Snowline Chang Rule And Its Impact On Snowmelt Runoff In Alpine Regions

In order to understand snow line variation and snowmelt runoff process in high and cold mountainous areas,we should better guide the rational development and utilization of ice and snow water resources,in this paper,the Kashi River Basin in the Western Tianshan Mountains was taken as the research area.Based on MODIS,DEM and meteorological data,the snow line variation rule in mountainous area was analyzed;Based on the daily precipitation,temperature and runoff data of the urapi hydrologic station,the SRM model was constructed to analyze the applicability of the model in the study area;Based on the future data of daily temperature and precipitation of CMIP5,the runoff changes under future scenarios were analyzed with the help of BP neural network,linear regression,and the changes of runoff under the assumption is analyzed in combination with the changes of snow line height.Through the DEM data,the 2000-2016 year MODIS data and the meteorological data,the snow line method,the climate snow line method and the snow line field method were used to analyze the data.It was found that the average annual snow line of 8 days and the annual average of the 2000-2016 years were on the rise;on the seasonal scale,the snow line in spring and winter was on the rise,and the snow line in autumn and summer declined.According to the climate data,the annual snow line has a better response to the precipitation,and the snow line in spring has a good response to the temperature;the climate snow line was higher than the remote sensing monitoring snow line.The difference values of each year's two kinds of snow lines changed year by year,the maximum difference was 1005.75 m.Only from the climate angle,the climate change led to the rising trend of the snow line year by year;the distribution of the snow line in the snow line was mainly affected by the topography.With a height of 2000 m,the upper and lower snow lines had different responses to precipitation.Through 1990-2000 years of hydrological and meteorological data,with the help of SRM model,the parameters of the model were calibrated and the snowmelt runoff process was simulated.The determination coefficients and volume differences of model rates were 0.83 and 6.81% respectively,and the validation periods were 0.82 and 12.69% respectively,it showed that the model has good applicability in this study area,and the simulation effect obtained by the driving model of actual snow cover rate was better than the average snow cover rate of years.By means of reanalysis data and scenario analysis,the variation of snowmelt runoff under hydrological,meteorological data and snow cover data were analyzed,Under the snow line changed scenario,the increased of the flow rate of 100 m and 200 m was 1.63% and 0.14% respectively,and the decreased of the snow line by 100 m and 200 m was 19.72% and 33.92% respectively.The runoff in the spring and summer in the river basin was greatly affected by the changed of snow line.The increased of runoff caused by the change of snow line in July was the most significant.Downscaling models combined with multimode super ensemble prediction and intra linear regression had better revisions to CMIP5 data.The analysis of the climate change rule in the past 2015-2039 years showed that precipitation and temperature increased on the annual scale.On the seasonal scale,precipitation decreased in summer and autumn,and the annual runoff and flood season runoff simulated by the driving model were rising,and the runoff increased more significant under the climate snow line.