RSS SMAP Level 2C Sea Surface Salinity V4.0 Validated Dataset
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Citation metrics available for years (2015-2019)
Short NameSMAP_RSS_L2_SSS_V4
DescriptionThe version 4.0 SMAP-SSS, level 2C product contains the fourth release of the validated sea surface salinity orbital/swath data from the NASA Soil Moisture Active Passive (SMAP) observatory, and is produced operationally by Remote Sensing Systems (RSS). Enhancements with this release include: use of an improved 0.125 degree land correction table with land emission based on SMAP TB; replacement of the previous NCEP sea-ice mask with one based on RSS AMSR-2 and implementing 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; consolidation of both 40KM and 70KM SMAP-SSS datasets as variable fields in a single data product. The SMAP-SSS L2C product includes data for a range of parameters: derived sea surface salinity (SSS) with SSS-uncertainty, brightness temperatures for each radiometer polarization, antenna temperatures, collocated wind speed, data and ancillary reference surface salinity data from HYCOM, rain rate, quality flags, and navigation data. Each data file covers one 98-minute orbit (15 files per day). Data begins on April 1,2015 and is ongoing. Observations are global in extent and provided at a 0.25 degree x 0.25 degree grid with an approximate spatial feature resolution of 40KM. Note that while a SSS 40KM variable is also included in the product, for most open ocean applications, the default SSS variable (70KM) is best used as they are significantly less noisy than the 40KM data.The SMAP satellite is in a near-polar orbit at an inclination of 98 degrees and an altitude of 685 km. It has an ascending node time of 6 pm and is sun-synchronous. With its 1000km swath, SMAP achieves global coverage in approximately 3 days, but has an exact orbit repeat cycle of 8 days. On board Instruments include a highly sensitive L-band radiometer operating at 1.41GHz and an L-band 1.26GHz radar sensor providing complementary active and passive sensing capabilities. Malfunction of the SMAP scatterometer on 7 July, 2015, has necessitated the use of collocated wind speed, primarily from WindSat, for the surface roughness correction required for the surface salinity retrieval.
Dataset TypeACTIVE
Processing Level2C
CoverageRegion: GLOBAL
North Bounding Coordinate: 90 degrees
South Bounding Coordinate: -90 degrees
West Bounding Coordinate: -180 degrees
East Bounding Coordinate: 180 degrees
Time Span: 2015-Apr-01 to Present
Granule Time Span: 2015-Apr-01 to 2021-Apr-03
ResolutionSpatial Resolution: 39 km (Along) x 47 km (Across)
ProjectionProjection Type: Swath
Ellipsoid: WGS 84
Swath Width1000 km
Name: NASA Soil Moisture Active Passive (SMAP) (SMAP)
Orbit Period: 98.5 minutes
Inclination Angle: 98.0 degrees
Swath Width: 1000.0 kilometers
Description: Spacecraft angular distance from orbital plane relative to the Equator.

ProjectSoil Moisture Active Passive (SMAP)
Data ProviderPublisher: Remote Sensing Systems (RSS)
Creator: Remote Sensing Systems (RSS)
Release Place: Remote Sensing Systems, 444 Tenth Street, Suite 200, Santa Rosa, CA 95401, USA
Release Date: 2019-Aug-28

Keyword(s)RssSmapSSSv4, V4, SMAP, SMAP-SSS, Soil Moisture Active Passive, salinity, polar, sun-synchronous, sss, psu, NASA, project, mission, RSS, Remote Sensing System, REMSS
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Citation Remote Sensing Systems (RSS). 2019. SMAP Sea Surface Salinity Products. Ver. 4.0. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at

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For more information see Data Citations and Acknowledgments.

Journal Reference Meissner, T. and F. J. Wentz, 2019: Remote Sensing Sytems SMAP Ocean Surface Salinities, Version 4.0 validated release. Remote Sensing Systems, Santa Rosa, CA, USA.
VersionDatasetVersion DateStatus
4.0RSS SMAP Level 2C Sea Surface Salinity V4.0 Validated Dataset2019-05-06ACTIVE1557186367715
3.0RSS SMAP Level 2 Sea Surface Salinity V3.0 40km Validated Dataset2018-08-23RETIRED1535043667680
2.0RSS SMAP Level 2C Sea Surface Salinity V2.0 Validated Dataset2016-10-22RETIRED1477095281797