Spatial And Temporal Characteristics Of Snowmelt Across Eurasia From 1966 To 2011

Snow,as an important part of the cryosphere,has been deeply affected by climate change in the past decades.Snow accumulates on the surface in the form of solid state and stores the fresh water resources that people depend on for survival in high latitude and high altitude areas.The melting process of snow is complicated,which turns into groundwater or surface runoff and becomes the available water resource.Climate warming first threatens the amount of snow water resources,and directly affects the temporal and spatial changes of snow melting characteristics?including snow melting time,snow melting rate?.It is of great importance to the utilization and planning of the snow-melting water resources,the flood forecast of snow,and the ecological hydrological process.The past research of snow melting process from in situ measurements is not enough to solve the macro problem caused by the melting of snow in the region,and the uncertainty and accuracy of the spatial resolution caused by the satellite remote sensing and model simulation result in the inherent defects of the research on the macro-snow water resource.This paper analyzes the characteristics of macro-melting snow,such as the first day of melting,the duration of melting,the rate of melting,and degree-day factors of melting based on the long-time series of snow and air temperature data of 1255 meteorological stations in Eurasia.Based on the runoff data of major rivers in Eurasian arctic region,the relationship between snow melting and runoff is analyzed.The results are as follows:?1?The first day of the snow-melting period from 1966 to 2011 in the Altai station in Xinjiang was on March 11,the average snow-melting period was 17 days,the first day was advanced at a rate of 0.29 days/year,and the snow-melting period was extended at a speed of 0.25 days/year,but the snow-melting rate did not change significantly.The decrease of radiation during the snow melting period explains that the snowmelt degree day factors reduction in the rate of-0.0073 mm·?^-1d^-1yr^-1.?2?Snow melting in southern Eurasia began at the end of February and ended in the middle and early March.Snow melting in northern coastal areas ended at the end of June at the latest.The duration of snow melting showed the spatial distribution characteristics of"first increasing and then shortening"with the increase of latitude.The first day of snow melting at some stations was significantly advanced at the speed of 0.18 days/year to 0.62 days/year,and the last day of snow melting at some stations was significantly advanced at the speed of 0.5 days/year.The overall change of snow melting in Eurasia is not significant.?3?The rate of snow melting in Eurasia is as low as 2.54 mm/day at low latitudes and as high as 13.48mm/day at high latitudes.Snow melting rate at some stations accelerated significantly at a rate lower than 0.09 mm.d^-1yr^-1.?4?The degree day factor of snow melting degree is below 1.07 mm·?^-1d^-1 in central Europe and southern Siberia,while it is above 2.15mm·?^-1d^-1 in the northern coastal and southern fringe of snow-rich areas.The spatial distribution characteristics of stations with significant daily variation of snowmelt intensity are not obvious.?5?The spring runoff of the Yenisei,Lena and Obi rivers shows a significant increase trend,which is consistent with the results of temperature rise and snow melting ahead of schedule.The runoff growth rate of the Lena and Obi rivers is about 20 m³s^-1yr^-1 from January to April.The monthly runoff increase rate of the Yenisei River in spring reaches more than 90 m³s^-1yr^-1.The increase of snow melting in spring leads to the decrease of runoff in summer.The runoff decrease rate in July reaches-84.14 m³s^-1yr^-1.