RSS SMAP Level 2C Sea Surface Salinity V5.0 Validated Dataset
(SMAP_RSS_L2_SSS_V5)| Version | 5.0 |
| Processing Level | 2 |
| Start/Stop Date | 2015-Apr-01 to Present |
| Short Name | SMAP_RSS_L2_SSS_V5 |
| Description | The version 5.0 SMAP-SSS, level 2C product contains the fourth release of the validated sea surface salinity orbital/swath data from the NASA Soil Moisture Active Passive (SMAP) observatory, and is 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. The SMAP-SSS L2C product includes data for a range of parameters: derived sea surface salinity (SSS) with SSS-uncertainty, brightness temperatures for each radiometer polarization, antenna temperatures, collocated wind speed, data and ancillary reference surface salinity data from HYCOM, rain rate, quality flags, and navigation data. Each data file covers one 98-minute orbit (15 files per day). 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 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. |
| DOI | 10.5067/SMP50-2SOCS |
| Measurement | OCEANS > SALINITY/DENSITY > SALINITY |
| Swath Width | 1000 km |
| Platform/Sensor | SMAP / Platform Name: NASA Soil Moisture Active Passive (SMAP) (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: 2022-Feb-25 Resource: http://podaac.jpl.nasa.gov/smap |
| Format | netCDF-4 |
| Keyword(s) | RssSmapSSSv5, V5, SMAP, SMAP-SSS, Soil Moisture Active Passive, salinity, polar, sun-synchronous, sss, psu, NASA, project, mission, RSS, Remote Sensing System, REMSS |
Questions related to this dataset? Contact podaac@podaac.jpl.nasa.gov
Resolution Spatial Resolution: 39000 Meters x 47000 Meters 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: 2015-Apr-01 to PresentSwath Width: 1000 km Projection Projection Type: Swath Ellipsoid: WGS 84 |
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| us-west-2 | |
| podaac-ops-cumulus-protected/SMAP_RSS_L2_SSS_V5/ | |
| podaac-ops-cumulus-public/SMAP_RSS_L2_SSS_V5/ | |
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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 |
| dtb_sea_ice_correction | TB sea-ice correction applied at TB SUR 0. 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 |
| gice_est | estimated sea ice fraction weighted by antenna gain | 1 |
| 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 | IMERG rain rate. Resampled to SMAP resolution. | 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). 2022. SMAP Sea Surface Salinity Products. Ver. 5.0. PO.DAAC, CA, USA. Dataset accessed [YYYY-MM-DD] at https://doi.org/10.5067/SMP50-2SOCS
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 |