RSS SMAP Level 2C Sea Surface Salinity NRT V6.0 Validated Dataset
(SMAP_RSS_L2_SSS_NRT_V6)| Version | 6.0 |
| Processing Level | 2 |
| Start/Stop Date | 2022-Jul-28 to Present |
| Short Name | SMAP_RSS_L2_SSS_NRT_V6 |
| Description | The SMAP-SSS level 2C near real-time (NRT) V6.0 dataset produced by the Remote Sensing Systems (RSS) and sponsored by the NASA Ocean Salinity Science Team, is a validated product that provides near real-time orbital/swath data on sea surface salinity (SSS) derived from the NASA's Soil Moisture Active Passive (SMAP) mission. SMAP, launched on January 31, 2015, was initially designed to measure and map Earth's soil moisture and freeze/thaw state to better understand terrestrial water, carbon and energy cycles, and 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 using the NRT SMAP Salinity Retrieval Algorithm, top of atmosphere brightness temperature (TB), wind speed and direction data for extreme winds, and other all necessary ancillary data and the results of all intermediate steps. The observations are global, provided on a 0.25° fixed Earth grid with an approximate spatial resolution of 70 km. 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. Each data file covers one 98-minute orbit (15 files per day), is available in netCDF-4 file format with about 5 hours l atency. This RSS SMAP-SSS V6.0 NRT dataset holds tremendous potential for scientific research and various applications. Given the SMAP satellite's near-polar orbit and sun-synchronous nature with its 1000km swath, 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. |
| DOI | 10.5067/SMP60-2SNRT |
| Measurement | OCEANS > SALINITY/DENSITY > SALINITY |
| Swath Width | 1000 km |
| Platform/Sensor | SMAP / Platform Name: Soil Moisture Active and Passive Observatory (SMAP) Orbit Period: 98.5 minutes Inclination Angle: 98.0 degrees SMAP L-BAND RADIOMETER SENSOR Name: SMAP L-Band Radiometer (SMAP L-BAND RADIOMETER) Swath Width: 1000.0 kilometers Description: Spacecraft angular distance from orbital plane relative to the Equator. |
| Project | Soil Moisture Active Passive (SMAP) |
| Data Provider | Publisher: 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: 2024-Mar-26 Resource: http://podaac.jpl.nasa.gov/smap |
| Format | netCDF-4 |
| Keyword(s) | RssSmapSSSv6, V6, SMAP, SMAP-SSS, Soil Moisture Active Passive, salinity, polar, sun-synchronous, sss, psu, NASA, project, mission, RSS, Remote Sensing System, REMSS, NRT, near real-time |
Questions related to this dataset? Contact podaac@podaac.jpl.nasa.gov
Resolution Spatial Resolution: 0.25 Decimal Degrees x 0.25 Decimal Degrees Temporal Resolution: Hourly - < Daily Coverage Region: GLOBAL North Bounding Coordinate: 90 degrees South Bounding Coordinate: -90 degrees West Bounding Coordinate: -180 degrees East Bounding Coordinate: 180 degrees Time Span: 2022-Jul-28 to PresentSwath Width: 1000 km Projection Projection Type: Grid |
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| us-west-2 | |
| podaac-ops-cumulus-protected/SMAP_RSS_L2_SSS_NRT_V6/ | |
| podaac-ops-cumulus-public/SMAP_RSS_L2_SSS_NRT_V6/ | |
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| Name | Long Name | Unit |
|---|---|---|
| alpha | Scan angle: +90 is left of forward. +270 is right of forward. | degree |
| anc_sea_ice_flag | ancillary sea-ice detection indicator | 1 |
| cellat | Latitude of OI Earth grid cell | degrees_north |
| cellon | Longitude of OI Earth grid cell | degrees_east |
| dtb_land_correction | TA land correction applied at TOA. Pol basis V,H | Kelvin |
| dtemp_ant | Empirical correction to physical temperature of reflector. Pol basis V,H | Kelvin |
| eaa | Azimuthal look angle relative to North | degree |
| eia | Earth incidence angle | degree |
| fland | land fraction within footprint | 1 |
| gallat | Latitudinal (polar) angle of specular reflection ray in ECI2000 | degree |
| gallon | Longitudinal (azimuthal) angle of specular reflection ray in ECI2000 | degree |
| gland | land fraction weighted by antenna gain | 1 |
| iqc_flag | 32-bit quality control flag | 1 |
| monglt | Moon glint angle | degree |
| pra | Polarization basis rotation angle (geometric part) | degree |
| pratot_exp | Expected total polarization basis rotation angle: Faraday rotation (from external TEC) + geometric | degree |
| rain | rain rate. estimated from NCEP could water profiles | mm h-1 |
| sea_ice_zones | sea-ice contamination zones | 1 |
| solar_flux | Ancillary solar flux (from NOAA SWPC) | 1e-22 W m-2 Hz-1 |
| sss_ref | Reference sea surface salinity from HYCOM | 1e-3 |
| sss_smap | SMAP sea surface salinity smoothed to approx 70km resolution | 1e-3 |
| sss_smap_40km | SMAP sea surface salinity at original 40km resolution | 1e-3 |
