Which Salinity Data are Best for You?

SMAP SSS Products Overview

SMAP
RSS (V4) JPL* (4.3)
Antenna type Spinning; 99% reflective (1% emissive)
Global coverage / Repeat orbit 3 days / 8 days (exact)
Data products available:
  • L2 is Level-2 swath
  • L3 is Level-3 gridded
L2C: Standard
L3: 8-day Running Mean; Monthly
L2B: Standard; Near-real-time (6 hours)
L3: 8-day Running Mean, Monthly
Gridding 0.25° x 0.25° 0.25° x 0.25°
Feature resolution 70 km** ~60 km**
  • * JPL's SMAP SSS data set is also referred to as the "Combined Active Passive (CAP)" product.
  • ** SMAP's native 40-km variable is relatively noisy. As a result, SMAP products are spatially averaged to larger footprints (i.e., 70 km, 60 km) to reduce data noise, especially for open ocean applications.

SMAP Ancillary Data Sources

RSS (V4) JPL (4.3)
SST GHRSST Level 4 from Canadian Meteorological Center [CMC] NOAA Optimum Interpolation [OI]
Atmospheric profile fields NCEP GDAS 1-deg, 6-hour fields [GDAS] N/A
Solar flux Ancillary mean solar flux from NOAA Space Weather Prediction Center [SWPC] N/A
Wind speed & direction CCMP V2 [CCMP] National Centers for Environmental Prediction Global Forecast System [GFS]
Land mask ODPS static 1-km land/water mask from GSFC [ODPS] US Geological Survey 30-second Land Use Data [USGS] integrated using SMAP antenna patterns
Rain IMERG Rain effect and rain roughness corrections are in development
Dielectric constant Meissner and Wentz 2004, 2012 Meissner and Wentz 2004, 2012
Galactic map Dinnat, E.; Le Vine, D.; Abraham, S.; Floury, N. Map of Sky Background Brightness Temperature at L-Band (2018) Own derived galaxy correction (3.2.2 of User Guide)
Total electron content (TEC) IGS IONEX TEC files [TEC] N/A
Sea ice fraction RSS Version 8 AMSR-2 ocean suite (Wentz et al., 2014) [RSS] National Centers for Environmental Prediction [NCEP]
Argo salinity from Scripps Institution of Oceanography (SIO) Included to facilitate comparison of rain-filtered SMAP SSS; not used in the actual salinity algorithm [SIO] Used for comparison but not included in data files.
Reference salinity field Hybrid Coordinate Ocean Model [HYCOM] Hybrid Coordinate Ocean Model [HYCOM]
Significant wave height N/A NOAA WaveWatch III [WaveWatch III]

Level-3 Gridded Products

State of the Ocean (SOTO), a web-based tool

An interactive, web-based tool to generate informative maps, animations, and plots that communicate and promote the discovery and analysis of the State Of The Oceans (SOTO). SOTO is a suite of tools presented through an interactive, web-based visualization front end. It provides access to a broad range of satellite-derived products and key parameters of interest to the oceanographic community. SOTO facilitates visual exploration and comparative analysis of physical oceanographic data, enabling your research.

The "+ ADD MORE" button can be used to activate sea surface salinity (SSS) data layers:

  • SAC-D/Aquarius
  • SMAP JPL
  • SMAP JPL

Characteristics of layers can be updated:

  • Repositioned (e.g., 1 is at top, 2 is just below, etc.)
  • Toggled On/Off
  • Changed in terms of opacity (i.e., to see multiple layers simultaneously)
Live Access Server (LAS) web-based tool

Live Access Server (LAS) is a web-based Level-3 (L3) data visualization and subsetting tool, designed to provide flexible access to geo-referenced scientific data. It enables users to: visualize data with on-the-fly graphics; request custom subsets of variables in a choice of file formats; access background reference material about the data (metadata); compare (difference) variables from distributed locations.

The "Data Set" button can be used to access the following datasets (SSS data are marked by asterisks, *):

  • SAC-D/Aquarius (16 data products)
  • SMAP RSS (2 data products) with the following options
    • Ancillary sea surface temperature
    • Average land fraction (weighted by antenna gain)
    • Average land fraction within 3dB contour
    • Average sea ice fraction (weighted by antenna gain)
    • Number of observations for L3 average of SSS at 40km resolution
    • Number of observations for L3 average of SSS smoothed to approx. 70km resolution
    • Reference sea surface salinity from HYCOM
    • *SMAP sea surface salinity at original 40km resolution
    • *SMAP sea surface salinity smoothed to approx. 70km resolution
  • Characteristics of layers can be updated:
    • Repositioned (e.g., 1 is at top, 2 is just below, etc.)
    • Toggled On/Off
    • Changed in terms of opacity (i.e., to see multiple layers simultaneously)

NOTE: To see changes to updates to data sets, map type, date, etc., click the "Update Plot" button at upper left.

A tutorial for using LAS with Aquarius salinity datasets is provided on YouTube.


Level-2 Swath Products

The High-level Tool for Interactive Data Extraction
The High-level Tool for Interactive Data Extraction (HiTIDE), allows users to subset and download swath datasets. Users can search across a wide variety of parameters, such as variables, sensors and platforms, and filter the resulting data based on spatial and temporal boundaries of interest to the user. HiTIDE goes even further, offering instant previews of variable imagery, allowing users to rapidly find data of interest for download and further, rigorous scientific analysis. The "Variable" pull-down menu can be used to select "Salinity" data:
  • SAC-D/Aquarius
  • SMAP RSS
A short tutorial for using HiTide is available.