CMIP6模式对欧亚大陆冬季雪水当量的模拟能力评估及未来预估

Evaluation and Projection of the Eurasian Winter Snow Water Equivalent Based on CMIP6 Models

基于第六次耦合模式比较计划(CMIP6)的模式模拟数据和欧洲宇航局GlobSnow卫星遥感雪水当量(Snow Water Equivalent,SWE)资料,评估了CMIP6耦合模式对1981~2014年欧亚大陆冬季SWE的模拟能力,并应用多模式集合平均结果预估了21世纪欧亚大陆SWE的变化情况。结果表明,CMIP6耦合模式对冬季欧亚大陆中高纬度SWE空间分布具有较好的再现能力,能模拟出欧亚大陆中高纬度SWE的主要分布特征;耦合模式对SWE变化趋势及经验正交函数主要模态特征的模拟能力存在较大差异,但多模式集合能提高模式对SWE变化趋势和主要时空变化特征的模拟能力;此外,多模式集合结果对欧亚大陆冬季SWE与降水、气温的关系也有较好的再现能力。预估结果表明,21世纪欧亚大陆东北大部分地区的SWE均要高于基准期(1995~2014年),而90°E以西的欧洲大陆SWE基本上呈现减少的特征;21世纪早期,4种不同排放情景下积雪变化的差异不大,但21世纪后期积雪变化的幅度差异较大,而且排放越高积雪变化的幅度越大,模式不确定性也越大;进一步的分析表明,欧亚大陆冬季未来积雪变化特征的空间分布与全球变化背景下局地气温、降水的变化密切相关,高温高湿的条件有利于欧亚大陆东北部积雪的增多。

Historical simulation outputs of climate models from the Coupled Model Intercomparison Program Phase 6(CMIP6),in addition to the GlobSnow monthly Snow Water Equivalent(SWE)products,were used to assess the model performance in the simulation of the Eurasian winter SWE.Most models can reproduce the basic features of the climatological Eurasian winter SWE relatively well.There are significant differences in different models regarding the trend of SWE,but the MultiModel Ensemble(MME)can produce more realistic simulation results.The spatial and temporal characteristics of the winter SWE obtained from the CMIP6 model simulations and observations were analyzed through the Empirical Orthogonal Function(EOF)analysis.The findings suggest that only some CMIP6 models can reproduce the main features of the first eigenvector,whereas MME can reproduce it well.Moreover,MME can reproduce the response of Eurasian SWE to precipitation and surface air temperature during winter.The projection of Eurasian winter SWE in the 21st century was estimated using the CMIP6 MME results under different emission scenarios of Shared Socioeconomic Pathways(SSPs).With regard to the reference period 1995–2014,SWE projections by MME under four scenarios(SSP126,SSP245,SSP370,and SSP585)all exhibited an increasing trend in the northeastern Eurasia continent and a decreasing trend in continental Europe to the west of 90°E.There was minimal difference in SWE variation under the four SSPs in the early 21st century.However,the difference increased in the late 21st century.Further,the amplitudes of the SWE variations and the intermodel uncertainty increased with time.Further analysis revealed that higher temperatures and increased precipitation were conducive to the SWE increase in northeastern Eurasia.