Identification

Title

A nonlinear perspective on the dynamics of the MJO: Idealized large-eddy simulations

Abstract

The 30-60-day intraseasonal atmospheric oscillation in the equatorial atmosphere, the Madden-Julian oscillation (MJO), is most visible in its signature of outgoing longwave radiation and associated convective centers. Diabatic processes related to tropical convection and two-way atmosphere-ocean interaction are hence generally believed to be crucial in explaining the origin of the MJO phenomenon. However, reliable deterministic forecasting of the MJO in global circulation models and understanding its mechanism remains unsatisfactory. Here a different approach is taken, where the hypothesis is tested that eastward-propagating MJO-like structures originate fundamentally as a result of nonlinear (dry) Rossby wave dynamics. A laboratory-scale numerical model is constructed, where the generation of solitary structures is excited and maintained via zonally propagating meanders of the meridional boundaries of a zonally periodic β plane. The large-eddy simulations capture details of the formation of solitary structures and of their impact on the convective organization. The horizontal structure and the propagation of anomalous streamfunction patterns, a diagnostic typically used in tracing the equatorial MJO, are similar to archetype solutions of the Korteweg-deVries equation, which extends the linear shallow water theory—commonly used to explain equatorial wave motions—to a weakly nonlinear regime for small Rossby numbers. Furthermore, the characteristics of the three-dimensional laboratory-scale numerical results compare well with observed features of the equatorial MJO and thus the study provides indirect evidence of the basic principles underlying the wave-driven eastward propagation of the MJO.

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document

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http://n2t.net/ark:/85065/d7057gbs

codeSpace

Dataset language

eng

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geoscientificInformation

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title

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publication

effective date

2016-01-01T00:00:00Z

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publication

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2010-04-01T00:00:00Z

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Copyright 2010 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

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None

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OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

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pointOfContact

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