Why are there more tropical cyclones in the northern hemisphere?

Abstract:

Tropical cyclones only develop over oceans, and while oceans cover a somewhat larger fractional area in the southern hemisphere, only roughly 30% of the world’s tropical cyclone occur there. In this talk I will explore reasons for this, hoping to shed some light on the more general question of climate control of tropical cyclone activity. The talk will focus on two major but not mutually exclusive hypotheses: The asymmetry in poleward ocean heat transport between the two hemispheres, and the indirect effect on tropical cyclone potential intensity of the stronger seasonal cycle over land in the northern hemisphere. I will show that the latter produces high seasonal peaks in potential intensity and tropical cyclone genesis potential over adjacent oceans than would occur without nearby land masses (where “nearby” means within a deformation radius).