本文根据政府间气候变化委员会 (IPCC) 第四次评估报告 (AR4) (简称IPCC-AR4) 中22个耦合模式对20世纪气候模拟 (20C3M) 结果中20世纪晚期亚洲夏季风降水的模拟所显示出各模式模拟能力的较大空间差异, 提出了一种滑动窗区空间相关系数来量化表征这种空间差异特征, 结果表明, 该系数明显优于传统空间相关系数, 其空间分布能够较为细致地描述各模式对较小区域模拟性能的空间差异特征。在此基础上, 本文提出以这种滑动窗区空间相关系数作为各模式的权重系数进行加权集合平均, 并称之为滑动窗区空间相关系数加权集合方法。利用该方法对IPCC-AR4 22个耦合模式所模拟的20世纪晚期亚洲夏季风降水进行加权集合平均, 并将其结果与传统空间相关系数加权集合平均以及等权重多模式集合平均结果进行比较, 表明了利用本文所提出的加权集合方法对20世纪晚期亚洲夏季风降水的集合模拟结果明显优于简单的等权重多模式集合平均结果以及传统空间相关系数加权集合平均结果。鉴于此原因, 本文利用此方法对在A1B (各种能源均衡发展) 排放情景下IPCC-AR4中22个耦合模式所模拟的21世纪各时期亚洲夏季风降水演变趋势进行集合预测。其结果表明: 在A1B排放情景下, 从21世纪中期 (2045～2065年) 开始南亚夏季风降水将比20世纪晚期明显增强; 而东亚夏季风降水相对于20世纪晚期的变化呈现出从南到北经向三极子型异常分布特征, 即华南和华北地区夏季风降水增多, 而长江流域夏季风降水相对于20世纪晚期没有太大变化。并且, 结果还表明亚洲夏季风降水异常这种变化趋势可以延续到21世纪晚期。
A weighting ensemble method (WEM) by pattern correlation coefficients (PCC) in sliding windows (SWPCC) (WEMSWPCC) is proposed according to distinct pattern differences among simulation performances of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) (IPCC-AR4) 22 coupled models for Asian summer monsoon precipitation in the late 20th century under scenario 20C3M (20th century climate coupled models simulations). By comparing the distributions of SWPCC and the distributions of simulations of 22 models, it is shown that the SWPCC can quantitatively reflect the pattern differences in each regional window among these models. Furthermore, the comparisons among the ensemble simulations with various ensemble methods and the observed result, it is also shown that the ensemble simulation of Asian summer monsoon precipitation in the late 20th century with the WEMSWPCC proposed in this paper is better than both that with the simple multi-model ensemble method (SMMEM) and that with the traditional pattern correlation coefficients (TPCC) weighting ensemble method (WEMTPCC). For this reason, the WEMSWPCC ensemble method is applied to the ensemble predictions of the evolution trend of Asian summer monsoon precipitations for various periods of the 21st century under the A1B emission scenario by IPCC-AR4 22 coupled models. The results show that under the A1B emission scenario, the South Asian summer monsoon precipitation in the middle period of the 21st century (2045－2065) will be significantly stronger than that in the late period of the 20th century, while the East Asian summer monsoon precipitation anomalies will exhibit a meridian tripole pattern distribution from the south to the north in the middle period of the 21st century as compared with those in the late period of the 20th century. That is, the summer monsoon precipitation in North China and South China will obviously increase in comparison with that in the late period of the 20th century, but it has not obvious change in the Yangtze River valley, compared with that in the late period of the 20th century. Moreover, the results also show that this evolution trend of Asian summer monsoon precipitation may continue to the late period of the 21st century.