Over the last few decades an ever increasing amount of observational data of the global ocean have been collected. At the same time the development of global ocean models has also been steadily progressing. A data assimilation system aims to estimate a state of the ocean that is consistent with both a set of observations and a model.
Estimation the Circulation and Climate of the Ocean (ECCO) is a consortium that intends to bring ocean state estimation from its current experimental status to that of a practical and quasi-operational tool for studying large-scale ocean dynamics, designing observational strategies, and examining the ocean's role in climate variability" (see Stammer et al. 1999). The consortium is formed by oceanographers at three American Institutions: ( Scripps Institution of Oceanography , the Jet Propulsion Laboratory , and the Massachusetts Institute of Technology )
Ralf has played a key role in this project from the very beginning. He has worked simultaneously on many tasks, such as: automatic differentiation of the model code, sensitivity analysis using the adjoint model, variational data assimilation, determination of the uncertainty structure in the derived ocean state, parallelisation of the direct pressure solver, and Kalman-filter state transition matrix computation by means of the automatically generated tangent linear code.
Previous to this, Ralf developed a data assimilation system at the Max-Planck-Institute in Hamburg. The system is based on the Hamburg Large Scale Geostrophic Ocean General Circulation Model by Ernst Maier-Reimer and its adjoint, which was coded by Ralf. The data assimilation system is still in use at the Max-Planck-Institute in Hamburg and the Alfred-Wegener-Institute at Bremerhaven. Meanwhile, there are a number of further references on adjoints of ocean models generated by TAMC and TAF.