Study The Ratio Of Snowfall To Rainfall During 1961-2013 And The Future Trend Prediction In Xinjiang

The ratio of snowfall to rainfall, just as its name implies that the ratio of snow and rainfall. Under global warming during the last decades, the proportion of rain and snow change with water circulation and precipitation type. The form of precipitation(solid or liquid) has different impact on regional water resources and their annual distribution, because such change could influence the timing of spring runoff and cause water shortage in summer. In this paper, based on 699 daily precipitation and temperature from gridded datasets, and 51 meteorological stations in Xinjiang during 1961-2013 released by National Meteorological Information Center, the reliability of gridded dataset in Xinjiang are verified and the trend magnitudes of the proportion of precipitation occurring as snow are analyzed. The temporal variation and spatial distribution of the ratio of snowfall to precipitation in Xinjiang are studied. The ratio of snowfall to precipitation in Xinjiang in future is predicated by RCP4.5 using the IPCC Fifth Assessment Report. The results are given as follows:(1)The bias of interpolated gridded dataset and observation at most stations shows less and the correlation shows better. The bias of 51 observation stations mainly concentrates between 0.2mm and 1.0mm(72.55%). The correlation coefficients are generally above 0.75 in most region(84.31%). So the dataset can be used to investigate the proportion of rain and snow in Xinjiang.(2)The proportion of precipitation occurring as snow is decided by the amount of snowfall and rainfall. The trend of snowfall and rainfall during 1961-2013 shows an increasing trend, in which the increasing trend of snowfall is not obvious by 0.11mm·a-1, but is not statistically significant at 0.05 level. The rainfall increases by 0.62mm·a-1, and is statistically significant at 0.0001 level. The mutation of rainfall in Xinjiang happened in 1990, while sonwfall has no obvious abrupt. From spatial distribution, the increasing or decreasing trend of snowfall and rainfall in Xinjiang show significant difference.(3)The proportion of precipitation occurring as snow change in Xinjiang during 1961-2013 shows increasing trend by 0.001·a-1, but is not statistically significant at 0.05 level,which has no obvious abrupt and periodic variation shows significant. From spatial distribution, the decreasing trend in southern Xinjiang shows more significant than in northern Xinjiang, in which the increasing trend shows in some parts of the Altai Mountains, Harlik Mountains, and some parts of basin of Aksu River, but the decreasing trend is in Kunlun-Altun Mountains.(4)The RCP4.5 scenario of the IPCC Fifth Assessment Report predicates that snowfall and rainfall of Xinjiang in the future may decrease and increase, respectively, in which snowfall and rainfall may decrease and increase with largening of carbon emission, respectively. The spatial distribution of snowfall, rainfall and the proportion of snowfall and rainfall shows little difference, in which Kunlun-Altun Mountains shows much more obvious than in other regions.