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Performance of a 23-years TOPAZ reanalysis

Laurent Bertino, Francois Counillon, Jiping Xie
NERSC
(Abstract received 04/17/2015 for session X)
ABSTRACT

We will present a synthesis of the ice-ocean TOPAZ4 reanalysis for the period 1991-2013. TOPAZ4 is a modeling and data assimilation system based on the Nansen Center’s version of the HYCOM model (at horizontal resolution of about 12 km) and an Ensemble Kalman Filter (EnKF), integrating a dynamical ensemble of 100 members. The multivariate properties of the EnKF allow the TOPAZ system to assimilate several ocean and sea ice data types simultaneously, both in real-time forecasts applications (exploited operationally at MET Norway) and in reanalysis mode. The TOPAZ system constitutes the Arctic component of the MyOcean system (http://www.myocean.eu) and has been recently approved for the Copernicus Marine Environment Monitoring Services. The results from a 23-years reanalysis – the longest realistic EnKF run to our knowledge - show a good stability of the EnKF used in realistic settings and its ability to provide physically consistent error estimates for most variables assimilated, and only minor degradations compared to a model free run. The reanalysis also points to limitations of the sea ice model in terms of sea ice drift and motivates the further developments of new sea ice rheology models for the Marginal Ice Zone and the ice pack.

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2015 LOM Workshop, Copenhagen, Denmark June 2nd - 4th, 2015