Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/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
A revision of this discussion paper was accepted for the journal Geoscientific Model Development (GMD) and is expected to appear here in due course.
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., https://doi.org/10.5194/gmd-2017-22, in review, 2017.
Sylvain Delahaies et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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RC1: 'review', Anonymous Referee #1, 18 Apr 2017 Printer-friendly Version 
AC1: 'response to referee 1', S. Delahaies, 18 May 2017 Printer-friendly Version 
 
RC2: 'Review of Delahaies et al.', Anonymous Referee #2, 21 Apr 2017 Printer-friendly Version 
AC2: 'response to referee 2', S. Delahaies, 18 May 2017 Printer-friendly Version 
Sylvain Delahaies et al.

Model code and software

VAREC: a matlab package for Variational data assimilation for the DALEC model.
S. Delahaies
https://doi.org/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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