Abstract's details

Toward a community global 1/36° configuration based on NEMO

Perrine Abjean (Mercator Ocean International, France)


Clément Bricaud (Mercator Ocean International, France); Jérome Chanut (Mercator Ocean International, France); Romain Bourdalle-Badie (Mercator Ocean International, France); Gilles Garric (Mercator Ocean International, France); Théo Brivoal (Mercator Ocean International, France)

Event: 2022 Ocean Surface Topography Science Team Meeting

Session: Tides, internal tides and high-frequency processes

Presentation type: Type Oral

In the framework of the Copernicus Marine Environment Monitoring Service, Mercator Ocean International operates a global high-resolution forecasting systems at the resolution of 1/12°. Increasing resolution appears necessary to improve the quality of service and to satisfy the users’ requests in the operational application (Le Traon, 2019). Resolving scales below 100 kilometers, and in particular sub mesoscale processes (1-50 km), appears to be essential to better represent the circulation in the open ocean (Chassignet, 2017), and, in particular to improve the large-scale representations thanks to a more explicit energy transfers between finer and larger scales (Fox-Kemper Baylor, 2019). A deeper understanding of their various contributions (geostrophic flows, tidal motions, waves, inertial currents) and their role in the global ocean kinetic energy budget will improve the knowledge of these energy transfers between different scales.

With the multiplication of observing platforms and the enhancement of their accuracy, the time and space resolution of observations have been improved. The description of finer scales has since been significantly improved. It is now estimated that the present and future observation platforms will be able to deliver data at scales finer that 50 km. SWOT (https://swot.jpl.nasa.gov/science.html) will allow observing scales until 15 to 30 km whereas actual altimeters are limited to 150 km (Morrow 2019). These new missions could also provide ocean currents at a resolution from 70 km at high latitude to 250 km at the equator. However, the current status of numerical models routinely operated for analysis and forecasts, are not adapted for digesting measurements coming from such new generations of sensors.

In 2019, it has been decided to go towards higher resolution and develop a new global sub mesoscale-permitting model. Benefiting from the context of the European H2020 IMMERSE project, a new 1/36° global configuration (resolution of 3 km at the equator and 1km close to the pole), based on the NEMO 4 OGCM has been developed. Thanks to the resolution increase, this model can resolve the Rossby radius in almost all open oceans areas at global scale quite everywhere and to span a large part of the internal wave spectrum. This model is driven at the surface by the 1H ECMWF IFS system. Tidal forcing with 5 components (K1, O1, S2, M2, N2) and atmospheric pressure forcing have been activated.

First, based on a hierarchy of simulations at 1/4°, 1/12° and 1/36° and with/without explicit tide representation, we propose a first evaluation of the benefits due to the resolution increase and tidal forcing. Circulation, energy, tidal representation and mixing of the experiments are compared to each other’s.

A long multi-year experiment performed with the global 1/36° configuration is in preparation and will be described. 3D hourly outputs will be stored and data will be available through cloud facilities. This experiment is also planned to be used in OSSE framework (Observing System Simulation Experiment).

Oral presentation show times:

Room Start Date End Date
Sala Pasinetti Wed, Nov 02 2022,15:15 Wed, Nov 02 2022,15:30
Perrine Abjean
Mercator Ocean International