Monday, November 5, 2018

The PO.DAAC is pleased to announce the availability of the version 3.0 SMAP Sea Surface Salinity (SSS) data from Remote Sensing Systems (RSS).  Several enhancements over the previous release are implemented including:

  • Use of Version 4 L1B SMAP RFI filtered antenna temperatures.
  • Implementation of the geophysical model function from Aquarius version 5 adapted to SMAP.
  • Use of the near real time CCMP wind speed and direction data as ancillary input.
  • Inclusion of IMERG rain rate for the atmospheric liquid cloud water correction and rain flagging.
  • Improved computation of antenna weighted land fraction (gland) and enhanced correction for land radiation intrusion from antenna sidelobes.
  • Improved correction for emissive SMAP mesh antenna.
  • The salty biases at low latitudes and the fresh biases at high N latitudes that were observed in the previous release, are no longer present or are much reduced in V3.0.

Users should note that significant degradation in the performance is observed if the gain weighted land fraction (gland) exceeds 1%. Consequently, observations with gland>0.8% are not used in the Level 3 processing.

Datasets comprising this release include 40km and 70km resolution products at level 2C and 3. L3 mapped salinity products consist of an 8-day running mean product based on the repeat orbit of the SMAP mission, along with a monthly average product.  All products are in the netCDF4 file format and are CF/ACDD metadata standards compliant.

For most open ocean applications, the 70-km products are the best to use as they have significantly lower noise than the 40-km products.

The SMAP-SSS V3.0 datasets are described and discoverable via the PO.DAAC data portal.   Access to these data is via PO.DAAC’s public FTP site (Level 2  and Level 3 mapped) but preferentially via PODAAC Drive (Level 2  and Level 3 mapped) going forward given deprecation of PO.DAAC’s public FTP site.  The data are also accessible via a range of PO.DAAC tools and services: OPENDAP (Level 2 and Level 3 mapped), THREDDS, PODAAC-WS and LAS.

The SMAP Algorithm Theoretical Basis Document (ATBD), validation analysis and file specification document together with other primary technical documentation, are available from the FTP site together with reader software. General information regarding the SMAP mission is available from the mission website  and also via PO.DAAC’s SMAP and salinity webpages.

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



Important Information for Users:

NASA is in the process of deprecating the use of the FTP protocol for data and information access. PO.DAAC is pleased to offer PO.DAAC Drive as a robust FTP alternative for browsing and retrieving data at PO.DAAC (  It offers file navigation and download through an interface served directly through your browser, and with a familiar look and feel.  It also allows users to access data via a command line so that interactions can be easily scripted.