Open AccessWave–Mean Flow Interactions and the Maintenance of Superrotation in a Terrestrial Atmosphere
Author(s) -
João Rafael Dias Pinto,
Jonathan L. Mitchell
Publication year - 2016
Publication title -
journal of the atmospheric sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.853
H-Index - 173
eISSN - 1520-0469
pISSN - 0022-4928
DOI - 10.1175/jas-d-15-0208.1
Subject(s) - rossby wave , zonal flow (plasma) , mean flow , kelvin wave , baroclinity , rossby radius of deformation , barotropic fluid , atmosphere (unit) , equator , physics , extratropical cyclone , eddy , atmospheric sciences , atmospheric wave , geology , jet (fluid) , momentum (technical analysis) , jet stream , geophysics , atmospheric circulation , climatology , mechanics , wave propagation , meteorology , gravity wave , turbulence , latitude , plasma , astronomy , finance , quantum mechanics , economics , tokamak
The interplay between mean meridional circulation and transient eddies through wave–mean flow interaction processes defines the general behavior of any planetary atmospheric circulation. Under a higher-Rossby-number regime, equatorward momentum transports provided by large-scale disturbances generate a strong zonal flow at the equatorial region. At intermediate Rossby numbers, equatorial Kelvin waves play a leading role in maintaining a superrotating jet over the equator. However, at high Rossby numbers, the Kelvin wave only provides equatorward momentum fluxes during spinup, and the wave–mean flow process that maintains this strongly superrotating state has yet to be identified. This study presents a comprehensive analysis of the tridimensional structure and life cycle of atmospheric waves and their interaction with the mean flow, which maintains the strong, long-lived superrotating state in a higher-Rossby-number-regime atmosphere. The results show that the mean zonal superrotating circulation is maintained by the dynamical interaction between mixed baroclinic–barotropic Rossby wave modes via low-frequency variations of the zonal-mean state in short and sporadic periods of stronger instability. The modulation of amplitude of the equatorial and extratropical Rossby waves suggests a nonlinear mechanism of eddy–eddy interaction between these modes.