NOAA produces two lines of gridded 0.02deg super-collated L3S LEO SST datasets from Low Earth Orbiting (LEO) satellites, one from the NOAA afternoon JPSS (L3S_LEO_PM) and the other from the EUMETSAT mid-morning Metop-FG (L3S_LEO_AM). The L3S_LEO_AM is derived from Metop-A, -B and -C. The Metop-FG satellite program was jointly established by ESA and EUMETSAT. The US NOAA, under the Initial Joint Polar System Agreement with EUMETSAT, has contributed three AVHRR sensors capable of collecting and transmitting data in the Full Resolution Area Coverage (FRAC; 1km/nadir) format. The L3S_LEO_AM dataset is produced by aggregating three L3U datasets from MetOp-FG satellites ( http://doi.org/10.5067/GHMTA-3US28 , http://doi.org/10.5067/GHMTB-3US28 , http://doi.org/10.5067/GHMTC-3US28 ) and covers from Dec 2006-present. The L3S-LEO-AM data are reported in two files per 24hr interval, one daytime and one nighttime (nominal Metop local equator crossing times around 09:30/21:30, respectively), in NetCDF4 format, compliant with the GHRSST Data Specification version 2 (GDS2). The Near-Real Time (NRT) L3S-LEO data are archived at PO.DAAC with approximately 6 hours latency and then replaced by the Delayed Mode files about 2 months later, with identical file names. The NRT/DM data are seamlessly stitched with the full-mission Reanalysis (RAN). In addition to SST, the L3S-LEO files report the location and intensity of thermal fronts. The ACSPO L3S products are monitored and validated against in situ data in the NOAA iQuam system ( https://www.star.nesdis.noaa.gov/socd/sst/iquam ) in the NOAA SQUAM system ( https://www.star.nesdis.noaa.gov/socd/sst/squam ). Quality of SST imagery and clear-sky mask is evaluated in the NOAA ARMS system ( https://www.star.nesdis.noaa.gov/socd/sst/arms ). NOAA plans to include data from other mid-morning platforms and sensors, such as Metop-SG METImage, into L3S_LEO_AM.

Level 3, four times a day, sub-skin Sea Surface Temperature derived from AVHRR on Metop satellites and VIIRS or AVHRR on NOAA and NPP satellites, over North Atlantic and European Seas and re-projected on a polar stereographic at 2 km resolution, in GHRSST compliant netCDF format. This catalogue entry presents Metop-A North Atlantic Regional Sea Surface Temperature. SST is retrieved from infrared channels using a multispectral algorithm and a cloud mask. Atmospheric profiles of water vapor and temperature from a numerical weather prediction model, Sea Surface Temperature from an analysis, together with a radiative transfer model, are used to correct the multispectral algorithm for regional and seasonal biases due to changing atmospheric conditions. The quality of the products is monitored regularly by daily comparison of the satellite estimates against buoy measurements. The product format is compliant with the GHRSST Data Specification (GDS) version 2.Users are advised to use data only with quality levels 3,4 and 5.

The DTM is a compilation of multibeam echosounder surveys acquired in 2013. The resolution is 1/64 arc-minutes (~30m). Surveys are located on the Capbreton Submarine Canyon (France) with depths from -4.7m to -344.9m. Depths are referenced to the Lowest Astronomical Tide and the coordinates are expressed into the WGS84 reference frame. The surveys which compose the DTM are S201306500-09 and S201306500-11. Data and metadata associated to these surveys are available on the website http://diffusion.shom.fr/pro/lots-bathy.html. The DTM is not to be used for navigation.

The Level-2P (L2P) products are pre-operational homogenized, mono-mission satellite altimetry datasets generated by the DUACS production system. They provide 1‑Hz along‑track SLA data together with the full set of standardised geophysical and environmental corrections (e.g., tide‑free sea level, inverse barometer, sea‑state bias, atmospheric corrections). The L2P SLA datasets are the primary input for the higher‑order DUACS processing chain that yields the operational sea‑level (Level-3 and Level-4) products distributed by the Copernicus Marine Service (CMS) and the Copernicus Climate Change Service (C3S). **Processing Timeliness:** - **Near-Real-Time (NRT)**: Rapid delivery windows (under 3h – up to 24h for the newest passes) for operational marine forecasting. - **Short Time Critical (STC)**: Intermediate latency (24h – 3 days) streams optimized for quick-turnaround cal/val and monitoring. - **Non-Time Critical (NTC)**: Science‑quality dataset (30 days – up to 90 days) with the most stable baseline corrections; foundation for long‑term climate analyses. The L2P SLA NRT/STC 20Hz data products version 3.0 (DUACS DT 2021 baseline) are available for the following missions: Jason-3, Sentinel‑3A, Sentinel‑3B and Sentinel‑6 Michael Freilich (MF). The L2P SLA NTC 1Hz data products version 3.0 (DUACS DT 2021 baseline) are available for the following missions: ERS‑1, TOPEX/Poseidon, ERS‑2, Geosat‑Follow‑On, Jason‑1, Envisat, Jason‑2, CryoSat‑2, Haiyang‑2A, SARAL/AltiKa, Jason‑3, Sentinel‑3A, Sentinel‑3B and Sentinel‑6 Michael Freilich (MF).

