Abstract:

The evaluation on simulated runoff over China from the five regional climate model ensemble simulations was conducted. Based on these simulations, future changes in runoff under the high emission scenario RCP8.5 were also projected. The results show that the ensemble mean simulations can well capture the observed features of runoff. The simulation on spatial pattern of annual runoff performs well, while certain biases exist, especially the positive biases over the middle reach of Yellow River basin, the Haihe River basin, and the Song-Liao River basin. The simulations on the monthly contributions perform relatively poor over Southeastern, Southwestern, and Northwestern rivers basins among nine basins of China. From now to the end of 21st century, national mean annual runoff will mostly increase, with the magnitude of less than 5%. There are spatial differences in annual runoff changes, with roughly “increase in north, decrease in south”. However, the climatic pattern of runoff ranging from wet south to dry north will not change. The area-averaged trends are significant positive over the Yellow River, Southwestern and Northwestern rivers basins, significant negative over the Huaihe River, Yangtze River, and Southeastern rivers basins, and there are no significant trends over the Haihe River, Song-Liao River and Zhujiang River basins. At the end of 21st century, the changes are mostly within ±30% across China, and the agreements on change sign are high. At the end of 21st century, the overall characteristics of monthly contributions over each basin will change little, with the peak months mostly unchanged. The changes in monthly contributions will be within ±2%, and there are large differences among nine basins in increases or decreases at certain month or season.

Key words: Regional climate model, Runoff, Evaluation, Projection