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Tropical Atmospheric Madden-Julian Oscillation: Strongly-Nonlinear Free Solitary Rossby Wave?

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Wednesday, 24 July 2019,

Wednesday, July 24, 2019. 12:00PM. Tropical Atmospheric Madden-Julian Oscillation: Strongly-Nonlinear Free Solitary Rossby Wave? Jun-Ichi Yano, Meteo France, Toulouse.  Sponsored by NOAA GFDL. More information here.

 

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 quasi--geostrophic 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 overall well with the observed MJO in scale and phase velocity within the factors.

Location  NOAA GFDL, Smagorinsky Seminar Room, Princeton University, Princeton, NJ.