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 depthaveraged temperature profile is suitably captured by a simple analytical approximation that increases linearly with sinu, where u 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.

Solsticial hadley cell ascending edge theory from supercriticality / Hill, S. A.; Bordoni, S.; Mitchell, J. L.. - In: JOURNAL OF THE ATMOSPHERIC SCIENCES. - ISSN 0022-4928. - 78:6(2021), pp. 1999-2011. [10.1175/JAS-D-20-0341.1]

Solsticial hadley cell ascending edge theory from supercriticality

Bordoni S.;
2021

Abstract

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 depthaveraged temperature profile is suitably captured by a simple analytical approximation that increases linearly with sinu, where u 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.
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Hill, S. A.; Bordoni, S.; Mitchell, J. L.
Solsticial hadley cell ascending edge theory from supercriticality / Hill, S. A.; Bordoni, S.; Mitchell, J. L.. - In: JOURNAL OF THE ATMOSPHERIC SCIENCES. - ISSN 0022-4928. - 78:6(2021), pp. 1999-2011. [10.1175/JAS-D-20-0341.1]
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11572/333200
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