open access

https://hdl.handle.net/2115/49935

Moist Hadley Circulation: Possible Role of Wave-Convection Coupling in Aquaplanet Experiments

英語

Hadley circulation

2012-03

American Meteorological Society

Journal of the Atmospheric Sciences

69(3)

891-907

Aquaplanet simulations for a given sea surface temperature (SST) are conducted to elucidate possible roles of transient variability in the Hadley circulation and the intertropical convergence zone (ITCZ). Their roles are best illustrated with globally uniform SSTs. For such SSTs, an ITCZ and a Hadley circulation that are nearly equatorially symmetric emerge spontaneously. Their strength varies over a wide range from being faint to climatologically significant depending on a tunable parameter of the model's cumulus parameterization. In some cases asymmetric Hadley circulations formed along with long-lived tropical cyclones. The tunable parameter affects the transient variability of tropical precipitation. In the runs in which well-defined near-symmetric ITCZs formed, tropical precipitation exhibited clear signatures of convectively coupled equatorial waves. The waves can explain the concentration of precipitation to the equatorial region, which induces the Hadley circulation. Also, the meridional structures of simulated ITCZs are consistent with the distribution of convergence/divergence associated with dominant equatorial wave modes. Even when the pole-equator temperature gradient is introduced, the dependence of the strength of the circulation to transient disturbances remains. Therefore, transient variability may have a broader impact on tropical climate and its numerical modeling than has been thought. The reason that a wide variety of circulation is possible when the SST gradient is weak is because the distribution of latent heating can be interactively adjusted while a circulation is formed. Angular momentum budget does not provide an effective thermodynamic constraint, since baroclinic instability redistributes the angular momentum.

学術雑誌論文

Version of Record

© Copyright 2012 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 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or copyright@ametsoc.org.

0022-4928