"Tropical and extratropical general circulation in an high obliquity planet"
Speaker: Wanying Kang, graduate student in the Tziperman group
Abstract: Planets with high obliquity receive more radiation in the polar regions than in low latitudes, and thus, with a relatively high surface capacity, their meridional temperature gradient tends to be reversed for the entire year as shown in previous studies. To reduce the meridional temperature gradient, a reversed residue circulation comes up into being. Besides this, would such a planet also have a reversed meridional circulation, namely a prevailing Hadley cell subsiding in the deep tropics, and a thermally indirect Ferrell cell descending in the high latitudes? Would the surface wind reverse its sign together with the circulation direction? Exploring the general circulation of such planets also helps us understand the interplay between the Hadley cell and eddy-driven circulation in the Earth’s atmosphere.
I seek answer to these questions by using a 3D dry dynamic model under both eddy-permitting and axisymmetric configurations, aided with a generalized 2D Eady model that includes the beta effect as well as realistic profiles of the vertical wind shear and stratification. Under a reversed meridional temperature gradient scenario, the Hadley cell is much weaker and shallower, due to the easterly momentum drag induced by the mid-latitude eddies. These eddies also change their vertical structures in the reverse case, with amplitude peak near the surface instead of near the tropopause. Such changes can be explained by the most unstable modes in the generalized Eady model.
Lunch will be provided. As always, please plan to bring reusable plates and cutlery to reduce waste.