The Role of Tropical Cyclones in the Global Energy Budget

The total atmospheric radiation budget of the atmosphere leads to a net cooling of tropical regions by 1-2^oC per day, cooling that is balanced locally by mass subsidence and compressional heating. We first demonstrate that potential energy generation in moist vertical motion in tropical cyclones is sufficient to balance around 40% of this cooling. But this leaves the question of how localised, transient tropical cyclones can contribute to the energy balance at locations remote in time and space. We utilise a comprehensive trajectory analysis of reanalysis data to show how this is accomplished by air flowing out of tropical cyclones in the upper levels to spread throughout the tropical clear regions. Because of the long time frames involved in such mass transport, the subsidence and warming to balance the energy budget may occur weeks to months after the cyclone has disappeared.

Discussion will be included on the implications of these findings for the observed annual constancy of global tropical cyclone frequency and for concepts of convective-radiative equilibrium.