气候变化下淮河流域极端洪水情景预估

Prediction of extreme floods in Huaihe River basin under climate change

利用IPCC第4次评估公开发布的22个全球气候模式在A1B、A2和B1三种典型排放情景下的未来气温和降水预测结果,结合新安江月分布式水文模型,在对模型验证效果良好的基础上,参照集合预报方法,对未来90年(2010～2099年)气候变化下淮河流域的极端洪水进行预估。研究结果表明,从出现概率来看,淮河流域未来可能发生极端洪水年份的密集程度从大到小依次为A2情景、A1B情景、B1情景。A1B情景下,21世纪下半叶出现极端洪水的可能性增大,A2情景在2035～2065年以及2085年以后是极端洪水发生较为集中的时期。B1情景在21世纪70年代左右发生极端洪水的可能性较大。综合各种极端事件的定义方法,将极端洪水划定3个洪水量级。A2情景预估极端洪水的平均洪量在3种情景中最大,B1情景最小。3种情景未来一级极端洪水发生比例都比历史上偏大,A2情景下增加最多。二级极端洪水都较历史略有减少,三级极端洪水减少最显著。3种情景下各个量级极端洪水所占比例各不相同,A1B和A2情景二级以上极端洪水出现比例较大,B1情景下极端洪水量级多为三级,超1954年的一级极端洪水所占比例较小。

Predictions of extreme floods from 2010-2099 are made for the Huaihe River Basin using the projected future temperature and precipitation from 22 global climate models under A1B,A2 and B1 emission scenarios in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change（IPCC AR4） and the Xin＇anjiang monthly distributed hydrological model.The model is calibrated and validated with the satisfied results.The ensemble method is applied in the model prediction.The result shows that the A2 scenario would most likely result in a highest number of extreme flood events,and then followed by the A1B scenario and the B1 scenario,respectively.Under A1B,there would be an increased possibility of extreme flooding in the latter half of the 21st century;while for the A2 scenario,the extreme floods could be concentrated on the period 2035-2065 as well as after 2085.Under B1,the frequent extreme floods would most likely occur around 2070s.By integrating the diverse definitions of extreme events,we classify the extreme events into three groups based on the flood magnitudes.In the first magnitude group,the extreme flood events predicted under the A2 scenario would be the most with the largest average flood volume;while those under B1 would be the least with the minimum value of flood magnitude in the third group.There could be an increased occurrence of the extreme flood events in the first magnitude group among all three scenarios.The highest increase might be found under the A2 scenario and followed by A1B and B1.The proportion of extreme flood events in each of the three magnitude groups would also vary under different scenarios.The extreme flood events of the second magnitude group could be more frequently encountered under A1B and A2;while B1 could result in more third group extreme flooding.Nevertheless,there would only a small proportion of extreme flood events with the flood magnitude exceeding the great flood of 1954 in the first magnitude group.