Future projection of extreme precipitation within CORDEX East Asia phase II: multi-model ensemble

Driven by the outputs of four global climate models from Coupled Model Intercomparison Project Phase 5, a long-term downscaling and projection under the RCP8.5 scenario is conducted within the Coordinated Regional Downscaling Experiment East Asia phase II framework with Weather Research and Forecasting Model (WRF) and Regional Climate Model version 4 (RegCM4). All the single simulations and the ensembles well reproduce the spatial pattern of the precipitation amount over East Asia with the spatial correlations (SCORs) larger than 0.58, although bias exists in some areas. The models also reasonably present the spatial patterns of the extreme precipitation indices except the Rx5day (annual maximum consecutive 5-day precipitation) and the consecutive dry days (CDD), with the SCORs ranging between 0.43 and 0.71. In general, WRF outperforms RegCM4 in producing the spatial patterns of most extreme precipitation indices and RegCM4 generates lower root mean square errors. In the future, the precipitation amount would significantly increase in northeastern China and northwestern China and over the Tibetan Plateau, which is mainly due to the increase of precipitation intensity in WRF and frequency in RegCM4. The extreme frequency and intensity indices are projected to significantly increase over the Tibetan Plateau and some areas of northwestern China. In addition, the consecutive wet days will get significantly longer in the above regions, where the consecutive dry days will shorten, indicating more consecutive precipitation events in the future. The change in the probability distribution of the extreme indices reveals that stronger and longer-duration extreme precipitation events would get more frequent in the future. The increase of low-level specific humidity can partly explain the increase of precipitation.