RSS SMAP Level 3 Sea Surface Salinity Standard Mapped Image 8-Day Running Mean V5.0 Validated Dataset

1 Publication Cited this Dataset
Citation metrics available for years (2014-2022)
Processing Level3
Start/Stop Date2015-Mar-27 to Present
DescriptionThe version 5.0 SMAP-SSS level 3, 8-Day running mean gridded product is based on the fifth release of the validated standard mapped sea surface salinity (SSS) data from the NASA Soil Moisture Active Passive (SMAP) observatory, produced operationally by Remote Sensing Systems (RSS). The major changes in Version 5.0 from Version 4 are: (1) the addition of formal uncertainty estimates to all salinity retrieval products. (2) Sea-ice flagging and sea-ice side-lobe correction based on direct ingestion of AMSR-2 brightness temperature (TB) measurements. This is in contrast to Version 4 and earlier versions in which the sea-ice correction was based on an external sea-ice concentration product. The use of AMSR-2 TB measurements in the SMAP Version 5 products allows for salinity retrievals closer to the sea-ice edge and aids in the detection of large icebergs near the Antarctic. Daily data files for this product are based on SSS averages spanning an 8-day moving time window. SMAP data begins on April 1,2015 and is ongoing. L3 products are global in extent with a default spatial resolution of approximately 70KM. The datasets are gridded at 0.25degree x 0.25degree. 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.
Name: Soil Moisture Active and Passive Observatory (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: 2022-Feb-25

Keyword(s)RssSmapSSSv5, V5, L3, Level 3, 8 day running mean, SMAP, SMAP-SSS, Soil Moisture Active, Passive, salinity, polar, sun-synchronous, sss, sea surface, salinity, psu, NASA, project, mission, RSS, REMSS, Remote Sensing Systems
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Spatial Resolution: 0.25 Decimal Degrees x 0.25 Decimal Degrees
Temporal Resolution: Weekly - < Monthly
Region: GLOBAL
North Bounding Coordinate: 90 degrees
South Bounding Coordinate: -90 degrees
West Bounding Coordinate: -180 degrees
East Bounding Coordinate: 180 degrees
Time Span: 2015-Mar-27 to Present
Projection Type: Gridded
Ellipsoid: WGS 84
NameLong NameUnit
anc_sea_ice_flagancillary sea-ice detection indicator at center day1
flandaverage land fraction within 3dB contour1
gice_estestimated sea ice fraction weighted by antenna gain1
glandaverage land fraction weighted by antenna gain1
latcenter latitude of grid celldegrees_north
loncenter longitude of grid celldegrees_east
nobsNumber of observations for L3 average of SSS smoothed to approx 70km resolution1
nobs_40kmNumber of observations for L3 average of SSS at 40km resolution1
nobs_RFNumber of observations for L3 average of rain filtered SSS smoothed to approx 70km resolution1
sea_ice_zonessea-ice contamination zones at center day1
sss_refReference sea surface salinity from HYCOM1e-3
sss_smapSMAP sea surface salinity smoothed to approx 70km resolution1e-3
sss_smap_40kmSMAP sea surface salinity at original 40km resolution1e-3
sss_smap_40km_unctotal formal uncertainty estimate of SMAP sea surface salinity at original 40km resolution1e-3
sss_smap_40km_unc_compformal uncertainty components of SMAP sea surface salinity at original 40km resolution1e-3
sss_smap_RFRain filtered SMAP sea surface salinity smoothed to approx 70km resolution1e-3
sss_smap_RF_unctotal formal uncertainty estimate of rain filtered SMAP sea surface salinity smoothed to approx 70km resolution1e-3
sss_smap_unctotal formal uncertainty estimate of SMAP sea surface salinity smoothed to approx 70km resolution1e-3
sss_smap_unc_compformal uncertainty components of SMAP sea surface salinity smoothed to approx 70km resolution1e-3
surtepAncillary sea surface temperature (from CMC)Kelvin
timereference time of analyzed variable field corresponding to center of the product time intervalseconds since 2000-01-01T00:00:00Z
winspdAncillary sea surface wind speed from CCMP NRT that is used in surface roughness correctionm s-1
Citation is critically important for dataset documentation and discovery. Please cite the data as follows, and cite the reference papers when it is appropriate.
Citation Remote Sensing Systems (RSS). 2022. SMAP Sea Surface Salinity Products. Ver. 5.0. 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, 2018: Remote Sensing Sytems SMAP Ocean Surface Salinities, Version 4.0 validated release. Remote Sensing Systems, Santa Rosa, CA, USA.