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Description

The RSS SMAP level 2C sea surface salinity V6.0 dataset produced by the Remote Sensing Systems (RSS) and sponsored by the NASA Ocean Salinity Science Team, is a validated product that provides orbital/swath data on sea surface salinity (SSS) derived from the NASA's Soil Moisture Active Passive (SMAP) mission. The SMAP satellite was launched on 31 January 2015
with 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. 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.

The major changes in Version 6.0 from Version 5.0 are: (1) Removal of biases during the first few months of the SMAP mission that are related to the operation of the SMAP radar during that time. (2) Mitigation of biases that depend on the SMAP look angle. (3) Mitigation of salty biases at high Northern latitudes. (4) Revised sun-glint flag.
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), is available in netCDF-4 file format with about 4 days latency.
Data begins on April 1,2015 and is ongoing. Observations are global in extent with an approximate spatial resolution of 40KM. Note that while a SSS 40KM variable is also included in the product for most open ocean applications, The standard product of the SMAP Version 6.0 release is the smoothed salinity product with a spatial resolution of approximately 70 km.
This activity was informed by the Satellite Needs Working Group (SNWG), an interagency effort of the U.S. Government dedicated to identifying and addressing Earth observation needs across U.S. civilian federal agencies.

Product Summary

Platforms
SMAP
Instruments
SMAP L-BAND RADIOMETER
Spatial Extent

N: 90 S: -90 E: 180 W: -180

Spatial Resolution
47000 Meters x 39000 Meters
Location
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2015-04-01
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC)
Concept ID
C2832221740-POCLOUD
Data State
ACTIVE
Number of Files/Granules
48590
Processing Level
2
Published
Updated
Science Keywords
Salinity

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

Remote Sensing Systems. (2024). RSS SMAP Level 2C Sea Surface Salinity V6.0 Validated Dataset [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/SMP60-2SOCS Date Accessed: 2026-05-28

Documents

Variables

The table below lists the variables contained within a single granule for this dataset. Variables often contain observed or derived geophysical measurements collected from a variety of sources, including remote sensing instruments on satellite and airborne platforms, field campaigns, in situ measurements, and model outputs. The terms variable, parameter, scientific data set, layer, and band have been used across NASA’s Earth science disciplines; however, variable is the designated nomenclature in NASA’s Common Metadata Repository (CMR). Variable metadata attributes such as Name, Description, Units, Data Type, Fill Value, Valid Range, and Scale Factor allow users to efficiently process and analyze the data. The full range of attributes may not be applicable to all variables. Additional information on variable attributes is typically available in the data, user guide, and/or other product documentation.

For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor Offset
tb_toi Brightness temperature at top of ionosphere. Pol basis V,H,S3,S4 Kelvin float -9999 0 to 330 1 N/A
TEC Vertically integrated electron content between surface and S/C 1e16 m-2 float -9999 N/A 1 N/A
temp_ant Physical temperature of reflector from L1B files. Pol basis V,H Kelvin float -9999 N/A 1 N/A
time Time of observation seconds since 2000-1-1 0:0:0 0 double N/A N/A 1 N/A
tran Total atmospheric transmittance 1 float -9999 0 to 1 1 N/A
windir Ancillary wind direction relative to North (from NCEP, meteorological convention) that is used in surface roughness correction degree float -9999 0 to 360 1 N/A
winspd Ancillary sea surface wind speed from CCMP NRT that is used in surface roughness correction m s-1 float -9999 0 to 100 1 N/A
zang Orbital position angle of S/C. 0 is South. 90 is equator ascending. 180 is North. 270 is equator descending. degree float -9999 0 to 360 1 N/A
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