[29-Aug-2019] The Physical Oceanography Distributed Active Archive Center (PO.DAAC) is pleased to announce the release of the version 4.0 SMAP Sea Surface Salinity (SSS) data from Remote Sensing Systems (RSS). Enhancements over the previous release include:

• Improved land correction allows for salinity retrievals within 30 - 40km of the coast. The land correction uses a land correction table at 0.125 degree spatial resolution. The land emission that is used in the land correction is based on SMAP TB.
• Replacement of the previous NCEP sea-ice mask with one based on RSS AMSR-2 and implementation of a sea-ice threshold of 0.3% (gain weighted sea-ice fraction).
• Revised solar flagging that depends on glint angle and wind speed.
• Inclusion of estimated SSS-uncertainty in the L3 products.

Datasets comprising this release include Level 2C and L3 mapped monthly and 8-day running mean SMAP-SSS. All products are in the netCDF4 file format and are CF/ACDD metadata standards compliant. Note that unlike in prior releases, the 40-km and 70-km fields have been consolidated as variables within a single data product rather than being made available as distinct datasets. The 70-km data are based on a smoothing of the 40-km product, which is retrieved directly from the geophysical model function (Meissner et al. 2018). The 70-km version should be considered the official product with the 40-km included for experimental purposes. For most open ocean applications, the 70-km fields are the best used since they have significantly lower noise than the 40-km data. We also recommend the use of the V4.0 forward stream data over the prior version, which is deprecated and will be retired within the next 6 months. The RSS SMAP-SSS V4.0 datasets are described, discoverable, and accessible via the PO.DAAC data portal, as are the associated technical documentation. General information regarding the SMAP mission is available from the mission website and also via PO.DAAC's SMAP and salinity webpages. Meissner, T., F.J. Wentz, and D.M. Le Vine, 2019, The Salinity Retrieval Algorithms for the NASA Aquarius Version 5 and SMAP Version 3 Releases, Remote Sensing 10, 1121, doi:10.3390/rs10071121. Meissner, T., F. J. Wentz, A. Manaster, R. Lindsley, 2019: Remote Sensing Systems SMAP Ocean Surface Salinities [Level 2C, Level 3 Running 8-day, Level 3 Monthly], Version 4.0 validated release. Remote Sensing Systems, Santa Rosa, CA, USA. Available online at www.remss.com/missions/smap, 10.5067/SMP40-2SOCS, and 10.5067/SMP40-3SMCS. Please contact podaac@podaac.jpl.nasa.gov or visit the PO.DAAC Forum.