关键词: 积雪, CMIP5, 预估

Abstract: Based on the dataset observed by the meteorological satellites from NOAA, the simulated Northern Hemisphere March-April snow cover fraction (SNC) in historical experiments from 23 coupled climate models attending the fifth phase of the Coupled Models for Inter-comparison Project (CMIP5) was evaluated. The 23 models were aggregated by arithmetic mean to project the changes of Northern Hemisphere March-April SNC in 2006-2099. The results show that, overall, the CMIP5 coupled models reproduce the observed snow cover extent well and catch the main characteristics in the distribution of snow cover. But the simulation of snow cover in complex terrain area such as Qinghai-Tibet Plateau is poor and the significant trend towards a reduced spring snow cover extent over 1979-2005 is underestimated. The defect of satellite data and differences of parameterization schemes used in different models may be the causes. The projection by multi-model ensemble show that, the snow cover will continue to reduce in the next few decades mainly in the central and western regions of Eurasia. Greenhouse gas emissions will have a significant impact on the change of Northern Hemisphere snow cover in the future. The northern Hemisphere snow cover will reduce the most significantly under RCP8.5 scenario. Under RCP4.5 and RCP6.0 scenarios, the reduction of snow cover is equivalent to that under RCP8.5 scenario in the first half of the 21st century, but the decreasing trend is significantly less than that under RCP8.5 scenario in the last half of the 21st century. Under RCP2.6 scenario, the reduction of snow cover will not be significant. Therefore, it is crucial to control the discharge of greenhouse gas emissions for mitigating the disappearance of snow cover over Northern Hemisphere.

Key words: snow cover, CMIP5, projection