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What is the difference between the Mercator Ocean Service and the Copernicus Marine Service?

Both services are provided by Mercator Ocean.

The Mercator Ocean Service offers customised oceanography services as part of its French public-service mission.

The Copernicus Marine Service (CMS) offers an off-the-shelf oceanography service. This is a European public service proposed by Mercator Ocean, which was selected and then delegated by the European Commission to operate the service. Mercator Ocean is also a supplier of numerical modelling products of the global ocean for the Copernicus Marine Service.

The products created by Mercator Ocean are distributed (exclusively) by the Copernicus Marine Service or the Mercator Ocean Service. This means that the Mercator Ocean products included in the Copernicus Marine Service catalogue are only available via the Copernicus Marine Service, and also that the products and services offered by Mercator Ocean are only accessible via the Mercator Ocean Service.

The Mercator Ocean Service offers customised oceanography services:

  • Mercator Ocean offers through its expertise a service for oceanographic products for the global ocean. These numerical modelling products cover all seas around the globe, from the surface to the seabed, at horizontal resolutions of between 1/36° and 1°, depending on the geographical area. They include physical, biological, and ice parameters, mostly since the beginning of the 1990s up to now, as well as 7-day forecasts.
  • Do you need oceanography expertise? Specific products? In special formats? With certain variables? Covering a particular period? Of a given ocean layer? … You are developing products concerning:
  • Please use this online form to describe your needs and expectations in a few lines; we will get back to you as soon as possible.
  • Please be aware that the Mercator Ocean Service is open to all, but that rights and access differ depending on the users and uses. Find out more.
  • For any questions, please contact products@mercator-ocean.fr

The Copernicus Marine Service offers a catalogue-based oceanography service:

  • The Copernicus Marine Service offers a wide selection of oceanography products, ranging from observation products (using satellite and in-situ data), to numerical modelling products. These different products, listed in a single catalogue, cover the global ocean and the six European basins: the Arctic, Baltic, North-East Atlantic (northern and southern parts), Mediterranean and the Black Sea. Whether from observation or from models, the products include both physical and biogeochemical parameters and extend over long time periods going back to the beginning of the 1990s, sometimes earlier, and including near real time for observation products, with forecasting covering several days for products generated by models.
  • The products are created by various European producers and distributed by the Copernicus Marine Service via an online catalogue.
  • You can choose the products in which you are interested from the Copernicus Marine Service’s online catalogue and download them (registration required for the first download).
  • The Copernicus Marine Service is open and free to any user and for any use in compliance with the conditions of use
  • For any question, please contact servicedesk.cmems@mercator-ocean.eu post your question on the forum.

What is the difference between the products distributed by the Mercator Ocean Service and those from the Copernicus Marine Service?

The Mercator Ocean Service only offers products generated from numerical models.

The Copernicus Marine Service offers products generated from both numerical models and in-situ or satellite observation data.

Mercator Ocean Service’s reference products are described in the following table.

The products of the Copernicus Marine Service are available here.

What is a product produced from a numerical model?

It is the product of a mathematical ocean model governed by equations from fluid dynamics, known as “primitive equations” (e.g. NEMO-OPA). These numerical equations are resolved by millions of calculations on super-computers. Observation data are then assimilated in the model, i.e. the results of the mathematical model are combined with observation data (e.g. from satellites or in-situ buoys) in order to generate the most realistic possible final representation of the ocean state. This also makes it possible to provide 7-day forecasts of the ocean state. A numerical model therefore enables forecasters to provide a three-dimensional representation, current, past or future, of the ocean’s physical or biogeochemical state.

Both the Mercator Ocean Service and the Copernicus Marine Service offer products generated by numerical models:

Mercator Ocean Service’s reference products are described in the following table.

The products of the Copernicus Marine Service are available here.

What is a product produced from satellite or in-situ observations?

An observation product is generated directly by using raw data from satellite and in-situ observations, after scientific validation and calibration. These results are also sometimes smoothed and interpolated with other data in order to make the product more readable and with broader geographical coverage.

Only the Copernicus Marine Service offers products produced from in-situ or satellite observations.

The products of the Copernicus Marine Service are available here.

What is a numerical product?

It is a set of data files generated by a numerical model or from satellite or in-situ observations, containing a set of ocean variables, describing the physical or biogeochemical state of the ocean at the global or regional scale, both on the surface and at depth, currently, in the past or in the future. A product may also be a map, representing the ocean state.

Mercator Ocean Service’s reference products are described in the following table.

The products of the Copernicus Marine Service are available here.

What time periods do these products cover?

