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Convective Generation of Equatorial Superrotation in Planetary Atmospheres

Liu, Junjun and Schneider, Tapio (2011) Convective Generation of Equatorial Superrotation in Planetary Atmospheres. Journal of the Atmospheric Sciences, 68 (11). pp. 2742-2756. ISSN 0022-4928.

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In rapidly rotating planetary atmospheres that are heated from below, equatorial superrotation can occur through convective generation of equatorial Rossby waves. If the heating from below is sufficiently strong that convection penetrates into the upper troposphere, then the convection generates equatorial Rossby waves, which can induce the equatorward angular momentum transport necessary for superrotation. This paper investigates the conditions under which the convective generation of equatorial Rossby waves and their angular momentum transport lead to superrotation. It also addresses how the strength and width of superrotating equatorial jets are controlled. In simulations with an idealized general circulation model (GCM), the relative roles of baroclinicity, heating from below, and bottom drag are explored systematically. Equatorial superrotation generally occurs when the heating from below is sufficiently strong. However, the threshold heating at which the transition to superrotation occurs increases as the baroclinicity or the bottom drag increases. The greater the baroclinicity is, the stronger the angular momentum transport out of low latitudes by baroclinic eddies of extratropical origin. This competes with the angular momentum transport toward the equator by convectively generated Rossby waves and thus can inhibit a transition to superrotation. Equatorial bottom drag damps both the mean zonal flow and convectively generated Rossby waves, weakening the equatorward angular momentum transport as the drag increases; this can also inhibit a transition to superrotation. The strength of superrotating equatorial jets scales approximately with the square of their width. When they are sufficiently strong, their width, in turn, scales with the equatorial Rossby radius and thus depends on the thermal stratification of the equatorial atmosphere. The results have broad implications for planetary atmospheres, particularly for how superrotation can be generated in giant planet atmospheres and in terrestrial atmospheres in warm climates.

Item Type:Article
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URLURL TypeDescription
Schneider, Tapio0000-0001-5687-2287
Additional Information:© 2011 American Meteorological Society. Manuscript received 7 December 2010, in final form 6 June 2011. This work was supported by a David and Lucile Packard Fellowship and by the NASA Outer Planets Research Program (Grant NNX10AQ05G). The GCM is based on the Flexible Modeling System of the Geophysical Fluid Dynamics Laboratory. The simulations were performed on Caltechs Division of Geological and Planetary Sciences Dell cluster.
Funding AgencyGrant Number
David and Lucile Packard FellowshipUNSPECIFIED
NASA Outer Planets Research ProgramNNX10AQ05G
Subject Keywords:Convection, Planetary atmospheres, Planetary waves
Issue or Number:11
Record Number:CaltechAUTHORS:20111219-092158853
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Official Citation:Liu, Junjun, Tapio Schneider, 2011: Convective Generation of Equatorial Superrotation in Planetary Atmospheres. J. Atmos. Sci., 68, 2742–2756. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28510
Deposited By: Tony Diaz
Deposited On:19 Dec 2011 21:55
Last Modified:03 Oct 2019 03:33

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