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Description

The RSS SMAP Level 3 Sea Surface Salinity Standard Mapped Image Monthly 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.
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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 L3 monthly product 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 and is averaged over one-month time intervals 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.

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
Geographic Region
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
C2832226365-POCLOUD
Data State
ACTIVE
Number of Files/Granules
127
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 Monthly V6.0 Validated Dataset [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/SMP60-3SMCS Date Accessed: 2025-12-14

Documents

Variables

Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.

The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
fland average land fraction within 3dB contour 1 float -9999 0 to 1 1
gice_est estimated sea ice fraction weighted by antenna gain 1 float -9999 0 to 1 1
gland average land fraction weighted by antenna gain 1 float -9999 0 to 1 1
lat center latitude of grid cell degrees_north float N/A -90 to 90 1
lon center longitude of grid cell degrees_east float N/A 0 to 360 1
nobs Number of observations for L3 average of SSS smoothed to approx 70km resolution 1 int 0 1 to 480 1
nobs_40km Number of observations for L3 average of SSS at 40km resolution 1 int 0 1 to 480 1
nobs_RF Number of observations for L3 average of rain filtered SSS smoothed to approx 70km resolution 1 int 0 1 to 480 1
sss_ref Reference sea surface salinity from HYCOM 1e-3 float -9999 0 to 45 1
sss_smap SMAP sea surface salinity smoothed to approx 70km resolution 1e-3 float -9999 0 to 45 1
sss_smap_40km SMAP sea surface salinity at original 40km resolution 1e-3 float -9999 0 to 45 1
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
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
sss_smap_RF Rain filtered SMAP sea surface salinity smoothed to approx 70km resolution 1e-3 float -9999 0 to 45 1
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
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
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
surtep Ancillary sea surface temperature (from CMC) Kelvin float -9999 0 to 313.15 1
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
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
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