The products are divided into two categories, whether for Mercator Ocean or the Copernicus Marine Service:

  • NEAR REAL TIME products are those that represent the recent state of the ocean and which are updated regularly (every day or every week).
  • MULTIYEAR TIME SERIES products represent the state of the ocean in the past (typically within the previous 20 years) and are not updated regularly but only once a year.

Mercator Ocean Service’s reference products are described in the following table.

The products of the Copernicus Marine Service are available here.

What geographical areas do these products cover?

The Mercator Ocean Service covers three geographical regions:

  • The global ocean: all the oceans and major seas of the globe (180°W-180°E; 80°S-90°N).
  • The southern part of the Northeastern Atlantic Ocean and the Western Mediterranean Sea up to the east of Corsica (20°W-10°E; 26°N-64°N).
  • The Mediterranean Sea (11°W-37°E; 30°N-46°N).

The Copernicus Marine Service covers six geographical regions:

  • The global ocean: all the oceans and major seas of the globe (180°W-180°E; 80°S-90°N).
  • The northern part of the Northeastern Atlantic Ocean (20°W-13°E; 48°N-62°N).
  • The southern part of the Northeastern Atlantic Ocean and the Western Mediterranean up to the east of Corsica (20°W-10°E; 26°N-56°N).
  • The Mediterranean (11°W-37°E; 30°N-46°N).
  • The Baltic
  • The Arctic Ocean
  • The Black Sea to the Bosphorus

Mercator Ocean Service’s reference products are described in the following table.

The products of the Copernicus Marine Service are available here.

What is a grid?

A grid is a mesh composed of two (or more) sets of curves, each set intersecting the other according to an algorithm.

In most cases, one of two types of grid are used:

The Native Grid is the one on which the ocean fields of the numerical model are calculated (e.g. the ARAKAWA C grid). There are no interpolations. This Native Grid offers the advantage of exactly representing what the system has calculated, but with the drawback that it is difficult to manipulate as all the variables are not located on the same node of the grid (i.e. they are “staggered”) and the lines running from the North Pole to the South Pole in the system do not correspond to the lines of the traditional geographic meridians (which are “stretched” and “rotated”).

The Standard Grid is the one on which the ocean fields initially calculated on a Native Grid are interpolated. It is simpler to use and easier to manipulate. All variables are located on the same node. It uses a cylindrical equidistant projection, for example. As an illustration, the oceanic currents expressed by U and V on the Standard Grid no longer depend on the grid and correspond to conventional zonal and meridional currents. In addition, the interpolated Standard Grid is suitable for sampling eddies. Eddies are thus correctly represented on the interpolated Standard Grid.

Which variables are provided?

For the Mercator Ocean Service:

  • The variables concerning ocean physics are mainly the ocean potential temperature, ocean salinity, sea level, ocean currents, and the concentration, thickness and drift of sea ice. Other variables may be available.
  • The variables concerning ocean biogeochemistry are mainly for chlorophyll, nitrates, phosphates and oxygen, as well as phytoplankton carbon biomass and primary production. Other variables may be available.

For the Copernicus Marine Service:

  • The variables for ocean physics are: potential temperature (for models or satellite and in-situ observations), salinity, currents, Stokes drift (current due to waves), sea surface height, geopotential height, sea ice (concentration, thickness, drift, surface temperature, iceberg density, ice type, ice boundaries, etc.), depth of the mixed layer, radiative fluxes and winds.
  • The variables for ocean biogeochemistry are: nitrates, phosphates, primary production, silicate, phytoplankton, zooplankton, depth of the euphotic layer, chlorophyll, dissolved oxygen, dissolved iron, optical properties of sea water, dissolved ammonium.

How often are these products updated?

The frequency varies according to the product: a product may be updated several times per day, or once a day, once a week, once a year, etc.

What are the names given to the different estimates of ocean states, past, present or future?

Ocean Forecast: Output from an ocean model to predict the future state of the ocean for periods from 1 day to 14 days ahead. Ocean Forecast products are updated weekly or daily, depending on the ocean model concerned.

Ocean Analysis: Output from an ocean model giving the best possible estimate of the recent and present ocean state. These results are aggregated in time, making up time series that are updated and incremented with the latest results either daily or weekly, depending on the ocean model concerned. These analyses represent ocean states that are almost simultaneous with the present time.

Ocean Reanalysis: Output from an ocean model giving the best possible estimate of a past ocean state. These results are derived from a dedicated numerical ocean model, forced by and assimilating consistent reprocessed observations acquired in-situ and by satellite. Reanalysis products display a time series in the past which is at least 20 years long.

A Non-Assimilative Hindcast is a time series in the past, at least 20 years long, into which no data have been assimilated (unlike ocean reanalysis).

