SWOT • KaRIn • L2_LR_SSH

Version C and Version D LR SSH Products

A compact summary of the SWOT Level-2 KaRIn Low Rate Sea Surface Height product release history, coverage, and key differences.

Granule: single pass Files per granule: 4 Nominal latency: < 45 days Main product: L2_LR_SSH
SWOT L2_LR_SSH product description and the Version C / D KaRIn release notes.

Overview

The L2_LR_SSH product is SWOT’s KaRIn low-rate sea-surface-height product for oceanography. It provides sea surface height (SSH), sea surface height anomaly (SSHA), significant wave height, sigma0, wind speed, uncertainties, quality flags, and supporting geophysical and correction information. Each granule spans one spacecraft pass and is distributed as four NetCDF files.

This is a summary of the product documents Version C and Version D on PODAAC.

Item Version C Version D
Major release meaning First public Version C KaRIn generation, later updated with PIC2 forward processing. Next major KaRIn generation with updated calibrations, algorithms, and reprocessing.
Recommended choice Use the highest available C product for dates before D exists. Preferred whenever available.
Reprocessing scope PGC0 only for early mission subset. PGD0 reprocessing from calibration-phase start through 2025-04-27.
Forward processing PIC0 then PIC2. PID0 from 2025-04-28 onward.

Version information and time coverage

Version family CRID Processing type Time coverage stated in release notes Orbit / cycle notes
Version C PGC0 Reprocessed 2023-03-30 to 2024-01-25 Calibration cycles 475–578 and science cycles 1–9
Version C PIC0 Forward 2024-01-25 to 2024-10-15 Science cycle 10 to part of cycle 22
Version C PIC2 Forward 2024-10-16 to 2025-04-27 Part of science cycle 22 through end of cycle 31; no PGC2 products
Version D PGD0 Reprocessed 2023-03-30 to 2025-04-27 Calibration cycles 475–578 and science cycles 1–31
Version D PID0 Forward 2025-04-28 onward Approximately science cycle 32 onward
Where both forward and reprocessed products exist for the same time, the release notes advise using the reprocessed product: PGC0 over PIC0, and PGD0 over PID0.

How to read the CRID

CRID pattern

P [I or G] [C or D] [minor]
  • P: fixed prefix
  • I: forward-processed
  • G: reprocessed
  • C or D: major version
  • Final character: minor release code

Examples

  • PIC0: Version C forward product
  • PGC0: Version C reprocessed product
  • PIC2: updated Version C forward product with resolved issues
  • PID0: Version D forward product
  • PGD0: Version D reprocessed product

L2_LR_SSH file set

Each pass-sized granule is distributed as four NetCDF files. The first three are on a geographically fixed 2 km swath-aligned grid; the fourth is on the native unsmoothed grid.

File Main purpose Sampling
Basic Core SSH / SSHA and quality information 2 km fixed swath-aligned grid
WindWave SWH, sigma0, wind speed, and model wave/wind context 2 km fixed swath-aligned grid
Expert Superset of Basic + WindWave with detailed corrections and ancillary fields 2 km fixed swath-aligned grid
Unsmoothed Near-native SSH / sigma0 fields on the center-beam native grid ~250 m posting, ~500 m resolution

The product latency stated in the product description is less than 3 days from data collection.

Most important Version D changes relative to Version C

Change Main LR SSH implication
KaRIn height calibration refinement Short-wavelength SSH changes on the order of a few millimeters
Range-Doppler coupling correction Fixes pass-scale height variations of order centimeters
Radiometer calibration update Reduces left-right relative bias to below about 0.2 mm
Crossover processing update Improved crossover correction performance and flagging
Geoid bug fix Fixes reported geoid errors of order 10 cm
MSS / MDT / tide model updates Uses newer MSS, MDT, and FES2022b tide models
SSHA update Non-equilibrium long-period ocean tide is applied
New variables in L2_LR_SSH SSHA added at unsmoothed posting; mitigation Doppler added; spacecraft event flag added to Expert
LR over-land processing improvements Fewer height artifacts over land
LR volumetric correlation processing Improved KaRIn significant wave height retrievals

Practical use guidance

For a continuous LR SSH time series, use Version D whenever it exists. For dates before the Version D reprocessing/final coverage, fall back to the highest available Version C product. A practical sequence is: PGD0 → PID0 → PIC2 → PGC0/PIC0.

Primary sources used: SWOT Version C release note (2024-10-14), SWOT Version D release note (2025-12-19), SWOT L2_LR_SSH Product Description Document Revision C (2025-02-24), and SWOT User Handbook Revision A (2025-03-04).