Evaluation of the atmospheric pressure effects in the future Mercator Ocean global 1/4° configuration.
Evaluation of the atmospheric pressure effects in the future Mercator Ocean global 1/4° configuration.
Abstract:
In the framework of Copernicus Marine environment monitoring service, Mercator Ocean, the French center for ocean forecasting, develops and operates several operational forecasting systems (a model with an assimilation system). This year, we have developed, conjointly with other European research teams, a new version of the global 1/4° model. This new configuration will be use in our next reanalysis products, ensemble products and will be the high-resolution configuration for the next IPCC exercise for different European institutions. The major changes compare to the old one are: a grid extended to the South Pole, the last version of NEMO code coupled with LIM3 ice model, time splitting algorithm to compute surface pressure gradient and z* vertical coordinate.
To validate this new configuration, an inter-annual experiments, in forced mode (without assimilation), over last decades, has been performed. This experiment is driven by ECMWF re-analyses ERAinterim. In same time, a twin experiment, where atmospheric pressure has been taking into account, has been preformed. The atmospheric pressure impacts the computation of the pressure gradient and modifies locally the relative humidity.
In this presentation, after a description of the simulations, we focus first on the global scale impact. The balance evaporation minus precipitations of the simulation with atmospheric pressure is stronger and correlated with the large-scale pressure variations. Then, we show the changes in term of variability:
• of the Sea Surface Height, which are located at high latitudes in agreement with the variations of the pressure field. A harmonic analysis highlights the response of the ocean to the pressure with the signature of the harmonics S1 and S2.
• of the transport in some key straits as Gibraltar where the hydraulic control between basins drive this phenomenon.
To validate this new configuration, an inter-annual experiments, in forced mode (without assimilation), over last decades, has been performed. This experiment is driven by ECMWF re-analyses ERAinterim. In same time, a twin experiment, where atmospheric pressure has been taking into account, has been preformed. The atmospheric pressure impacts the computation of the pressure gradient and modifies locally the relative humidity.
In this presentation, after a description of the simulations, we focus first on the global scale impact. The balance evaporation minus precipitations of the simulation with atmospheric pressure is stronger and correlated with the large-scale pressure variations. Then, we show the changes in term of variability:
• of the Sea Surface Height, which are located at high latitudes in agreement with the variations of the pressure field. A harmonic analysis highlights the response of the ocean to the pressure with the signature of the harmonics S1 and S2.
• of the transport in some key straits as Gibraltar where the hydraulic control between basins drive this phenomenon.