CMIP5模式对我国西南地区干湿季降水的模拟和预估

利用降水观测资料, 评估了参加国际耦合模式比较计划第五阶段(CMIP5)的34个全球模式对1986～2005年我国西南地区干湿季降水的模拟能力。结果表明, 34个CMIP5模式中分别有30和25个模式模拟的干季和湿季降水偏多。34个模式对我国西南地区干湿季降水的模拟能力差异较大, 大约半数模式的模拟值与观测值的空间相关系数通过了99%的信度检验, 且标准差之比小于2。利用两个技巧评分标准, 分别挑选出了对干湿季降水模拟最优的9个模式。最优模式集合平均结果要优于34个模式的集合平均, 更要优于大多数单个模式。进一步利用最优的9个模式的集合平均对RCP4.5和RCP8.5两种典型浓度路径下我国西南地区干湿季降水的变化进行了预估。相对于1986～2005年气候平均态, 在21世纪初期(2016～2035年), 我国西南地区干季降水变化表现为川西高原降水增多, 而四川盆地及攀西地区、重庆、贵州和云南的大部分地区降水减少;湿季降水变化表现为川西高原、贵州和广西大部分地区降水增多, 而四川盆地及攀西地区和云南降水减少。在21世纪中期(2046～2065年)和末期(2080～2099年), 西南地区干湿季降水普遍增多。在RCP8.5情景下, 降水的变化幅度要强于RCP4.5情景。

Evaluation and Projection of Dry- and Wet-Season Precipitation in Southwestern China Using CMIP5 Models

In this study, we use observational datasets to evaluate the performance of 34 models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) in simulating dry- and wet-season precipitation over southwestern China during 1986-2005. Of the 34 CMIP5 models, 30 and 25 models overestimate dry- and wet-season precipitation, respectively. The ability of 34 models to simulate dry- and wet-season precipitation is found to differ significantly. Moreover, approximately half of the models show that spatial correlation coefficients with the observations are significant at the 99% confidence level and the ratios of the simulated standard deviations to the observed values are less than 2. On the basis of the two skill scores, we select the nine best models for simulating dry- and wet-season precipitation. The 9-model ensemble mean performs better than the ensemble mean of all 34 models and most of the individual models. Therefore, we further use nine-model ensemble mean to project dry- and wet-season precipitation changes under Representative Concentration Pathways RCP4.5 and RCP8.5 scenarios over southwestern China. Compared with the climatology of 1986-2005, the dry-season mean precipitation is projected to increase in the west Sichuan plateau and decrease in the Sichuan Basin, the Panxi region, Chongqing, Guizhou, and the most of Yunnan province during 2016-2035. During the same period, the wet-season mean precipitation is projected to increase in west Sichuan plateau and most of Guizhou and Guangxi and decrease over Sichuan basin, the Panxi region, and Yunnan Province. Both dry- and wet-season precipitation is projected to increase throughout nearly the entire southwestern China region under the two scenarios in the middle and late 21st century. Under the RCP8.5 scenario, the changes in magnitude of dry- and wet-season precipitation are stronger than those under the RCP4.5 scenario.