Skip to main content

Description

The RSS SMAP Level 3 Sea Surface Salinity Standard Mapped Image 8-Day Running Mean V6.0 Validated 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 RSS SMAP 8-Day running mean product is based on SSS averages spanning an 8-day moving time window, it includes data for a range of parameters: derived sea surface salinity (SSS) with SSS-uncertainty, rain filtered SMAP sea surface salinity, collocated wind speed, data and ancillary reference surface salinity data from HYCOM.
Each data file is available in netCDF-4 file format with about 7-day latency (after the end of the averaging period).
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
0.25 Decimal Degrees x 0.25 Decimal Degrees
Location
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2015-03-27
Data Partner
Remote Sensing Systems (RSS) ,
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC)
Concept ID
C2832227567-POCLOUD
Data State
ACTIVE
Number of Files/Granules
3938
Processing Level
3
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 3 Sea Surface Salinity Standard Mapped Image 8-Day Running Mean V6.0 Validated Dataset [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/SMP60-3SPCS Date Accessed: 2026-04-21

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
anc_sea_ice_flag ancillary sea-ice detection indicator at center day 1 byte N/A N/A 1 N/A
fland average land fraction within 3dB contour 1 float -9999 0 to 1 1 N/A
gice_est estimated sea ice fraction weighted by antenna gain 1 float -9999 0 to 1 1 N/A
gland average land fraction weighted by antenna gain 1 float -9999 0 to 1 1 N/A
lat center latitude of grid cell degrees_north float N/A -90 to 90 1 N/A
lon center longitude of grid cell degrees_east float N/A 0 to 360 1 N/A
nobs Number of observations for L3 average of SSS smoothed to approx 70km resolution 1 int 0 1 to 480 1 N/A
nobs_40km Number of observations for L3 average of SSS at 40km resolution 1 int 0 1 to 480 1 N/A
nobs_RF Number of observations for L3 average of rain filtered SSS smoothed to approx 70km resolution 1 int 0 1 to 480 1 N/A
sea_ice_zones sea-ice contamination zones at center day 1 byte N/A N/A 1 N/A
sss_ref Reference sea surface salinity from HYCOM 1e-3 float -9999 0 to 45 1 N/A
sss_smap SMAP sea surface salinity smoothed to approx 70km resolution 1e-3 float -9999 0 to 45 1 N/A
sss_smap_40km SMAP sea surface salinity at original 40km resolution 1e-3 float -9999 0 to 45 1 N/A
sss_smap_40km_unc total formal uncertainty estimate of SMAP sea surface salinity at original 40km resolution 1e-3 float -9999 0 to 45 1 N/A
sss_smap_40km_unc_comp formal uncertainty components of SMAP sea surface salinity at original 40km resolution 1e-3 float -9999 0 to 45 1 N/A
sss_smap_RF Rain filtered SMAP sea surface salinity smoothed to approx 70km resolution 1e-3 float -9999 0 to 45 1 N/A
sss_smap_RF_unc total formal uncertainty estimate of rain filtered SMAP sea surface salinity smoothed to approx 70km resolution 1e-3 float -9999 0 to 45 1 N/A
sss_smap_unc total formal uncertainty estimate of SMAP sea surface salinity smoothed to approx 70km resolution 1e-3 float -9999 0 to 45 1 N/A
sss_smap_unc_comp formal uncertainty components of SMAP sea surface salinity smoothed to approx 70km resolution 1e-3 float -9999 0 to 45 1 N/A
surtep Ancillary sea surface temperature (from CMC) Kelvin float -9999 0 to 313.15 1 N/A
time reference time of analyzed variable field corresponding to center of the product time interval seconds since 2000-01-01T00:00:00Z double N/A N/A 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
You're viewing 22 of 22