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Solsticial Hadley Cell ascending edge theory from supercriticality

Hill, Spencer A. and Bordoni, Simona and Mitchell, Jonathan L. (2021) Solsticial Hadley Cell ascending edge theory from supercriticality. Journal of the Atmospheric Sciences, 78 (6). pp. 1999-2011. ISSN 0022-4928. doi:10.1175/jas-d-20-0341.1.

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How far the Hadley circulation’s ascending branch extends into the summer hemisphere is a fundamental but incompletely understood characteristic of Earth’s climate. Here, we present a predictive, analytical theory for this ascending edge latitude based on the extent of supercritical forcing. Supercriticality sets the minimum extent of a large-scale circulation based on the angular momentum and absolute vorticity distributions of the hypothetical state were the circulation absent. We explicitly simulate this latitude-by-latitude radiative–convective equilibrium (RCE) state. Its depth-averaged temperature profile is suitably captured by a simple analytical approximation that increases linearly with sinφ, where φ is latitude, from the winter to the summer pole. This, in turn, yields a one-third power-law scaling of the supercritical forcing extent with the thermal Rossby number. In moist and dry idealized GCM simulations under solsticial forcing performed with a wide range of planetary rotation rates, the ascending edge latitudes largely behave according to this scaling.

Item Type:Article
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URLURL TypeDescription
Hill, Spencer A.0000-0001-8672-0671
Bordoni, Simona0000-0003-4771-3350
Additional Information:© 2021 American Meteorological Society. Manuscript received 11 November 2020, in final form 22 March 2021. Published-online: 10 Jun 2021. We are very grateful to Sean Faulk and Martin Singh for sharing the data from their simulations and for many valuable discussions. S.A.H. acknowledges financial support from NSF Award 1624740 and from the Monsoon Mission, Earth System Science Organization, Ministry of Earth Sciences, Government of India. J.L.M. acknowledges funding from the Climate and Large-scale Dynamics program of the NSF, Award 1912673. We thank Martin Singh and two anonymous reviewers for helpful comments.
Funding AgencyGrant Number
Ministry of Earth Sciences (India)UNSPECIFIED
Subject Keywords:Hadley circulation; Troposphere; General circulation models
Issue or Number:6
Record Number:CaltechAUTHORS:20210716-230219944
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Official Citation:Hill, S. A., Bordoni, S., & Mitchell, J. L. (2021). Solsticial Hadley Cell Ascending Edge Theory from Supercriticality, Journal of the Atmospheric Sciences, 78(6), 1999-2011; DOI: 10.1175/jas-d-20-0341.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109907
Deposited By: Tony Diaz
Deposited On:16 Jul 2021 23:08
Last Modified:16 Jul 2021 23:08

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