CMEMS - Sealevel GLO PHY L4 observations 008 047

WORK IN PROGRESS!!!!

 

SEALEVEL_GLO_PHY_L4_MY_008_047 is a satellite global sea level product downloaded from the Copernicus Marine Environment Monitoring Service (CMEMS). This product was known as SEALEVEL_GLO_PHY_L4_REP_OBSERVATIONS_008_047 until December 2021 when the current version, DT-2021,  was introduced with a new name. Different evolutions have been introduced in the altimeter standards and processing methods used. A full description of the changes implemented is available in the QUID document (section V.4.1).

 

For more information and the official documentation, including the product manual refer to the CMEMS data portal.

 

Altimeter satellite gridded Sea Level Anomalies (SLA) computed with respect to a twenty-year 2012 mean. The SLA is estimated by Optimal Interpolation, merging the measurement from the different altimeter missions available (see QUID document or 1 [[[|http://duacs.cls.fr]]] pages for processing details). The product gives additional variables (i.e. Absolute Dynamic Topography and geostrophic currents (absolute and anomalies)). This product is processed by the DUACS multimission altimeter data processing system. It serves in near-real time the main operational oceanography and climate forecasting centers in Europe and worldwide. It processes data from all altimeter missions: Jason-3, Sentinel-3A, HY-2A, Saral/AltiKa, Cryosat-2, Jason-2, Jason-1, T/P, ENVISAT, GFO, ERS1/2. It provides a consistent and homogeneous catalogue of products for varied applications, both for near real time applications and offline studies. To produce maps of Sea Level Anomalies (SLA) and Absolute Dynamic Topography (ADT) in delayed-time (REPROCESSED), the system uses the along-track altimeter missions from products called SEALEVEL_*PHY_L3_MY_008*. Finally an Optimal Interpolation is made merging all the flying satellites in order to compute gridded SLA and ADT. The geostrophic currents are derived from sla (geostrophic velocities anomalies, ugosa and vgosa variables) and from adt (absolute geostrophic velicities, ugos and vgos variables). Note that the gridded products can be visualized on the LAS (Live Access Data) Aviso+ web page (2 [[1] http://www.aviso.altimetry.fr/en/data/data-access/las-live-access-server.html]]).

 

We still have the SEALEVEL_GLO_PHY_L4_REP_OBSERVATIONS_008_047 latest versions. These were previously distributed by Aviso+, and are occasionally still refer as such. All the missions were homogenized with respect to a reference mission which was OSTM/Jason-2 for v2019. The sla is computed with an optimal and centered computation time window (6 weeks before and after the date). Resolution is 0.25X0.25 degrees and has an irregular temporal resolution. The data starts in 1993 and ends in June 2020.

Terms of use

NB You need to register with CMEMS to use this product:

Registration form: http://marine.copernicus.eu/web/56-user-registration-form.php .

The full terms are listed on the CMEMS website: http:marine.copernicus.eu/services-portfolio/service-commitments-and-licence/#licence

In particular: ... In case of any publication, the Licensee will ensure credit the Copernicus Marine Service in the following manner:“This study has been conducted using E.U. Copernicus Marine Service Information” ...

On NCI

This dataset is available in the ua8 project:

/g/data/ua8/CMEMS_SeaLevel/<version>/<year>/<files>

v2019 is the most recent version

Filenames are:

dt_global_allsat_phy_l4_YYYYMMDD_<production_date>.nc

Variables:

• sea_surface_height_above_sea_level (SSH)
• surface_geostrophic_eastward_sea_water_velocity_assuming_sea_level_for_geoid (UVG)
• surface_geostrophic_northward_sea_water_velocity_assuming_sea_level_for_geoid (UVG)
• sea_surface_height_above_geoid (SSH)
• surface_geostrophic_eastward_sea_water_velocity (UVG)
• surface_geostrophic_northward_sea_water_velocity (UVG)

Timeseries

The "timeseries" folder contains a concatenated version of the dataset latest version (v2019). Each year is concatenated in one file and chunksizes have been changed to make accessing the data as a timeseries faster. We try to update the current year regularly but still there might be more days available in the actual datset folder (v2019).

 

Updates

2021-10-20 There hasn't been updates to this dataset for a while, the latest available data is 2020-06-03. We check for updates regularly, so we when updates will resume we will be downloading the new data automatically.

2020-07-17 We updated to the most recent version v2019. As CMEMS doesn't always distinguish between a new version and an extension the year 2018/2019 were previously incorrectly downloaded as part of v4-0 while they are available now in v2019.

For more information check the CMEMS release notes