Numerical aspects of applying the fluctuation dissipation theorem to study climate system sensitivity to external forcings

Abstract The fluctuation dissipation theorem (FDT), a classical result coming from statistical mechanics, suggests that, under certain conditions, the system response to external forcing can be obtained using the statistics of natural fluctuation of the system. The application of the FDT to the most...

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Bibliographic Details
Published in:Russian Journal of Numerical Analysis and Mathematical Modelling
Main Authors: Gritsun, Andrey, Branstator, Grant
Other Authors: Russian Science Foundation
Format: Article in Journal/Newspaper
Language:unknown
Published: Walter de Gruyter GmbH 2016
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Online Access:http://dx.doi.org/10.1515/rnam-2016-0032
http://www.degruyter.com/view/j/rnam.2016.31.issue-6/rnam-2016-0032/rnam-2016-0032.xml
https://www.degruyter.com/document/doi/10.1515/rnam-2016-0032/pdf
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Summary:Abstract The fluctuation dissipation theorem (FDT), a classical result coming from statistical mechanics, suggests that, under certain conditions, the system response to external forcing can be obtained using the statistics of natural fluctuation of the system. The application of the FDT to the most sophisticated climate models and the real climate system represents a difficult problem due to the huge dimensionality of these systems and the lack of the data available for proper sampling of the system natural variability. As a consequence, one has to use some regularization procedures constraining the form of permitted perturbations. Naturally, the skill of the FDT depends on the type and parameters of the regularization procedure. In the present paper we apply FDT to predict the response of a recent version of the NCAR climate system model (CCSM4) to salinity and temperature forcing anomalies in the North Atlantic. We study the sensitivity of our results to the amount of available data and to key parameters used in our numerical algorithm.