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A theory of the MJO horizontal scale

Yang, Da and Ingersoll, Andrew P. (2014) A theory of the MJO horizontal scale. Geophysical Research Letters, 41 (3). pp. 1059-1064. ISSN 0094-8276.

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Here we ask, what controls the horizontal scale of the Madden-Julian Oscillation, i.e., what controls its zonal wave number k? We present a new one-dimensional (1D) β-plane model that successfully simulates the MJO with the same governing mechanism as the 2D shallow water model of Yang and Ingersoll (2013). Convection is parameterized as a short-duration localized mass source that is triggered when the layer thickness falls below a critical value. Radiation is parameterized as a steady uniform mass sink. Both models tend toward a statistically steady state—a state of radiative-convective equilibrium, not just on a global scale but also on the scale of each MJO event. This gives k ~ (S_(c)/c)^(1/2), where S_c is the spatial-temporal frequency of convection events and c is the Kelvin wave speed. We offer this scaling as a prediction of how the MJO would respond to climate change.

Item Type:Article
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Ingersoll, Andrew P.0000-0002-2035-9198
Additional Information:© 2014 American Geophysical Union. Received 31 October 2013; Accepted 27 December 2013; Accepted article online 3 January 2014; Published online 7 February 2014. Da Yang was supported by the Earle C. Anthony Professor of Planetary Science Research Pool and the Division of Geological and Planetary Sciences Davidow Fund of the California Institute of Technology. He is currently supported by the National Science Foundation under grant AST-1109299. We thank these organizations for their support. The Editor thanks two anonymous reviewers for assistance evaluating this manuscript.
Funding AgencyGrant Number
Earle C. Anthony Professor of Planetary Science Research PoolUNSPECIFIED
Caltech Division of Geological and Planetary Sciences Davidow FundUNSPECIFIED
Subject Keywords:Madden-Julian Oscillation; Triggered convection; Gravity waves; Radiative-convective equilibrium; Climate change
Record Number:CaltechAUTHORS:20140501-094446702
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Official Citation:Yang, D., and A. P. Ingersoll (2014), A theory of the MJO horizontal scale, Geophys. Res. Lett., 41, 1059–1064, doi:10.1002/2013GL058542.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45400
Deposited By: Jason Perez
Deposited On:01 May 2014 21:08
Last Modified:14 Sep 2017 22:15

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