 7-day sea surface salinity (OISSS) product for version 5.0 of the Aquarius/SAC-D dataset.  OISSS is a principal investigator produced dataset developed at the International Pacific Research Center (IPRC) of the University of Hawaii at Manoa, School of Ocean and Earth Science and Technology (SOEST).  The optimal interpolation (OI) mapping procedure used to create this product corrects for systematic spatial biases in Aquarius SSS data with respect to in-situ near-surface salinity observations and takes into account available statistical information about the signal and noise, specific to the Aquarius instrument.  The product covers the entire duration of the Aquarius/SAC-D mission:  8/26/2011 – 6/7/2015. Enhancements for this new version of the OISSS product based on V5.0 Aquarius level 2 swath data include: 1) Improved estimates of the first guess based on the average of four different in-situ based SSS products. 2) Improved selection of input data, including the use of extended satellite data quality flagging. 3) The bias correction algorithm has been updated to adjust SSS retrievals for large-scale systematic biases on a repeat-track basis. 4) Less restrictive thresholds are implemented to filter observations for land and ice contamination, thus improving coverage in the coastal areas and semi-enclosed seas.  The summary of changes for the new version of OISSS product, including the validation statistics, can be found in: Melnichenko, O., and P. Hacker (2018), Summary of Changes to “Aquarius sea surface salinity optimal interpolation analysis”, IPRC Technical Note No.7, 26 June 2018.   Further details on the data processing can be found in: Melnichenko, O., P. Hacker., N. Maximenko, G. Lagerloef, and J. Potemra (2016), Optimal interpolation of Aquarius sea surface salinity, J. Geophys. Res. Oceans, 121, 602-616, doi:10.1002/2015JC011343.

The OISSS product is described and discoverable via the PO.DAAC data portal.   Access to these data is via PO.DAAC’s public FTP but preferentially via PODAAC Drive going forward given deprecation of PO.DAAC’s public FTP site.  The data are also available via OPeNDAP, PODAAC-WS, THREDDS and LAS.

Documentation and a publication on the OISSS product are available from the PO.DAAC FTP site with associated reader software.   General information regarding Aquarius/SAC-D mission is available from the mission website and also via PO.DAAC’s Aquarius  and salinity webpages.

Questions may be addressed to: or the PO.DAAC Salinity Forum.