What is data assimilation?

In meteorology, data assimilation involves using actual observations to correct a forecast of the state of the atmosphere. Likewise, assimilation in physical oceanography data is the mathematical process of using actual observations (from satellites or in-situ) to correct a forecast of the state of the ocean in order to produce an analysis of the ocean state.

The SEEK-SAM2 method for sequential reduced-order data assimilation (the Mercator Ocean data assimilation system version 2) was developed by Mercator Ocean and is used in most operational Mercator systems. This pattern of assimilation enables the optimum combination of observations and forecasts by ocean models to be achieved for producing an ocean analysis. This analysis is deemed to provide the most probable representation of an ocean state taking into account both the available observations and the forecast. The SAM2 method is a reduced-order Kalman filter based on the SEEK formulation (Singular Scalable Extended Kalman). The solution that minimizes the least-squares deviation between observations and their equivalent model is calculated in a reduced space, in the form of a linear combination of the model’s error modes. The calculated correction, known as the increment, is applied progressively to all or part of the assimilation window to limit the initialisation shock at the instant the corrected model is restarted (Incremental Analysis Update).

Which format is used for numerical files?

NetCDF (Network Common Data Form) is a data format containing its own metadata (and thus independent of the hardware used), enabling the creation, accessibility and sharing of scientific data stored in table form.

All Mercator Ocean numerical files are in NetCDF-3 format, using the CF convention.

How are products delivered?

For the Mercator Ocean Service:

  • Mercator Ocean website: http://www.mercator-ocean.fr/en/
  • Email: email is a service for the transmission of written messages and documents sent electronically via a computer network (the internet).
  • Cloud: the cloud is a way of using the power of computing or storage on remote servers over a network (the internet).
  • FTP: the File Transfer Protocol, or FTP, is a communication protocol for exchanging computer files over a TCP/IP network. It enables files to be copied from one computer to another.
  • External drive: delayed data can be delivered to users via an external drive. This alternative should be used rather than the FTP option when the data are too voluminous for Internet transfer, or depending on user constraints. The choice of medium depends on i) the volume to be transferred, ii) the physical formats that the user is equipped to read. The portable hard disk is recommended.

For the Copernicus Marine Service:

You can choose the products in which you are interested from the Copernicus Marine Service’s online catalogue and download them (registration required for the first download). The Copernicus Marine Service is open and free to any user and for any use in compliance with the conditions of use.

What tools do I need to manipulate these products?

  • A- Definition

What is the NetCDF format?

http://www.unidata.ucar.edu/software/netcdf/

Go to a list of tools for manipulating or displaying NetCDF data:

http://www.unidata.ucar.edu/software/netcdf/software.html

Here are samples of NetCDF files of Mercator Ocean products:

  •  B- Decompression (non exhaustive list)

Bzip2 decompressor (Windows : http://www.7-zip.org/) or pages of the Bzip2 project: http://www.bzip.org/

  •  C- Visualisation (non-exhaustive list of tools for viewing, that are easy to install)

Ncview http://meteora.ucsd.edu/~pierce/ncview_home_page.html

Visualisation and first-level analysis (easy to install on Unix/Linux platforms, possible under Windows)

Ferret http://ferret.wrc.noaa.gov/Ferret/

Viewing and advanced analysis (you need to develop your own program)

Matplotlib, python library http://matplotlib.sourceforge.net/

ncl http://www.ncl.ucar.edu

idv http://www.unidata.ucar.edu/software/idv/ Visualisation avancée avec animation 3D

  •  D- Extraction/Manipulation

Concatenation/Computing the mean/Adding variables and attributes, etc. (non-exhaustive list)

List of software for manipulating NetCDF, http://www.unidata.ucar.edu/software/netcdf/software.html

The NetCDF software package, which includes libraries for Fortran and C++, can be downloaded for free, please see: http://www.unidata.ucar.edu/software/netcdf/docs/faq.html#howtoget.

This coding package offers the best performance for manipulating files in NetCDF format, including conversion to ASCII and other formats.

The NCO operators constitute a powerful set of tools (for Extraction/Concatenation/Computing the mean/Adding variables and attributes) for working with NetCDF files. They can be obtained free of charge from  http://nco.sourceforge.net/

cdo https://code.zmaw.de/projects/cdo

Marine Geospatial Ecology Tools http://code.env.duke.edu/projects/mget

This is a free add-on to ArcGIS, used to convert formats such as NetCDF into ASCII and ArcGrid.

  •  E- Conversion (from NetCDF format to GRIB for example)

ncl http://www.ncl.ucar.edu