Tropical cyclones in a regional climate change projection with RegCM4 over the CORDEX Central America domain

The characteristics of tropical cyclones (TCs) over the Central America Coordinated Regional Downscaling Experiment (CORDEX) domain are examined for present and future climate conditions using the regional climate model RegCM4. RegCM4 is first tested in a 22 year (1982-2003) simulation with boundary forcing from the ERA-Interim reanalysis, showing a generally good performance in reproducing the observed TC climatology and over the Atlantic in reproducing the interannual variations of TC counts. Four scenario simulations (1970-2100) are generated using two model configurations and two driving global models (MPI and HadGEM). The simulations employing the Grell convection scheme produce too few TCs, while those using the Emanuel convection scheme reproduce the observed climatology, especially when driven by the MPI global model. The simulation of TCs is thus sensitive to both the model convection scheme and the forcing GCM. Comparison of future and present day TC statistics indicates that the frequency of future TCs decreases over the tropical Atlantic and the East Pacific coastal areas while it increases over the western areas of the East Pacific and the northern areas of the Atlantic. We also find an increase in the frequency of intense TCs and long lasting TCs, along with a northward shift of TC tracks over the Atlantic. Conclusions on the changes in TC activity are not found to be sensitive to the inclusion of SST thresholds in the detection procedure. These findings provide encouraging indications for the use of the CORDEX framework in the study of TCs and are suggestive of important effects of global warming on the characteristics of TCs in the tropical Atlantic and Pacific basins.