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SUMMARY:Nonequilibrium statistical mechanics of climate variability: model
 ling issues and applications to data assimilation techniques - Vanden-Eijn
 den\, E (Courant Institute of Mathematical Sciences)
DTSTART:20131101T122000Z
DTEND:20131101T125500Z
UID:TALK48649@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Stochastic models and computational tools for the study of tra
 nsitions between different metastable states (or regimes) in climate syste
 m 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 eq
 uation to make this equation dynamically consistent with the predictions o
 f equilibrium statistical mechanics\, while allowing to study nonequilibri
 um phenomena such as transitions between different regimes. In the small n
 oise regime\, the most likely states of the invariant measure for this SPD
 E coincide with the selective decay states and we establish conditions und
 er 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 conne
 cting 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 shif
 ts.\n
LOCATION:Seminar Room 1\, Newton Institute
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