Projecting heavy rainfall events in the middle and lower reach of the Yangtze River valley in the 21st century based on IPCC AR4 simulations

By comparing the modeled climatological states in IPCC AR4 PCMDI simulations with the observed (reanalyzed) climatological states, seven models including gfdl cm2.0, gfdl cm2.1, cgcm, miroc(m), cnrm, echam, and cgcmt47 are selected, due to the better performance over East Asia, from all the fourteen coupled climate system models which have daily precipitation data. The Projection of the heavy rainfall events in the middle and lower reaches of the Yangtze River valley in the 21st century is derived from the experimental runs with the seven models under the three emission scenarios, A1B, A2 and Bl. The results suggest an overall agreement among the models, and averagely the occurrence of the events, the rainfall intensity in a single event, and the interannual variability of events are predicted to be relatively an upward tendency by comparison with that in the latest twenty years of the 20th century (1980-1999). When the different emission scenarios are concerned, the predicted occurrence frequency and intensity under A1B and A2 are higher than that under B1. As for the multiple model ensembles, the occurrence rate of the events is predicted to be increased by 30%, 20%, and l5%, and the intensity in a single event is predicted to be increased by 15%, l0%, and 5% under the emission scenarios A1B, A2, and B1 respectively. Correspondingly, the interannual standard deviations of the event occurrences and the rainfall intensity in a single event are predicted to be increased by 20% and 5% respectively.These indicate there will be not only more occurrence of heavy rainfall events, but also a larger potential increase of extreme heavy rainfall events, as well as more frequent emergence of drought and floods in the future.