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

Axisymmetric Hadley cell theory has traditionally assumed that the tropopause height ( Ht) is uniform and unchanged from its radiative–convective equilibrium (RCE) value by the cells’ emergence. Recent studies suggest that the tropopause temperature ( Tt), not height, is nearly invariant in RCE, which would require appreciable meridional variations in Ht. Here, we derive modified expressions of axisymmetric theory by assuming a fixed Ttand compare the results to their fixed- Htcounterparts. If Ttand the depth-averaged lapse rate are meridionally uniform, then at each latitude Htvaries 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 Ttalters 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 Ttis 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.

 
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Award ID(s):
1912673
NSF-PAR ID:
10140601
Author(s) / Creator(s):
 ;  ;  
Publisher / Repository:
American Meteorological Society
Date Published:
Journal Name:
Journal of the Atmospheric Sciences
Volume:
77
Issue:
4
ISSN:
0022-4928
Page Range / eLocation ID:
p. 1279-1294
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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