| sss_smap_40km_unc | total formal uncertainty estimate of SMAP sea surface salinity at original 40km resolution | 1e-3 |
| sss_smap_40km_unc_comp | formal uncertainty components of SMAP sea surface salinity at original 40km resolution | 1e-3 |
| sss_smap_unc | total formal uncertainty estimate of SMAP sea surface salinity smoothed to approx 70km resolution | 1e-3 |
| sss_smap_unc_comp | formal uncertainty components of SMAP sea surface salinity smoothed to approx 70km resolution | 1e-3 |
| sun_alpha | Sun azimuth angle in S/C coordinate system | degree |
| sun_beta | Sun zenith angle in S/C coordinate system | degree |
| sunglt | Sun glint angle. Negative value means that sun ray pierces the Earth. | degree |
| surtep | Ancillary sea surface temperature (from CMC) | Kelvin |
| ta_ant | unfiltered antenna temperature. Pol basis V,H,S3,S4 | Kelvin |
| ta_ant_calibrated | Antenna temperature after correcting for emissive reflector and TND adjustment. Pol basis V,H,S3,S4 | Kelvin |
| ta_ant_exp | Expected (RTM) antenna temperature before any losses. This is to be compared with ta_ant_calibrated. Pol basis V,H,S3,S4 | Kelvin |
| ta_ant_filtered | RFI filtered antenna temperature. Pol basis V,H,S3,S4 | Kelvin |
| ta_earth | Antenna temperature after correcting for cold space, galaxy, sun, moon. Pol basis V,H,S3,S4 | Kelvin |
| ta_gal_dir | TA of direct galaxy intrusion. Pol basis I,Q,S3 | Kelvin |
| ta_gal_ref | TA of reflected galaxy intrusion. Pol basis I,Q,S3 | Kelvin |
| ta_sun_dir | TA of direct sun intrusion. Pol basis I,Q,S3 | Kelvin |
| ta_sun_ref | TA of reflected sun intrusion. Pol basis I,Q,S3 | Kelvin |
| tb_consistency | sqrt(chi2) of MLE in SSS retrieval | Kelvin |
| tb_sur | Brightness temperature at rough ocean surface BEFORE applying roughness correction. Pol basis V,H,S3,S4 | Kelvin |
| tb_sur0 | Brightness temperature at flat ocean surface AFTER applying roughness correction. Pol basis V,H,S3,S4 | Kelvin |
| tb_sur0_exp | Expected (RTM) at flat ocean surface. SIC added. This is to be compared with tb_sur0, before SIC. Pol basis V,H,S3,S4 | Kelvin |
| tb_sur0_sic | Brightness temperature at flat ocean surface after applying roughness correction and sea-ice correction. Pol basis V,H,S3,S4 | Kelvin |
| tb_toa | Brightness temperature at top of atmosphere BEFORE applying land correction. Pol basis V,H,S3,S4 | Kelvin |
| tb_toa_lc | Brightness temperature at top of atmosphere AFTER applying land correction. Pol basis V,H,S3,S4 | Kelvin |
| tb_toi | Brightness temperature at top of ionosphere. Pol basis V,H,S3,S4 | Kelvin |
| tbdw | Atmospheric downwelling brightness temperature | Kelvin |
| tbup | Atmospheric upwelling brightness temperature | Kelvin |
| TEC | Vertically integrated electron content between surface and S/C | 1e16 m-2 |
| temp_ant | Physical temperature of reflector from L1B files. Pol basis V,H | Kelvin |
| time | Time of observation | seconds since 2000-1-1 0:0:0 0 |
| tran | Total atmospheric transmittance | 1 |
| windir | Ancillary wind direction relative to North (from NCEP, meteorological convention) that is used in surface roughness correction | degree |
| winspd | Ancillary sea surface wind speed from CCMP NRT that is used in surface roughness correction | m s-1 |
| zang | Orbital position angle of S/C. 0 is South. 90 is equator ascending. 180 is North. 270 is equator descending. | degree |
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). 2024. SMAP Sea Surface Salinity Products. Ver. 6.0. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at https://doi.org/10.5067/SMP60-2SNRT
For more information see Data Citations and Acknowledgments.
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| 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. . |
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| Version | Dataset | Version Date | Status | |
|---|---|---|---|---|
| 6.0 | RSS SMAP Level 2C Sea Surface Salinity V6.0 Validated Dataset | 2024-01-08 | ACTIVE | 2024-01-08T18:42:00.000Z |
| 6.0 | RSS SMAP Level 2C Sea Surface Salinity NRT V6.0 Validated Dataset | 2024-01-08 | ACTIVE | 2024-01-08T18:49:00.000Z |
| 5.3 | RSS SMAP Level 2C Sea Surface Salinity V5.3 Evaluation Dataset | 2024-04-16 | COMPLETE | 2024-04-16T15:59:00.000Z |
| 5.0 | RSS SMAP Level 2C Sea Surface Salinity V5.0 Validated Dataset | 2022-07-19 | ACTIVE | 2022-07-19T17:30:00.000Z |
| 4.0 | RSS SMAP Level 2C Sea Surface Salinity V4.0 Validated Dataset | 2021-09-01 | ACTIVE | 2021-09-01T15:58:00.000Z |
| 3.0 | RSS SMAP Level 2 Sea Surface Salinity V3.0 40km Validated Dataset | Present | RETIRED. | |
| 2.0 | RSS SMAP Level 2C Sea Surface Salinity V2.0 Validated Dataset | 2024-03-20 | RETIRED. | 2024-03-20T15:30:00.000Z |