Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
doi:10.5194/cp-2016-92
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
26 Sep 2016
Review status
A revision of this discussion paper is under review for the journal Climate of the Past (CP).
Assimilation of Pseudo-Tree-Ring-Width observations into an Atmospheric General Circulation Model
Walter Acevedo1, Bijan Fallah2, Sebastian Reich1, and Ulrich Cubasch2 1Institut für Mathematik, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
2Institut für Meteorologie, Freie Universität Berlin, Carl-Heinrich-Becker-Weg 6-10, 12165 Berlin, Germany
Abstract. We investigate the assimilation of Tree-Ring-Width (TRW) chronologies into an atmospheric global climate model using Ensemble Kalman Filter (EnKF) techniques and a process-based tree-growth forward model as observation operator. Our results, within a perfect-model experiment setting, indicate that the non-linear response of tree-growth to surface temperature and soil moisture does deteriorate the operation of the time-averaged (EnKF) methodology. Moreover, this skill loss appeared significantly sensitive to the structure of growth rate function, used to represent the Principle of Limiting Factors (PLF)s within the forward model. On the other hand, it was observed that the error reduction achieved by assimilating a particular pseudo-TRW chronology is modulated by the strength of the yearly internal variability of the model at the chronology site. This result might help the dendrochronology community to optimize their sampling efforts. In our experiments, the ''online'' (with cycling) paleao Data Assimilation (DA) approach did not outperform the ''offline'' (no-cycling) one, despite its considerable additional implementation complexity.

Citation: Acevedo, W., Fallah, B., Reich, S., and Cubasch, U.: Assimilation of Pseudo-Tree-Ring-Width observations into an Atmospheric General Circulation Model, Clim. Past Discuss., doi:10.5194/cp-2016-92, in review, 2016.
Walter Acevedo et al.
Walter Acevedo et al.
Walter Acevedo et al.

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Short summary
This study investigates several aspects of Palaeo-Data Assimilation (PDA): (i) we test the performance of several forward operators in the framework of a PDA-based climate reconstruction, (ii) compare the PDA-based simulations' skill against the free ensemble runs and (iii) investigate the skill of the "online" (with cycling) DA and the "off-line" (no-cycling) DA.
This study investigates several aspects of Palaeo-Data Assimilation (PDA): (i) we test the...
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