CATDS (CNES, IFREMER, LOCEAN, ACRI)

The base products, for all the CATDS-PDC (Centre Aval de Traitement des Données SMOS - Production & Dissemination Center) processing chains, are the SMOS L1B products - https://doi.org/10.57780/SM1-e20cf57 - from ESA (European Space Agency).

From these, brightness temperatures at various incidence angles are reconstructed. The Sea Surface Salinity (SSS) are retrieved from multi-angular brightness temperatures through a maximum likehood Bayesian approach in which measured Tb and Tb simulated using a forward direct model are compared (see Zine et al. 2008 for a general description of the retrieval method, and pro_con table for a summary of the similarities/differences with respect to ESA level 2 ocean salinity processing).

The qualified L3OS 2Q product is an intermediate product, that provides, in daily files, SSS corrected from land-sea contamination and latitudinal bias. Ascending and descending orbits are processed separately.

Products from reprocessing RE07 are available for the period 01/2010 - 05/2021. Products from operational (OPER) processing are available since 06/2021. Reprocessed products and operational products are derived using the same algorithm and configuration, hence ensuring the temporal continuity.

These products are generated with a delay of 5 days (Please see below for alternative 1-day delay products).

File naming:

SM_clas_MIR_CSF2Qx_startdate_enddate_vvv_ccc_7

- clas : File class (OPER : operational mode, REXX : reprocessing xx)

- x : A for ascending orbit, D for descending orbit

- startdate : sensing start date/time of the data (format yyyymmddThhmiss)

- enddate : sensing end date/time of the data (format yyyymmddThhmiss)

- vvv : version number of the processor generating the product

- ccc : file counter

File format:

In each archive file (.tgz extension), there are two files

- A Header file (.HDR), which is a text file, in XML Earth Explorer Header format

- A Data file (.DBL.nc), which is a netcdf file, format variant 2 (netcdf 3 with 64 bits offset option)

Alternative 1-day delay products:

Since 07/2019, 1-day delay products are also available, in operational (OPER) processing only.

These products are only available by FTP (i.e. not by Sipad). The paths and file names are identical, except that the "MIR" tags are replaced by "NRT".

Simplified version:

This product is also available on Copernicus Marine Service as product MULTIOBS_GLO_PHY_SSS_L3_MYNRT_015_014.

The files are in NetCDF 4, with the alternative file naming:

CATDS_CSF2Qx_startdate_enddate_vvv_p.nc

- x : A for ascending orbit, D for descending orbit

- startdate : sensing start date/time of the data (format yyyymmddThhmiss)

- enddate : sensing end date/time of the data (format yyyymmddThhmiss)

- vvv : version number of the processor generating the product

- p: processing step: 1 for NRT (1-day delay), 2 for regular (5-day delay), 3 for reprocessed.

Reference :

Boutin J., Vergely J.L., Marchand S., D'Amico F., Hasson A., Kolodziejczyk Nicolas, Reul Nicolas, Reverdin G., Vialard J. (2018). New SMOS Sea Surface Salinity with reduced systematic errors and improved variability. Remote Sensing of Environment, 214, 115-134. Publisher's official version : http://doi.org/10.1016/j.rse.2018.05.022 , Open Access version : http://archimer.ifremer.fr/doc/00441/55254/