Development of a flexible data assimilation method in a 3D unstructured-grid ocean model under Earth System Modeling Framework

Abstract. We develop a new data assimilative (DA) approach by combining two parallel frameworks: a parallel DA framework (PDAF) and a flexible model coupling framework (ESMF). The new DA system is built on the ESMF at the top level that drives the PDAF and any combination of earth system modeling (ESM) components, to allow maximum flexibility and easy implementation of data assimilation for fully coupled ESM applications. We demonstrate the new DA system using a 3D unstructured-grid ocean model as ESM in this paper. The new system is validated using a simple benchmark and applied to a realistic case of Kuroshio simulation around Taiwan. The new system is demonstrated to significantly improve the model skill for temperature, velocity and surface elevation before, during and after typhoon events. The flexibility and ease of implementation make the new system widely applicable for other coupled ESMs.