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A Theory for the Hadley Cell Descending and Ascending Edges throughout the Annual Cycle

Hill, Spencer A. and Bordoni, Simona and Mitchell, Jonathan L. (2022) A Theory for the Hadley Cell Descending and Ascending Edges throughout the Annual Cycle. Journal of the Atmospheric Sciences, 79 (10). pp. 2515-2528. ISSN 0022-4928. doi:10.1175/jas-d-21-0328.1.

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We present a theory for the latitudinal extents of both Hadley cells throughout the annual cycle by combining our recent scaling for the ascending edge latitude based on low-latitude supercriticality with the theory for the poleward, descending edge latitudes of Kang and Lu based on baroclinic instability and a uniform Rossby number (Ro) within each cell’s upper branch. The resulting expressions for all three Hadley cell edges are predictive except for diagnosed values of Ro and two proportionality constants. Thermal inertia—which damps and lags the ascent latitude relative to the insolation—is accounted for semianalytically through the Mitchell et al. model of an “effective” seasonal forcing cycle. Our theory, given empirically an additional ∼1-month lag for the descending edge, captures the climatological annual cycle of the ascending and descending edges in an Earthlike simulation in an idealized aquaplanet general circulation model (GCM). In simulations in this and two other idealized GCMs with varied planetary rotation rate (Ω), the winter, descending edge of the solsticial, cross-equatorial Hadley cell scales approximately as Ω^(−1/2) and the summer, ascending edge as Ω^(−2/3), both in accordance with our theory. Possible future refinements and tests of the theory are discussed.

Item Type:Article
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URLURL TypeDescription
Hill, Spencer A.0000-0001-8672-0671
Bordoni, Simona0000-0003-4771-3350
Additional Information:We are grateful to Sean Faulk and Martin Singh for sharing the data from their simulations and for many valuable discussions. We thank Ilai Guendelman and three anonymous reviewers for helpful comments. 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.
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Ministry of Earth Sciences (India)UNSPECIFIED
Issue or Number:10
Record Number:CaltechAUTHORS:20230103-818063100.47
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:118639
Deposited By: Research Services Depository
Deposited On:07 Feb 2023 20:10
Last Modified:07 Feb 2023 20:10

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