A Linear Stochastic Model of a GCM’s Midlatitude Storm Tracks

A linear stochastic model is used to simulate the midlatitude storm tracks produced by an atmospheric GCM. A series of six perpetual insolation/SST GCM experiments are first performed for each month. These experiments capture the ‘‘midwinter suppression’’ of the Pacific storm track in a particularly clean way. The stochastic model is constructed by linearizing the GCM about its January climatology and finding damping and stirring parameters that best reproduce that model’s eddy statistics. The model is tested by examining its ability to simulate other GCM integrations when the basic state is changed to the mean flow of those models, while keeping the stirring and damping unchanged. The stochastic model shows an impressive ability to simulate a variety of eddy statistics. It captures the midwinter suppression of the Pacific storm track qualitatively and is also capable of simulating storm track .

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