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Interpreting the upper level structure of the Madden‐Julian oscillation
Author(s) -
Monteiro Joy M.,
Adames Ángel F.,
Wallace John M.,
Sukhatme Jai S.
Publication year - 2014
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl062518
Subject(s) - rossby wave , zonal flow (plasma) , potential vorticity , zonal and meridional , madden–julian oscillation , physics , advection , oscillation (cell signaling) , kelvin wave , vorticity , geology , meridional flow , equatorial waves , atmospheric sciences , flow (mathematics) , geophysics , climatology , mechanics , meteorology , convection , vortex , latitude , plasma , astronomy , genetics , equator , quantum mechanics , biology , tokamak , thermodynamics
The nonlinear response of a spherical shallow water model to an imposed heat source in the presence of realistic zonal mean zonal winds is investigated numerically. The solutions exhibit elongated, meridionally tilted ridges and troughs indicative of a poleward dispersion of wave activity. As the speed of the jets is increased, the equatorial Kelvin wave is unaffected but the global Rossby wave train coalesces to form a compact, amplified quadrupole structure that bears a striking resemblance to the observed upper level structure of the Madden‐Julian oscillation. In the presence of strong subtropical westerly jets, the advection of planetary vorticity by the meridional flow and relative vorticity by the zonally averaged background flow conspire to create the distinctive quadrupole configuration of flanking Rossby waves.