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Axisymmetric Hadley Cell Theory with a Fixed Tropopause Temperature Rather than Height

Hill, Spencer A. and Bordoni, Simona and Mitchell, Jonathan L. (2020) Axisymmetric Hadley Cell Theory with a Fixed Tropopause Temperature Rather than Height. Journal of the Atmospheric Sciences, 77 (4). pp. 1279-1294. ISSN 0022-4928. https://resolver.caltech.edu/CaltechAUTHORS:20200514-130939068

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Abstract

Axisymmetric Hadley cell theory has traditionally assumed that the tropopause height (H_t) is uniform and unchanged from its radiative–convective equilibrium (RCE) value by the cells’ emergence. Recent studies suggest that the tropopause temperature (T_t), not height, is nearly invariant in RCE, which would require appreciable meridional variations in H_t. Here, we derive modified expressions of axisymmetric theory by assuming a fixed T_t and compare the results to their fixed-H_t counterparts. If T_t and the depth-averaged lapse rate are meridionally uniform, then at each latitude H_t varies linearly with the local surface temperature, altering the diagnosed gradient-balanced zonal wind at the tropopause appreciably (up to tens of meters per second) but the minimal Hadley cell extent predicted by Hide’s theorem only weakly (≲1°) under standard annual-mean and solsticial forcings. A uniform T_t alters the thermal field required to generate an angular-momentum-conserving Hadley circulation, but these changes and the resulting changes to the equal-area model solutions for the cell edges again are modest (<10%). In numerical simulations of latitude-by-latitude RCE under annual-mean forcing using a single-column model, assuming a uniform T_t is reasonably accurate up to the midlatitudes, and the Hide’s theorem metrics are again qualitatively insensitive to the tropopause definition. However imperfectly axisymmetric theory portrays the Hadley cells in Earth’s macroturbulent atmosphere, evidently its treatment of the tropopause is not an important error source.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1175/jas-d-19-0169.1DOIArticle
ORCID:
AuthorORCID
Hill, Spencer A.0000-0001-8672-0671
Bordoni, Simona0000-0003-4771-3350
Additional Information:© 2020 American Meteorological Society. Manuscript received 24 June 2019, in final form 7 February 2020. Published online: 23 March 2020. We thank two anonymous reviewers for catching several important mistakes in an earlier draft and for other helpful comments; addressing them greatly improved the manuscript. We thank Brian Rose for developing climlab and timely guidance in using it. S.A.H. was initially supported by NSF Atmospheric and Geospace Sciences Postdoctoral Research Fellowship (Award 1624740), and subsequently by the Caltech Foster and Coco Stanback Postdoctoral Fellowship. S.B. was supported by NSF Award AGS-1462544.
Funders:
Funding AgencyGrant Number
NSFAGS-1624740
Foster and Coco Stanback Postdoctoral FellowshipUNSPECIFIED
NSFAGS-1462544
Issue or Number:4
Record Number:CaltechAUTHORS:20200514-130939068
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200514-130939068
Official Citation:Hill, S.A., S. Bordoni, and J.L. Mitchell, 2020: Axisymmetric Hadley Cell Theory with a Fixed Tropopause Temperature Rather than Height. J. Atmos. Sci., 77, 1279–1294, https://doi.org/10.1175/JAS-D-19-0169.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103201
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:14 May 2020 21:32
Last Modified:14 May 2020 21:32

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