Towards Development of a Climate Theory of Tropical Cyclone Genesis

While significant advances have been made in the quantitative links between climate and tropical cyclone (TC) intensity, the links between climate and TC formation are much less well understood. To contribute to the development of a quantitative climate theory of TC genesis, the present study investigates how interannual variations in tropical climate conditions influence the year-to-year variation of TC formation rate, using the global TC best-track data (IBTrACS) and ERA-Interim reanalyses for the period of 1979-2014. In particular, we here investigate the applicability of the weak temperature gradient approximation to the changes in TC formation rates, as modulated by maximum potential intensity. These relationships will also be used to analyze a selection of high resolution climate model simulations from U.S. Climate Variability and Predictability Research Program (CLIVAR) Hurricane Working Group (HWG) to provide explanations for why TC behaviour might change in future climate scenarios. Further analyses of global TC formation are made based on a high resolution (~40 km) version of the Australian Community Climate and Earth System Simulator (ACCESS) model. The results discussed here could further contribute to the improvement of seasonal and climate change prediction of TCs.