Abstract/Summary

The characteristics of tropical cyclone (TC) activity over 5 TC basins lying within four Coordinated Regional Downscaling Experiment (CORDEX) domains are examined for present and future climate conditions using a new ensemble of projections completed as part of the CORDEX-CORE initiative with the regional climate model RegCM4. The simulations were conducted on a 25 km horizontal grid spacing using lateral and lower boundary forcing from three CMIP5 global climate models (GCMs) under two Radiative Concentration Pathways (RCP2.6 and RCP8.5). The RegCM4 is capable of capturing most features of the observed TC climatology over the different basins and exhibits a much-improved simulation of TC statistics compared to the driving GCMs. Analysis of the influence of global warming on TC activity indicates significant increases in their frequency over the North Indian Ocean, the Northwest Pacific and Eastern Pacific regions. These changes are consistent with an increase in mid-tropospheric relative humidity. On the other hand, the North Atlantic and Australasia regions show a decrease in TC frequency, mostly associated with an increase in wind shear. We also find a consistent increase in future storm rainfall rates associated with TCs and in the frequency of the most intense TCs over most domains. Our study shows robust and statistically significant responses often, but not always, in line with previous studies, still implying the presence of significant uncertainties. A robust assessment of TC changes requires analyses of ensembles of simulations with high-resolution models capable of representing the response of different TC characteristics to key atmospheric factors.