General circulation under reversed merdional temperature gradient

Abstract:

General circulation under reversed merdional temperature gradient

Planets with high obliquity may widely exist in the universe in absence of a large moon. Heated more over the polar regions than equator, high obliquity planets are expected to have a reversed meridonal temperature gradient.

Using a model hierarchy, from a 1D Eady-like model to a 3D dry dynamic model and then to a full GCM, we attempt to draw a picture for the high obliquity climate and answer questions such as 1) whether the general circulation would simply reverse its direction with the meridional temperature gradient, 2) whether obliquity would affect the surface energy balance and thereby the global surface temperature, 3) whether obliquity would affect the water transport into the stratosphere, which can potentially be detected. Understanding the atmospheric dynamics under such an exotic configuration allows us to examine and generalize our understandings based on Earth. We realized that atmospheric motions, even in the tropics, do not necessarily rise (or sink) in warm (or cold) regions/latitude bands. The top-amplified baroclinic wave structure is not only a result out of the vertical density decay. Also, injection of atmosphere into the stratosphere cannot only occur in the tropics, driven by Brewer-Dobson circulation.

Reference:

Kang. W. 2019, Regime transition between eddy-driven and moist-driven circulation on High Obliquity Planets, Astrophysical Journal, 884:1

Kang. W. 2019, Wetter Stratospheres on High Obliquity Planets, Astrophysical Journal Letter, 877:1

Kang, W. 2019, Mechanisms leading to a warmer climate on high obliquity planets, Astrophysical Journal Letter, 876:1

Kang, W., M. Cai and E. Tziperman, 2019, Tropical and Extratropical General Circulation with a Meridional Reversed Temperature Gradient as Expected in a High Obliquity Planet, Icarus