Projection and uncertainties of extreme precipitation over the Yangtze River valley in the early 21st century

Intensity, frequency and duration of extreme precipitation would increase in the future under a warming climate. This phenomenon will be specifically significant in the Yangtze River valley, where precipitation is sensitive to climate change. Due to uncertainties in models results, the accuracy of extreme precipitation projection is still an open issue. In order to better understand possible changes of extreme precipitation over the middle and lower reaches of Yangtze River, this study evaluates the performance of 19 CMIP5 GCMs from the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) in simulating extreme precipitation and compare the results with observations at 178 stations in Yangtze River valley during 1981-2005. The projection under the RCP4.5 scenario for the early 21st century is then given. The results show that the downscaling models have excellent performance in simulating extreme precipitation in this region; the spatial correlation coefficients between all models and observations are larger than 0.6 except the R90N, while the correlation coefficients of PRCPTOT and R10 with observations are even higher than 0.95. Extreme precipitation tends to increase during the early 21st century, especially over the western part of the Yangtze River valley. The days of extreme precipitation (R90N) would decrease and the R95T and PRCPTOT would increase, which indicates that the amount of extreme precipitation is mainly attributed to contributions of the R95T instead of more days of extreme precipitation. The largest uncertainties occur in southern part of the region while the smallest uncertainties are found in the western part of the region. More attention should be paid to the increase of extreme precipitation in the western part.