Testing variational estimation of process parameters and initial conditions of an earth system model

• Published in: Tellus. Series A, Dynamic meteorology and oceanography Vol. 66; no. 1; pp. 22606 - 15
• Main Authors: Blessing, Simon, Kaminski, Thomas, Lunkeit, Frank, Matei, Ion, Giering, Ralf, Köhl, Armin, Scholze, Marko, Herrmann, P., Fraedrich, Klaus, Stammer, Detlef
• Format: Journal Article
• Language: English
• Published: Stockholm Taylor & Francis 01.01.2014; Ubiquity Press; Stockholm University Press
• Subjects: adjoint model; Assimilation; Atmosphere; automatic differentiation; Biosphere; Carbon; Carbon cycle; climate modelling; coupled ocean-atmosphere model; Data assimilation; Derivatives; Dynamical systems; Dynamics; Earth; Earth and Related Environmental Sciences; earth system model; Geovetenskap och miljövetenskap; Initial conditions; Marine; Meteorology; Natural Sciences; Naturgeografi; Naturvetenskap; Ocean circulation; Parameter estimation; Physical Geography; Representations; Source code; Germany
• ISSN: 1600-0870; 0280-6495; 1600-0870
• DOI: 10.3402/tellusa.v66.22606

We present a variational assimilation system around a coarse resolution Earth System Model (ESM) and apply it for estimating initial conditions and parameters of the model. The system is based on derivative information that is efficiently provided by the ESM's adjoint, which has been generated through automatic differentiation of the model's source code. In our variational approach, the length of the feasible assimilation window is limited by the size of the domain in control space over which the approximation by the derivative is valid. This validity domain is reduced by non-smooth process representations. We show that in this respect the ocean component is less critical than the atmospheric component. We demonstrate how the feasible assimilation window can be extended to several weeks by modifying the implementation of specific process representations and by switching off processes such as precipitation.