SMAP Level 3 Sea Surface Salinity Standard Mapped Image 8-day, Version 4.3

The PI-produced JPL V4.3 SMAP Sea Surface Salinity (SSS) and extreme winds Level 3 (L3) standard datasets is based on the JPL Combined Active-Passive (CAP) algorithm applied to data from the NASA Soil Moisture Active Passive (SMAP) observatory. For science applications, use of the standard products is strongly advised.

SMAP SSS V4.2 accommodates changes in the underlying Level 1B-TB data resulting from the SMAP mission data reprocessing in June 2018. Updates with version 4.2 include: improvement in the brightness temperature (TB) calibration using an adjusted reflector emissivity, inclusion of a Sea Surface Temperature (SST) dependent flat surface emissivity model, use of updated land correction tables, and inclusion of averaged ice concentration ancillary data in the V4.2 datasets. Data begins on 1 April 2015 and is ongoing. Data sets provided here include L3 mapped, global coverage salinity datasets: an 8-day running mean dataset based on the repeat orbit of the SMAP mission, along with a monthly average dataset. The L3 data are gridded at 0.25 x 0.25. The spatial resolution of all four datasets is approximately 60 km.

Version 4.3 included only minor changes to the TB calibration and the averaging for L2B to L3. The residual TB calibration tables they modified to no longer be a function of antenna azimuth angle as they were in version 4.2. The change to the TB correction tables has fixed the ascending / descending bias issue that is present in version 4.2.

They added an additional quality criteria to L2B SWCs to check before inclusion in L3 averaging: in V 4.3 they require that the V-pol - H-pol TB be larger than 25 K.

The JPL SMAP-SSS CAP V4.3 datasets are described and discoverable via the PO.DAAC data portal.

The SMAP Algorithm Theoretical Basis Document (ATBD), validation analysis and file specification document together with other primary technical documentation are available from the podaac. General information regarding the SMAP mission is available from the mission website and also via PO.DAAC's SMAP and salinity webpages.

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

JPL SMAP-SSS CAP V4.3 ATBD Validation and Users Guide
SMAP-SSS Project and Instrument Overview

Comments/Questions? Please contact or visit the PO.DAAC Forum.

sea surface salinity (psu), reference sea surface salinity from hycom (psu), sea surface temperature (k), smap 10 m wind speed (m s-1), smap 10 m wind speed (using ancillary sss) (m s-1), sum of gaussian weighting factors, ice concentration, average land fraction, smap sss uncertainty (1e-3)
Zonal Global by 0.25 deg
Meridional Global by 0.25 deg
Vertical Surface
Temporal Apr 4, 2015 to Aug 22, 2020 by 1 day
Volume ~7MB per day
Source JPL SMAP-SSS CAP V4.3 ATBD Validation and Users Guide
Acquired March 17, 2020
APDRC contact
Supplements JPL SMAP-SSS V4.2 Data User Guide