Ocean Data Assimilation Systems for GODAE1

Ocean data assimilation has reached a sufficient level of maturity such that observations are routinely combined with model forecasts to produce a variety of ocean products. Approaches to ocean data assimilation vary widely, both in terms of the sophistication of the method and the observations assimilated, but also in terms of improving the details of the assimilation, such as forecast error covariances, model biases, observation representation errors, and quality control of the observations. In this paper we compare ocean data assimilation systems that have been developed within the GODAE community. We discuss the advantages and limitations of the methods and present practical aspects of the implementations, including observing systems used in the assimilation, specification of the error covariances, and analysis performance results. Finally, we describe plans for improving the systems in the post-GODAE time period beyond 2008. The GODAE systems discussed include: (1) Bluelink Ocean Data Assimilation System (BODAS), (2