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Description

This is the PI-produced JPL SMAP-SSS V5.0 CAP, level 3, monthly mapped sea surface salinity (SSS) product from the NASA Soil Moisture Active Passive (SMAP) observatory. It is based on the Combined Active-Passive (CAP) retrieval algorithm developed at JPL originally in the context of Aquarius/SAC-D and now extended to SMAP. JPL SMAP V5.0 SSS is based on the newly released SMAP V5 Level-1 Brightness Temperatures (TB). An enhanced calibration methodology has been applied to the brightness temperatures, which improves absolute radiometric calibration and reduces the biases between ascending and descending passes. The improved SMAP TB Level 1 TB will enhance the use of SMAP Level-1 data for other applications, such as sea surface salinity and winds. L3 monthly product file variables include: derived SSS with associated uncertainties and wind speed from SMAP and ancillary surface salinity from HYCOM. SMAP data begins on April 1, 2015 and is ongoing, with a 1 month latency in processing and availability. L3 products are global in extent and gridded at 0.25degree x 0.25degree with an approximate spatial resolution of 60km. 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 for the surface roughness correction required for the surface salinity retrieval.

Product Summary

Platforms
SMAP
Instruments
SMAP L-BAND RADIOMETER
Spatial Extent

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

Spatial Resolution
0.6 Decimal Degrees x 0.6 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
C2208423975-POCLOUD
Data State
ACTIVE
Number of Files/Granules
104
Processing Level
3
Published
Updated
Science Keywords
Surface Winds ,
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

NASA/JPL. (2020). JPL SMAP Level 3 CAP Sea Surface Salinity Standard Mapped Image Monthly V5.0 Validated Dataset [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/SMP50-3TMCS 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
anc_sss HYCOM sea surface salinity 1e-3 float -9999 0 to 45 1
anc_sst Sea surface temperature K float -9999 0 to 340 1
ice_fraction Average ice fraction N/A float -9999 0 to 1 1
land_fraction Average land fraction N/A float -9999 0 to 1 1
latitude latitude of grid cell degrees_north float N/A N/A 1
longitude longitude of grid cell degrees_east float N/A N/A 1
smap_high_spd SMAP 10 m wind speed (using ancillary SSS) m s-1 float -9999 0 to 100 1
smap_spd SMAP 10 m wind speed m s-1 float -9999 0 to 100 1
smap_sss SMAP sea surface salinity 1e-3 float -9999 0 to 45 1
smap_sss_uncertainty SMAP SSS uncertainty 1e-3 float -9999 0 to 50 1
time Midpoint of time interval of analyzed fields seconds since 2015-1-1 00:00:00 UTC float -9999 N/A 1
weight Sum of Gaussian weighting factors N/A float N/A N/A 1
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