JPL SMAP Level 2B Near Real-time CAP Sea Surface Salinity V5.0 Validated Dataset (2 hour latency)

Processing Level2
Start/Stop Date2015-Apr-01 to Present
DescriptionThe SMAP-SSS V5.0, level 2B (NRT CAP) dataset produced by the Jet Propulsion Laboratory Combined Active-Passive (CAP) project , is a validated product that provides near real-time orbital/swath data on sea surface salinity (SSS) and extreme winds, derived from the NASA's Soil Moisture Active Passive (SMAP) mission launched on January 31, 2015. This mission, initially designed to measure and map Earth's soil moisture and freeze/thaw state to better understand terrestrial water, carbon and energy cycles has been adapted to measure ocean SSS and ocean wind speed using its passive microwave instrument. The SMAP instrument is in a near polar orbiting, sun synchronous orbit with a nominal 8 day repeat cycle.

The dataset includes derived SMAP SSS, SSS uncertainty, wind speed and direction data for extreme winds, as well as brightness temperatures for each radiometer polarization. Furthermore, it contains ancillary reference surface salinity, ice concentration, wind and wave height data, quality flags, and navigation data. This broad range of parameters stems from the observatory's version 5.0 (V5) CAP retrieval algorithm, initially developed for the Aquarius/SAC-D mission and subsequently extended to SMAP. Datafrom April 1, 2015 to present, is available with a latency of about 6 hours. The observations are global, provided on a 25km swath grid with an approximate spatial resolution of 60 km. Each data file covers one 98-minute orbit, with 15 files generated per day. The data are based on the near-real-time SMAP V5 Level-1 Brightness Temperatures (TB) and benefits from an enhanced calibration methodology, which improves the absolute radiometric calibration and minimizes biases between ascending and descending passes. These improvements also enrich the applicability of SMAP Level-1 data for other uses, such as further sea surface salinity and wind assessments. Due to a malfunction of the SMAP scatterometer on July 7, 2015, collocated wind speed data has been utilized for the necessary surface roughness correction for salinity retrieval.

This JPL SMAP-SSS V5.0 dataset holds tremendous potential for scientific research and various applications. Given the SMAP satellite's near-polar orbit and sun-synchronous nature, it achieves global coverage in approximately three days , enabling researchers to monitor and model global oceanic and climatic phenomena with unprecedented detail and timeliness. These data can inform and enhance understanding of global weather patterns, the Earth’s hydrological cycle, ocean circulation, and climate change.
Swath Width1000 km
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: JPL
Creator: JPL
Release Place: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA91109, USA
Release Date: 2023-Jun-09

Keyword(s)JPLSMAPSSSV50, SMAP, SMAP-SSS, Soil Moisture Active Passive, salinity, polar, sun-synchronous, sss, psu, NASA, project, mission, JPL, CAP, combined active/passive, L2B, NRT, near real-time
Questions related to this dataset? Contact
Spatial Resolution: 25000 Meters x 25000 Meters
Temporal Resolution: Hourly - < Daily
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-Apr-01 to Present
Granule Time Span: 2022-Jan-13 to 2024-May-29
Swath Width: 1000 km
Projection Type: Swath
Ellipsoid: WGS 84
NameLong NameUnit
anc_dirNCEP wind direction (oceanographic convention)Degrees
anc_spd10 meter NCEP wind speed (scaled by 1.03)Meters/second
anc_sssHYCOM salinityPSU
anc_sstNOAA Optimum Interpolation sea surface temperatureDegrees kelvin
anc_swhNOAA WaveWatch III significant wave heightMeters
antazi_aftAntenna azimuth angle aft lookDegrees
antazi_foreAntenna azimuth angle fore lookDegrees
azi_aftCell azimuth angle aft lookDegrees
azi_foreCell azimuth angle fore lookDegrees
ice_concentrationIce concentration
inc_aftCell incidence angle aft lookDegrees
inc_foreCell incidence angle fore lookDegrees
land_fraction_aftAverage land fraction for aft look
land_fraction_foreAverage land fraction for fore look
n_h_aftNumber of L1B TBs aggregated into H-pol aft look
n_h_foreNumber of L1B TBs aggregated into H-pol fore look
n_v_aftNumber of L1B TBs aggregated into V-pol aft look
n_v_foreNumber of L1B TBs aggregated into V-pol fore look
nedt_h_aftAggregated noise equivilent Delta T for H-pol aft lookDegrees kelvin
nedt_h_foreAggregated noise equivilent Delta T for H-pol fore lookDegrees kelvin
nedt_v_aftAggregated noise equivilent Delta T for V-pol aft lookDegrees kelvin
nedt_v_foreAggregated noise equivilent Delta T for V-pol fore lookDegrees kelvin
num_ambiguitiesNumber of wind vector ambiguties
quality_flagQuality flag
row_timeApproximate observation time for each rowUTC seconds of day
smap_ambiguity_dirSMAP ambiguity wind direction using ancillary SSSDegrees
smap_ambiguity_spdSMAP ambiguity wind speed using ancillary SSSMeters/second
smap_high_dirSMAP wind direction using ancillary SSSDegrees
smap_high_dir_smoothSMAP wind direction using ancillary SSS and DIRTH smoothingDegrees
smap_high_spdSMAP wind speed using ancillary SSSMeters/second
smap_spdSMAP wind speedMeters/second
smap_sssSMAP sea surface salinityPSU
smap_sss_uncertaintySMAP sea surface salinity uncertaintyPSU
tb_h_aftAverage brightness temperature for all H-pol aft looksDegrees kelvin
tb_h_bias_adjBrightness temperature bias adjustment for H-polDegrees kelvin
tb_h_foreAverage brightness temperature for all H-pol fore looksDegrees kelvin
tb_v_aftAverage brightness temperature for all V-pol aft looksDegrees kelvin
tb_v_bias_adjBrightness temperature bias adjustment for V-polDegrees kelvin
tb_v_foreAverage brightness temperature for all V-pol fore looksDegrees kelvin
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 JPL. 2023. JPL CAP 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 Fore,A.G, S.H. Yueh, W. Tang, B.W. Stiles, and A.K. Hayashi (2016). Combined Active/Passive Retrievals of Ocean Vector Wind and Sea Surface Salinity With SMAP. IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 54, NO. 12. p.7396-7404. DOI: 10.1109/TGRS.2016.2601486