Performance and quality assessment of the forthcoming Copernicus Marine Service global ocean monitoring and forecasting real-time system

Jean-Michel Lellouche (Mercator Océan, France)

CoAuthors

Olivier Le Galloudec (Mercator Océan, France); Eric Greiner (CLS, France); Gilles Garric (Mercator Océan, France); Charly Régnier (Mercator Océan, France); Marie Drévillon (Mercator Océan, France); Yann Drillet (Mercator Océan, France)

Event: 2016 Ocean Surface Topography Science Team Meeting

Session: Application development for Operations

Presentation type: Type Oral

Mercator Ocean currently delivers in real-time daily services (weekly analyses and daily forecast) with a global 1/12° high resolution system. The model component is the NEMO platform driven at the surface by the IFS ECMWF atmospheric analyses and forecasts. Observations are assimilated by means of a reduced-order Kalman filter with a 3D multivariate modal decomposition of the forecast error. It includes an adaptive-error estimate and a localization algorithm. Along track altimeter data, satellite Sea Surface Temperature and in situ temperature and salinity vertical profiles are jointly assimilated to estimate the initial conditions for numerical ocean forecasting. A 3D-Var scheme provides a correction for the slowly-evolving large-scale biases in temperature and salinity.
Since May 2015, Mercator Ocean opened the Copernicus Marine Environment and Monitoring Service (CMEMS) and is in charge of the global eddy resolving ocean analyses and forecast. In this context, R&D activities have been conducted at Mercator Ocean these last years to improve the real-time 1/12° global system for the next CMEMS version in 2016. The ocean/sea-ice model and the assimilation scheme benefit of the following improvements: large-scale and objective correction of atmospheric quantities with satellite data, new Mean Dynamic Topography taking into account the last version of GOCE geoid, new adaptive tuning of some observational errors, new Quality Control on the assimilated temperature and salinity vertical profiles based on dynamic height criteria, assimilation of satellite sea-ice concentration, new freshwater runoff.
This presentation will show the impact of some updates separately, with a particular focus on adaptive tuning experiments of satellite Sea Level Anomaly (SLA) and Sea Surface Temperature (SST) observations errors. For the SLA, the a priori prescribed observation error is globally greatly reduced. The median value of the error changed from 5cm to 2.5cm in a few assimilation cycles. For the SST, we chose to maintain the median value of the error to 0.4°C. The spatial distribution of the SST error follows the model physics and atmospheric variability. Either for SLA or SST, we improve the performances of the system using this adaptive tuning. It allows us to have more realistic and evolutive observations errors maps which can provide valuable support to space agencies.
The overall behavior of the system integrating all updates reporting on the products quality improvements will be also discussed, highlighting the level of performance and the reliability of the new system.
 

Oral presentation show times:

RoomStart DateEnd Date
Richelieu Wed, Nov 02 2016,10:00 Wed, Nov 02 2016,10:15
Jean-Michel Lellouche
Mercator Océan
France
jlellouche@mercator-ocean.fr