CMIP3模式对未来50a欧亚大陆雪水当量的预估

Snow Water Equivalent over Eurasia in Next 50 Years Projected by CMIP3 Models

为研究预估未来50 a欧亚大陆雪水当量,基于遥感数据,用误差百分率、空间相关和误差标准差等统计方法,评估了14个CMIP3模式在20C3M的雪水当量产品,诊断各模式对欧亚大陆雪水当量的模拟能力,在此基础上对模拟效果较好的10个模式产品进行多模式集合,分析了A2和B1情景下2002-2060年欧亚大陆雪水当量的变化.结果表明:欧亚大陆整体的雪水当量在未来50 a呈现一致的减少趋势;空间上,除了欧亚大陆东北部存在显著正趋势外,其余地区均为显著负趋势.季节上,雪水当量在夏季减少的比率最大,但量值上减少最大的却不是在积雪最多的冬季,而是在春季,这是因为春季雪水当量值的减少趋势普遍比冬季大,但增加却普遍比冬季小.未来50 a欧亚大陆冬、春季雪水当量呈现东增西减,且青藏高原明显减少的特征,这将有利于我国东部夏季雨带的北抬.雪水当量在A2情景下的减小范围和速率都要大于B1情景,表明较高的温室气体排放将从时间和空间上加快雪水当量的减少,不利于积雪的维持,控制温室气体排放对于未来欧亚大陆积雪的生存至关重要.

Based on the remote sensing snow water equivalent （SWE） data, the simulated SWE in 20C3M experiments from 14 models attending the third phase of the Coupled Models for Inter-com- parison Project was first evaluated by computing difference percentage, spatial correlation coefficient, and standard deviation of bias during 1979-- 2000. Then, the diagnosed 10 models with higher ability in simulating Eurasian SWE were aggregated by arithmetic mean to project the changes of Eurasian SWE in 2002--2060. The results show that SWE will decrease significantly for Eurasia as a whole in the next 50 years. Spatially, significant decreasing trends dominate except for the significant increasing in the northeastern Eurasia. Seasonally, the decreasing proportion is greatest in summer indicating snow cover in warmer season is more sensitive to climate warming, but the abso-lute decreasing trends are not greatest in winter, hut in spring. This is caused by the greater magnitude of negative trends, but smaller positive trends in spring than in winter. The changing characteris- tics of increasing in eastern and decreasing in western Eurasia and decreasing over the Tibetan Plat- eau favor the viewpoint that there will be more rainfall in the North China and less in the middle and lower reaches of the Yangtze River in summer. Additionally, the decreasing rate and scope with significant decreasing trends under SRES A2 are greater than those under SRES B1, indicating that the emission of green house gases （GHG） will speed up the decreasing rate of snow cover both temporally and spatially. It is crucial to control the discharge of GHG emissions for mitigating the disappearance of snow cover over Eruasia.