ESRL/PSD Seminar Series

North Pacific Jet Retractions: Dynamical Mechanisms and Contributions from Midlatitude and Tropical Forcing

Melissa Breeden
Postdoctoral Research Associate Cooperative Institute for Meteorological and Satellite Studies University of Wisconsin-Madison


This talk will overview the literature and ongoing work geared towards understanding North Pacific jet variability, and specifically the breakdown of the strong North Pacific jet into wavy, blocked flow in boreal winter. The processes associated with this zonal retraction of the jet are first explored through case studies (one presented here), with an emphasis on barotropic and nonlinear effects. Quasi-geostrophic potential vorticity tendencies are invoked to quantify the contributions from these distinct mechanisms, and a novel extension of this method is introduced to diagnose geostrophic zonal wind tendencies in a piecewise manner. It is found in the case presented (and in others) that nonlinear interactions retract the jet, and the context in which this occurs is conducive to barotropic energy extraction by eddies from the jet itself. Jet retractions are then modeled using a linear inverse model, inferring the dynamics that drive retractions from an empirical atmospheric operator obtained from time-lagged analysis covariance. The optimal initial structures that precede retraction in the model are derived, followed by examination of the relative contributions from the tropics and midlatitudes. The features identified in the case study will be compared with those determined by the LIM, each approach complementing the results of the other. Discussion of future applications of the methods presented will conclude the presentation.

Wednesday Oct 31, 2018
2:00 pm
Seminar Coordinator: Maddie Sturgill (

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