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Scale sensitivity of the Gill circulation, Part II: off-equatorial case
  • Gilles Bellon,
  • Beatriz Reboredo
Gilles Bellon
University of Auckland

Corresponding Author:gilles.bellon@auckland.ac.nz

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Beatriz Reboredo
University of Auckland
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We investigate the steady dynamical response of the atmosphere on the equatorial β-plane to a steady, localized, mid-tropospheric heating source. Following Part I which investigated the case of an equatorial diabatic heating, we explore the sensitivity of the Gill circulation to the latitudinal location of the heating, together with the sensitivity to its horizontal scale. Again, we focus on characteristics of the response which would be particularly important if the circulation interacted with the hydrologic and energy cycles. In the off-equatorial case, the intensity of the overturning circulation has the same limit as in the equatorial case for small horizontal extent of the diabatic heating, which is also the limit in the non-rotating case and the ƒ-plane case. The decrease in this intensity with increasing horizontal scale of the diabatic heating is slightly faster in the off-equatorial case than in the equatorial case, but slower than in the ƒ-plane case, which shows that the β effect disrupts the rotational motion.
The low-level westerly jet is more intense than in the equatorial case, with larger maximum wind and eastward mass transport that tend to infinity for small horizontal extent of the diabatic heating. While the latitudinal extent of the jet is not very sensitive to the latitude of the diabatic heating, it is not symmetric with respect to the latitude of the diabatic-heating center, unlike in the equatorial case: it extends further equatorward than poleward of the diabatic-heating center. It also extends further eastward than in the equatorial case.
Jan 2022Published in Journal of the Atmospheric Sciences volume 79 issue 1 on pages 19-30. 10.1175/JAS-D-21-0068.1