Nonequilibrium statistical mechanics of climate variability: modelling issues and applications to data assimilation techniques

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• Vanden-Eijnden, E (Courant Institute of Mathematical Sciences)
• Friday 01 November 2013, 12:20-12:55
• Seminar Room 1, Newton Institute.

If you have a question about this talk, please contact Mustapha Amrani.

Mathematics for the Fluid Earth

Stochastic models and computational tools for the study of transitions between different metastable states (or regimes) in climate system are discussed using the barotropic quasi-geostrophic (QG) equation as a test case. Specifically, a stochastic partial differential equation (SPDE) is obtained by adding appropriate forcing and damping terms to the QG equation to make this equation dynamically consistent with the predictions of equilibrium statistical mechanics, while allowing to study nonequilibrium phenomena such as transitions between different regimes. In the small noise regime, the most likely states of the invariant measure for this SPDE coincide with the selective decay states and we establish conditions under which these states are not unique, implying the existence of different climate regimes. We also analyze the mechanism and rate of the dynamical transitions between these regimes by computing the most likely paths connecting them. Finally we will discuss how the se results can be used in the context of data assimilation procedure based on Kalman or ensemble filters to improve the efficiency of these methods in the presence of regime shifts.

This talk is part of the Isaac Newton Institute Seminar Series series.

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