Tropical atmospheric Madden-Julian Oscillation: A strongly nonlinear free solitary Rossby wave?
The Madden-Julian oscillation (MJO), a planetary-scale eastward-propagating coherent structure with periods of 30-60 days, is a prominent manifestation of intraseasonal variability in the tropical atmosphere. It is widely presumed that small-scale moist cumulus convection is a critical part of its dynamics. However, the recent results from high-resolution modeling as well as data analysis suggest that the MJO may be understood by dry dynamics to a leading-order approximation. Simple, further theoretical considerations presented herein suggest that if it is to be understood by dry dynamics, the MJO is most likely a strongly nonlinear solitary Rossby wave. Under a global quasigeostrophic equivalent-barotropic formulation, modon theory provides such analytic solutions. Stability and the longevity of the modon solutions are investigated with a global shallow-water model. The preferred modon solutions with the greatest longevities compare well overall with the observed MJO in scale and phase velocity within the factors.
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http://n2t.net/ark:/85065/d7zp48sv
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2016-01-01T00:00:00Z
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2017-10-01T00:00:00Z
Copyright 2017 American Meteorological Society (AMS).
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