The SWOT L3_LR_SSH product provides ocean topography measurements obtained from the SWOT KaRIn and nadir altimeter instruments, merged into a single variable. The dataset includes measurements from KaRIn swaths on both sides of the image, while the measurements from the nadir altimeter are located in the central columns. In the areas between the nadir track and the two KaRIn swaths, as well as on the outer edges of each swath (restricted to cross-track distances ranging from 10 to 60 km), default values are expected. SWOT L3_LR_SSH is a cross-calibrated product from multiple missions that contains only the ocean topography content necessary for thematic research (e.g., oceanography, geodesy) and related applications. This product is designed to be simple and ready-to-use, and can be combined with other altimetry missions. The SWOT L3_LR_SSH product is a research-orientated extension of the L2_LR_SSH product, distributed by the SWOT project (NASA/JPL and CNES) and managed by the SWOT Science Team project DESMOS. The "Basic" version of SWOT L3_LR_SSH (the "Expert" version is the subject of a separate metadata sheet) includes only the SSH anomalies and mean dynamic topography.

Level 3 hourly sub-skin Sea Surface Temperature derived from Meteosat at 41.5° longitude, covering 60S-60N and 18.5W-101.5E and re-projected on a 0.05° regular grid, in GHRSST compliant netCDF format. The satellite input data has successively come from Meteosat at 41.5° longitude level 1 data processed at EUMETSAT. SST is retrieved from SEVIRI using a multi-spectral algorithm and a cloud mask. Atmospheric profiles of water vapor and temperature from a numerical weather prediction model, Sea Surface Temperature from an analysis, together with a radiative transfer model, are used to correct the multispectral algorithm for regional and seasonal biases due to changing atmospheric conditions.The quality of the products is monitored regularly by daily comparison of the satellite estimates against buoy measurements. The product format is compliant with the GHRSST Data Specification (GDS) version 2. Users are advised to use data only with quality levels 3, 4 and 5.

The Level-2 Ka-band Radar Interferometer (KaRIn) low rate (LR, ocean) sea surface height (SSH) data product from the Surface Water and Ocean Topography (SWOT) mission, also referenced by the short name L2_LR_SSH, provides ocean topography measurements from the low rate ocean data stream of the KaRIn instrument, spanning 60 km on either side of the nadir altimeter with a nadir gap. The L2_LR_SSH product is available continuously and globally, although different versions of the product may be produced at different latencies and/or through different reprocessing with refined input data. Note that L2_LR_SSH does not include SSH data from the SWOT nadir altimeter. The SWOT L2_LR_SSH product is organized in four files, the L2_LR_SSH ['Expert'] is described in this metadata sheet. The 3 other file types (['Basic'], ['WindWave'], ['Unsmoothed']) are described by 3 different metadata sheets that can be accessed via the links below. The ['Expert'] file is intended for expert users who are interested in the details of how the KaRIn measurements were derived and who may use detailed information for their own custom processing. The ['Basic'] file is intended for users who are interested in SSH measurements and who will use the KaRIn measurements as provided. The ['WindWave'] file is intended for users interested in wind and wave information. The ['Unsmoothed'] file, also intended for expert users, is provided on a finer 'native' grid of 250-m (with minimal smoothing applied), and has a significantly larger data volume than the other files. The ['Expert'] L2_LR_SSH includes copies of all variables in the Basic and WindWave files (sea surface height (SSH), sea surface height anomaly (SSHA), data quality flags, geophysical reference fields, height correction information, significant wave height (SWH), normalized radar cross section (NRCS or backscatter cross section or sigma0), wind speed derived from sigma0 and SWH, wind and wave model information, quality flags on a 2 km geographically fixed grid), plus more detailed information on the KaRIn instrument and environmental corrections, radiometer data, and geophysical models on a 2 km geographically fixed grid. May 2025: v3.0 (version D) Production and distribution of the L2_LR_SSH version D products: - PID0 for forward-processed version D products: from May 6, 2025 onward, - PGD0 for reprocessed version D products: from March 30 to July 10, 2023 (phase CalVal) and from July 26, 2023 to May 19, 2025 (phase Science) is ongoing. August 2024: v2.0 (version D) L2_LR_SSH version C products declared as validated by the SWOT project. March 2024: v2.0 (version C) Production and distribution of the pre-validated L2_LR_SSH version C products: - PIC0 for forward-processed version C products: November 23, 2023 to present, - PGC0 for reprocessed version C products: from March 30 to July 10, 2023 (phase CalVal) and from July 26, 2023 to January 25, 2024 (phase Science) November 2023: v1.0 The beta pre-validated L2_LR_SSH version 1.0 product (summer 2023 reprocessing release) is available only for the 1-day CalVal orbit phase, from March 29 to July 10, 2023, and the 21-day Science orbit phase from September 7 to November 21, 2023.