Interannual Variations Of Snow Cover Over China And Possible Changes In Next 40 Years

As a crucial role of cryosphere, snow cover is a very important compenents of climate system. It plays an important role in climate change, because of the high albedo, the cooling effect in melting process, hydrological processes and a particular medium between atmosphere and land. Snow cover widely distributes in our country, and regional and annual variation is significant. In this paper, observational snow depth of 738 meteorological stations in China from 1960 to 2004 is used in the research. The temporal and spatial characteristics of snow cover in the past 40 years are analyzed. The typical regions of interannual anomaly of snow cover are discussed. The next, the simulating capability of snow cover of global climate model (GCM), which joins the Coupled Model Intercomparison Project (CMIP3) is tested in this paper; then we use the method of model ensemble average to prediction the variation characteristics of snow cover in next 40 years in A2, A1B and Bl emission scenarios. Using temperature and precipitation, snow fall is calculated and prediction is made which is also compared with GCM results. The main contents and conclusions are as the follow:1. The characteristics of snow cover over China in the last 40 years are shown.The results show that the southwestern and southern portions of Tibetan Plateau, northern Xinjiang and northeastern China-Inner Mongolia are three regions in China with high seasonal snow cover and also an interannual anomaly of snow cover. According to the trend of both the snow depth and snow cover days, there are 3 changing patterns for the seasonal snow cover:The first type is that both snow depth and snow cover days simultaneously increase or decrease; this includes northern Xinjiang, middle and eastern Inner Mongolia, and so on. The second is that snow depth increases but snow cover days decrease; this type mainly locates in the eastern parts of the northeastern plain of China and the upper reaches of the Yangtze River. The last type is that snow depth decreases but snow cover days increase at the same time such as that in middle parts of Tibetan Plateau. Snow cover in China appears to have been having a slow increasing trend during the last 40 years. On the decadal scale, snow depth and snow cover days slightly increased in the 1960s and then decreased in the 1970s; they again turn to increasing in the 1980s and persist into 1990s. Both snow depth and snow cover days in the three typical regions appears to have been having a increasing trend.2. GCM simulating capability of Snow cover which takes part in CMIP3 is tested and integrate assessment in China.Due to the various spatial resolution of the GCM, the complex topography and underlying surface type and other factors, the simulating capability of GCM are various. The simulating capability of GCM varies in different regions of China with different spatial resolution, complex topography, underlying surface type and some other factors. Considering the spatial correlation coefficient, simulated error, the phase lag, root mean square, time-dependent coefficients and other factors,52 runs of 15 GCMs of snow depth and 71 runs of 22 GCMs of snow water equivalent are comprehensive tested. The results show that simulated capabilities of snow depth and snow water equivalent were limited, and there are some differences in each model. The simulating capability of spatial distribution of snow depth and snow water equivalent is better than temporal variation, and the results in Northern Xinjiang and Northeast China are better than in Tibetan Plateau. The simulated results of snow depth and snow water equivalent in Northern Xinjiang and Northeast China are lower, but the result in Tibetan Plateau is higher, especially in the west of the Tibetan Plateau. CCSM3, CGCM3.1(T47); CSIRO-Mk3.5, INM-CM3.0 and PCM's simulating capability of snow depth are better then other models, and CSIRO-MK3.0,CSIRO-MK3.5,GISS-AOM,CGCM3.1(T47),MRI-CGCM2.3 and HadCM3's simulating capability of snow water equivalent are better then other models.3. The possible change of cumulated snow in next 40 years over China is presentedBased on (2), we estimated the snow depth with the ensemble of CCSM3, CGCM3.1 (T47), CSIRO-Mk3.5, INM-CM3.0 and PCM; we estimated the snow water equivalent with the ensemble of CSIRO-MK3.0, CSIRO-MK3.5, GISS-AOM, CGCM3.1 (T47), MRI-CGCM2.3 and HadCM3. The results show that in the A2, A1B and B1 scenarios, changes of the snow depth and snow water equivalent in next 40 years are consistent. The decreasing change zones mainly locate on Tibetan Plateau, the west of TianShan Mountains, the central and southern Loess Plateau, south of Qinling to middle reach of Yangtze river and the north of Northeastern China; among these region, the most significant decreasing change occurred over the Pamirs on the west of Kunlun mountains; There is a slight increase of cumulated snow over the Inner Mongolia, Tarim Basin, Yunnan Province and some costal areas (Guangxi Province, south of Guangdong Province) in the south of China. Variations of snow depth and snow water equivalent between 2010 and 2050 over China show a decreasing trend, and the most significant region locates on Tibetan Plateau. The decrements of snow depth and snow water equivalent over the Northeast of China and the north of Xingjian Province are less than the Tibetan Plateau. Compared to the annual variations of snow depth and snow water equivalent between 1971 and 2000, in 2021～2050, spring snow will decrease, but in winter half year, it may increase slightly. With the relation among temperature, precipitation, and snowfall, it can be figured out that in the A2, A1B and B1 scenarios, snowfall will decrease in next 40 years as well, especially on the edge of the southern Tibetan Plateau to the Middle and the East. Compared to the period of 2021-2050, snowfall decreases more significantly from January to May during 1971-2000.