Simulated SWOT Sea Surface Height products

Contents: Simulated SWOT Sea Surface Height products KaRIn and Nadir.

DOI: 10.24400/527896/a01-2021.006   -  more metadata

Description: The SWOT Sea Surface Height simulated products contain:

  • Level-2 Low Rate (LR) data (L2_LR_SSH) designed for ocean surfaces. Two phases have been simulated: the CalVal phase which is at 1 day repetitive orbit and the Science phase which is at 21 days repetitive orbit. For each phase, both KaRin and Nadir measurements are provided. The provided Sea Surface Heights are calculated with 2 models: the Mercator Océan GLORYS 12v1 model (GLORYS - Mercator Ocean (mercator-ocean.fr)) and the MITgcm LLC4320 model (ECCO Project´s 1/48° MITgcm Simulation (nasa.gov)).
    Other geophysical variables are given in the files as well as simulated fields estimated with the CNES/JPL simulator https://github.com/CNES/swot_simulator with the reference Gaultier, L., Ubelmann, C., & Fu, L. (2016). The Challenge of Using Future SWOT Data for Oceanic Field Reconstruction, Journal of Atmospheric and Oceanic Technology, 33(1), 119-126, https://doi.org/10.1175/JTECH-D-15-0160.1 
  • Level-2 and Level-3 SSH corrected by estimations of simulated errors. The Level 2 correction is based on method used in NASA/CNES ground segment and the Level 3 multimission correction has been developped for DUACS. One phase has been computed: the Science phase which is at 21 days repetitive orbit. Only KaRin measurements are provided. Each file contains the simulated errors to retrieve, the correction computed with the XCAL algorithm and the SSH kaRin containing both the simulated errors and the correction. The reference for the XCAL algorithm is Dibarboure et al., June 2022, SWOT Science Team meeting, SWOT simulated Level-2 and Level-3 data-driven calibration. 
  L2_LR_SSH Corrected SSH L2 Corrected SSH L3
Model Glorys or
MITgcm LLC4320		 Glorys Glorys
Phases Calval and Science Science Science
KaRin or Nadir measurements KaRin and Nadir KaRin KaRin
Karin noise Wave dependent Wave dependent Wave dependent
Systematic error CBE2021 (Dibarboure et al., 2022) CBE2021 (Dibarboure et al., 2022) CBE2021 (Dibarboure et al., 2022)
Empirical correction no correction L2 XCAL correction L3 XCAL correction

Variables of Level-2 Low Rate (LR) data (L2_LR_SSH)

For the KaRIn products, the following variables are filled (the others are at default values): 

  • ssh_karin (= GLORYS simulated+ Errors simulated),
  • ssha_karin (= ssh_karin - mean of GLORYS maps over the period),
  • ssh_karin_2 (= ssh_karin),
  • ssha_karin_2 (= ssha_karin),
  • ssha_karin_qual,
  • distance_to_coast,
  • ancillary_surface_classification_flag,
  • dynamic_ice_flag,
  • cross_track_distance,
  • mean_sea_surface_cnescls,
  • mean_sea_surface_cnescls_uncert,
  • geoid,
  • depth_or_elevation,
  • internal_tide_hret (only for GLORYS),
  • internal_tide_sol2 (only for GLORYS),
  • ocean_tide_fes (only for MITgcm),
  • dac (only for MITgcm),
  • ice_conc.

The following variables are simulated by the CNES/JPL Simulator : https://github.com/CNES/swot_simulator 

  • simulated_true_ssh_karin (ssh_karin - Errors simulated),
  • simulated_error_baseline_dilation,
  • simulated_error_timing,
  • simulated_error_roll,
  • simulated_error_phase,
  • simulated_error_orbital,
  • simulated_error_karin.

Variables for the Level-2 and Level-3 corrected SSH datasets

The following variables are provided: 

  • height_cor_xover: Height correction from KaRIn crossover calibration. See Dibarboure et al., June 2022, SWOT Science Team meeting, "SWOT simulated Level-2 and Level-3 data-driven calibration" for more details on the calibration process. This correction is already applied to the SSH kaRin by adding its value.
  • simulated_errors: This is derived from a simulation using the most faithful pre-launch error scenario (Current Best Estimates 2021). It contains the sum of the various systematic errors identified (attitude knowledge, interferometric phase, KaRIn mast length imprecision), details are described in Dibarboure et al., 2022.
  • ssh_karin: Corrected SSH kaRin. SSH kaRin containing the simulated errors and the crossover calibration. This SSH also contains a Wet Tropospheric error simulation and a white noise simulation for the KaRIn instrument.
    ssh_karin = (true_ssh + wet_tropo_err + karin_instrumental_noise) + simulated_errors + height_cor_xover.

Use: geophysical studies, oceanography, may be of limited use over other surfaces. Studies performing simulation measurements.

Geographic coverage: Global. The data from the KaRIn swath are spanning 60km on both sides of nadir with a nadir gap. All the variables are given on a swath-aligned 2x2 km2 grid and sea surface Height on a 250x250 m2 native grid. 

Data access service: download here. Note that L2_LR_SSH products are also distributed by PODAAC/JPL here.

Condition of use: No condition is required to get access to the data

Format: NetCDF

References:

User manual:  SWOT product description for L2_LR_SSH products

Copyright: 2011-2012 and 2014-2015 Cnes

Product Phase Satellite pass Access service  Data period Data used File weight

Simulated SWOT product
Mercator Océan GLORYS
(L2_LR_SSH)

 Science KaRIn https://data.aviso.altimetry.fr/aviso-gateway/data/simulated_SWOT_products/L2_LR_SSH/  From 2014/04/12 to 2015/12/31 one pass per file <14Mb
Nadir <270Kb
CalVal KaRIn <14Mb
Nadir <270Kb

Simulated SWOT product
MITgcm LLC4320
(L2_LR_SSH)

 Science KaRin From 2011/11/13 to 2012/11/12 <14Mb
Nadir <270Kb
CalVal KaRin <14Mb
Nadir <270Kb

Simulated SWOT product
Mercator Océan GLORYS -
corrected SSH - L2

 Science KaRIn https://data.aviso.altimetry.fr/aviso-gateway/data/simulated_SWOT_products/L2_SSH_Corrected/  From 2014/04/12 to 2015/12/31 one pass per file 19 Mb
Simulated SWOT product
Mercator Océan GLORYS -
corrected SSH - L3		 https://data.aviso.altimetry.fr/aviso-gateway/data/simulated_SWOT_products/L3_SSH_Corrected/ 14 Mb