Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
doi:10.5194/gmd-2017-22
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Development and technical paper
10 Feb 2017
Review status
This discussion paper is under review for the journal Geoscientific Model Development (GMD).
Constraining DALEC v2 using multiple data streams and ecological constraints: analysis and application
Sylvain Delahaies1, Ian Roulstone1, and Nancy Nichols2 1Department of Mathematics, University of Surrey, Guildford, UK
2Department of Mathematics, University of Reading, Reading, UK
Abstract. We use a variational method to assimilate multiple data streams into the terrestrial ecosystem carbon cycle model DALECv2. Ecological and dynamical constraints have recently been introduced to constrain unresolved components of this otherwise ill-posed problem. Here we recast these constraints as a multivariate Gaussian distribution to incorporate them into the variational framework and we demonstrate their benefit through a linear analysis. Using an adjoint method we study a linear approximation of the inverse problem: firstly we perform a sensitivity analysis of the different outputs under consideration, and secondly we use the concept of resolution matrices to diagnose the nature of the ill-posedness and evaluate regularisation strategies. We then study the non linear problem with an application to real data. Finally, we propose a modification to the model: introducing a spin-up period provides us with a built-in formulation of some ecological constraints which facilitates the variational approach.

Citation: Delahaies, S., Roulstone, I., and Nichols, N.: Constraining DALEC v2 using multiple data streams and ecological constraints: analysis and application, Geosci. Model Dev. Discuss., doi:10.5194/gmd-2017-22, in review, 2017.
Sylvain Delahaies et al.
Sylvain Delahaies et al.

Model code and software

VAREC: a matlab package for Variational data assimilation for the DALEC model.
S. Delahaies
doi:10.5281/zenodo.269937
Sylvain Delahaies et al.

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Short summary
Carbon is a fundamental constituent of life and understanding its global cycle is a key challenge for the modeling of the Earth system. We use a variational method to estimate parameters and initial conditions for the carbon cycle model DALECv2 using multiple sources of observations. We develop a methodology that helps understanding the nature of the inverse problem and evaluating solution strategies, then we demonstrate the efficiency of the variational method in an experiment using real data.
Carbon is a fundamental constituent of life and understanding its global cycle is a key...
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