Meriodional momentum flux and super-rotation in the multi-scale IPESD MJO model

The derivation of the meridional momentum flux arising from a multiscale horizontal velocity field in the intraseasonal, planetary, equatorial synoptic-scale dynamics (IPESD) multiscale models of the equatorial troposphere is presented. It is shown that, because of the balance dynamics on the synoptic scales, the synoptic-scale component of the meridional momentum flux convergence must always vanish at the equator. Plausible Madden-Julian oscillation (MJO) models are presented along with their planetary-scale meridional momentum fluxes. These models are driven by synoptic-scale heating fluctuations that have vertical and meridional tilts. Irrespective of the sign of the synoptic-scale meridional momentum flux (direction of the tilts) in each of the four MJO examples, the zonal and vertical mean meridional momentum flux convergence from the planetary scales always drives westerly winds near the equator: this is the superrotation characteristic of actual MJOs. The concluding discussion demonstrates that equatorial superrotation occurs when the planetary flow due to the vertical upscale momentum flux from synoptic scales reinforces the horizontally convergent flow due to planetary-scale mean heating.

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Author Biello, J.
Majda, A.
Moncrieff, Mitchell W.
Publisher UCAR/NCAR - Library
Publication Date 2007-05-01T00:00:00
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Topic Category geoscientificInformation
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Metadata Date 2025-07-17T17:02:13.806065
Metadata Record Identifier edu.ucar.opensky::articles:6649
Metadata Language eng; USA
Suggested Citation Biello, J., Majda, A., Moncrieff, Mitchell W.. (2007). Meriodional momentum flux and super-rotation in the multi-scale IPESD MJO model. UCAR/NCAR - Library. https://n2t.org/ark:/85065/d790241s. Accessed 28 August 2025.

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