Projection of climate extremes in the Zhujiang River basin using a regional climate model

Based on the representative concentration pathway (RCP) scenarios, projected changes in climate extremes events in the Zhujiang River basin were investigated using the regional climate model RegCM4.0. Four extreme temperature indices (TXx, TNn, SU30, and TMINmean) and five extreme precipitation indices (Rx1day, Rx5day, SDII, R50mm, and SDII) defined by the Expert Team on Climate Change Detection and Indices (ETCCDI) were used in the investigation. The performance of the model was validated through comparison between observations and simulations for the period 1971-2000. The results show that although RegCM4.0 has certain abilities to reproduce both the spatial distributions of the values of extreme climate indices and their trends in the Zhujiang River basin, there are some large biases in the model results. The model simulates extreme temperatures more accurately than extreme precipitation. Compared to the baseline period 1971-2000, the changes in future (2021-2050 and 2051-2080) climate extremes under the RCP4.5 and RCP8.5 scenarios show very similar patterns, with an increase in extreme temperatures across the entire region and an increase in extreme precipitation in most parts of the region. For the period 2006-2099, a significant warming trend can be expected under both emissions scenarios, especially under the high emissions scenario (RCP8.5). The risk of drought shows statistically significant increasing trends under the RCP8.5 scenario in most parts of the region, especially in the central part of the basin. Meanwhile, more intense rainfall events are expected to occur in most parts of the region, especially in the southern parts of the basin. Furthermore, the increases predicted under the RCP8.5 scenario are more pronounced than those predicted under the RCP4.5 scenario. Overall, our results suggest that the Zhujiang River basin will suffer more natural disasters, such as catastrophic floods, droughts, and heat weaves, in the future.