Tropical Precipitation and Cross-Equatorial Heat Transport in Response to Localized Heating: Basin and Hemisphere Dependence

Abstract

A heat source is applied to different surface locations in a fully coupled climate model to study the cross-equatorial energy transport and tropical precipitation responses. Remarkably different tropical precipitation responses are seen, varying from a large shift toward, to a small shift away from, the heated hemisphere. These differences are dominated by changes in top-of-atmosphere radiation, with some contribution from changes in ocean cross-equatorial heat flux. The atmospheric fraction of the total cross-equatorial heat flux is consistently larger for Northern Hemisphere (NH) heating relative to Southern Hemisphere heating. This results in a larger tropical rainfall shift in response to NH heating. Positive shortwave radiative feedbacks, associated with a burn-off of low clouds in the North Pacific, also amplify the tropical rainfall response to NH heating. The Pacific Ocean dominates the ocean response to Southern Hemisphere heating, while the Atlantic Ocean dominates the ocean response to NH heating.