Normal forms for reduced stochastic climate models

Majda, Andrew J.; Franzke, Christian; Crommelin, Daan. 2009 Normal forms for reduced stochastic climate models. Proceedings of the National Academy of Sciences, 106 (10). 3649-3653. 10.1073/pnas.0900173106

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Abstract/Summary

The systematic development of reduced low-dimensional stochastic climate models from observations or comprehensive highdimensional climate models is an important topic for atmospheric low-frequency variability, climate sensitivity, and improved extended range forecasting. Here techniques from applied mathematics are utilized to systematically derive normal forms for reduced stochastic climate models for low-frequency variables. The use of a few Empirical Orthogonal Functions (EOFs) (also known as Principal Component Analysis, Karhunen–Loéve and Proper Orthogonal Decomposition) depending on observational data to span the low-frequency subspace requires the assessment of dyad interactions besides the more familiar triads in the interaction between the low- and high-frequency subspaces of the dynamics. It is shown below that the dyad and multiplicative triad interactions combine with the climatological linear operator interactions to simultaneously produce both strong nonlinear dissipation and Correlated Additive and Multiplicative (CAM) stochastic noise. For a single low-frequency variable the dyad interactions and climatological linear operator alone produce a normal form with CAM noise from advection of the large scales by the small scales and simultaneously strong cubic damping. These normal forms should prove useful for developing systematic strategies for the estimation of stochastic models from climate data. As an illustrative example the one-dimensional normal form is applied below to lowfrequency patterns such as the North Atlantic Oscillation (NAO) in a climate model. The results here also illustrate the short comings of a recent linear scalar CAM noise model proposed elsewhere for low-frequency variability.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1073/pnas.0900173106
Programmes:	BAS Programmes > Global Science in the Antarctic Context (2005-2009) > Natural Complexity Programme
ISSN:	1091-6490
Additional Information. Not used in RCUK Gateway to Research.:	An open access article
Additional Keywords:	Low-frequency teleconnection patterns, Nonlinearity, Correlated noise
NORA Subject Terms:	Atmospheric Sciences Mathematics
Date made live:	06 Apr 2009 14:13 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/6224

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