10 March 2017

Rossby wave breaking and transient eddy forcing during Euro-Atlantic circulation regimes

Science

This study quantifies and diagnoses the role of Rossby wave breaking for the growth of persistent circulation patterns over the Euro-Atlantic region in an observational reanalysis and climate model simulations run at different resolutions.

Impact

This study finds that the Equator-ward movement of relatively cold air near the Atlantic jet stream that occurs during anticyclonic wave breaking acts to support jet extension just as much as the horizontal shift of momentum. Also, wave breaking and its role are simulated quite well in a climate model with a horizontal grid spacing of about 60 km, and running the model at a finer resolution does not result in a better representation.

Summary

Cyclonic and anticyclonic Rossby wave breaking (CWB and AWB, respectively) are identifiable by the overturning of large-scale atmospheric waves, particularly during the winter over the Euro-Atlantic region. CWB and AWB play crucial roles in modulating the passage of weather systems whose fluxes greatly impact the growth of persistent circulation patterns, or regimes. We quantify and diagnose the roles of CWB and AWB during the development of different circulation regimes using the ERA Interim Reanalysis as well as results from climate model simulations run at a range of horizontal resolutions. During development of a ridge of high pressure (often related to blocked flow), we find that despite a strong linkage with AWB, AWB-related fluxes actually work against ridge growth. We also find that the Equator-ward movement of relatively cold air near the Atlantic jet stream associated with AWB acts to support jet extension just as much as the horizontal shift of momentum. The representation and role of wave breaking is simulated quite well and not improved further by increasing resolution (grid mesh finer than about 60 km).

Contact
Erik T Swenson
George Mason University