Earth Data School
About
Full catalog/SMAP_RSS_L2_SSS_V6
SMAP_RSS_L2_SSS_V6·v6.0·dataset

How salty the sea surface is (SMAP)

RSS SMAP Level 2C Sea Surface Salinity V6.0 Validated Dataset
ocean NASA POCLOUD Level 2 netCDF-4
In plain English

What it measures. How salty the very top layer of the sea is, along the satellite's swath, with uncertainty estimates and the underlying microwave readings.

How it's made. Retrieved from natural microwave energy measured by NASA's SMAP satellite, with corrections for surface roughness using outside wind data; produced by Remote Sensing Systems.

How & where you'd use it. Mapping ocean salinity to study currents, the water cycle, and climate; this validated version removes several known biases for better accuracy.

What's measured

OCEANS › SALINITY/DENSITY › SALINITY › SALINITY

Coverage & cadence

  • Time span2015-04-01 → ongoing
  • Measured bySMAP (SMAP L-BAND RADIOMETER)
  • Processing levelLevel 2
  • Spatial extent-180, -90, 180, 90
  • FormatsnetCDF-4
  • StatusACTIVE

What you can do with it

  • Watch sea-surface temperature and marine heatwaves
  • Spot algal blooms and ocean-colour shifts
  • Support fisheries and coastal monitoring
Official description

The RSS SMAP level 2C sea surface salinity 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 orbital/swath data on sea surface salinity (SSS) derived from the NASA's Soil Moisture Active Passive (SMAP) mission. The SMAP satellite was launched on 31 January 2015 with 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. 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. 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. 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), is available in netCDF-4 file format with about 4 days latency. 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 standard product of the SMAP Version 6.0 release is the smoothed salinity product with a spatial resolution of approximately 70 km. This activity was informed by the Satellite Needs Working Group (SNWG), an interagency effort of the U.S. Government dedicated to identifying and addressing Earth observation needs across U.S. civilian federal agencies.

Get the data

smap_rss_l2_sss_v6_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="SMAP_RSS_L2_SSS_V6",
    version="6.0",
    bounding_box=(-122.5, 37.2, -121.8, 37.9),  # your area (W,S,E,N)
    temporal=("2024-01-01", "2024-12-31"),       # your dates
)
files = earthaccess.open(results)   # stream straight from POCLOUD
Browsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package.