2004 LOM Workshop

Wednesday 11:20 - 11:40 a.m.

MULTIVARIATE DATA ASSIMILATION INTO HYCOM USING THE SEEK FILTER : IMPACT STUDIES

David Rozier, Florence Birol, Jean-Michel Brankart, Pierre Brasseur and Jacques Verron
LEGI, Grenoble, France
rozier@hmg.inpg.fr

ABSTRACT

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An integrated system for simulation of ocean circulation with data assimilation, has been developed at LEGI, as a result of the European DIADEM/TOPAZ projects. It is based on a 1/3º resolution North and Tropical Atlantic version of the HYCOM model. The assimilation scheme is a reduced-order Kalman filter derived from the Singular Evolutive Extended Kalman (SEEK) methodology. During the TOPAZ project, the SEEK assimilation scheme has been upgraded to incorporate in-situ measurements in addition to surface observations. The system is currently utilised in order to undertake various studies in the context of multivariate assimilation, whilst trying to understand better the mechanisms of assimilation and to pinpoint the current flaws of the methodology. A first set of studies examines the impact of various types of observations (sea-surface salinity data, mean dynamic topography, vertical temperature and salinity in situ profiles) within assimilation experiments. These impact studies illustrate particularly how sensitive the assimilation scheme is to quantitative and qualitative differences in the mean dynamic topography used in conjunction with observed sea-level anomalies. Secondly, experiments based on isolated observations are performed to understand better the assimilation mechanisms, identify any spurious effects such as artificially generated waves over large distances, and accordingly determine improvements of the assimilation method.

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LOM Users' Workshop, February 9-11, 2004