Snowmelt Runoff Simulation Based On Coupled Atmospheric-Hydrological Modeling In Alpine Regions

In order to improve the simulation accuracy of snowmelt runoff in the alpine areas and better guide the sustainable development and utilization of water resources in the glacial snowmelt areas,and the yili river basin as a typical research area.the meteorological simulation results of the Weather Research and Forecasting(WRF)model with high resolution simulation accuracy were used to drive the distributed Variable Infiltration Capacity(VIC)hydrological model,and the data assimilation technology was used to improve the accuracy of meteorological simulation in the WRF model.The WRF-VIC atmospheric-hydrological coupling model based on the data assimilation correction is constructed to carry out snowmelt runoff simulation research in alpine mountains.The GFS reanalysis data as the initial conditions of WRF model,selection 14 physical parameterized combination scheme,and the double-layer nesting method of 9km:3km was used to simulate the precipitation and temperature in the study area over three periods.The results showed that:(1)The simulation results of 14 different combinations of schemes in WRF mode and the measured values by comparing the root-meansquare error,standard deviation ratio and mean error between,it is found that scheme a(LIN-EX-MYJ)is the best combination schemes for rainfall and temperature simulation;(2)The WRF model underestimated the measured precipitation and average temperature in the study area.The average error of rainfall per hour for the three events was-0.24 mm,-0.15 mm and-0.02 mm,and the average error of temperature was-2.96?,-3.49? and-2.23?.With the help of NCEP ADP sounding data and NCEP GDAS satellite data(including ATOVS,MHS and AMSUA),the precipitation and temperature of WRF simulation results were assimilated in different nested forms.The results showed that the simulation accuracy of WRF model was improved by the three nested assimilation schemes and the four observation data assimilation schemes,among which ADP sounding data the assimilation two-layer nested scheme(D01+D02)improved the most,the root mean square error of precipitation decreased from 0.75 mm to 0.64 mm,and the root mean square error of average temperature decreased from 3.49? to 1.29?.Based on the characteristics of the ERA-Interim and the measured precipitation data different precipitation correction methods were used to correct the ERA-Interim data,the results show that the monthly precipitation ratio as the correction coefficient has the best correction effect on precipitation,the monthly average precipitation error reduced from 8.38 mm to-0.26 mm.Assisted ERA-Interim data and three linearly corrected precipitation data to drive VIC hydrological models,respectively,to conduct snowmelt runoff simulation studies.the results show that the monthly precipitation ratio as the correction coefficient has the best correction effect on runoff,the Nash efficiency coefficient and relative error of the monthly scale runoff simulation results were 0.81 and 13.61%,and the Nash efficiency coefficient and relative error of the daily scale runoff simulation results were 0.63 and 9.71%.In order to improve the accuracy of the runoff simulation of the VIC hydrological model in the flood season,the WRF model was used to simulate the meteorological elements in the 2004 flood season(May to August)and the ERA-Interim meteorological data in the 2004 non-flood season were used as the meteorological input data of the VIC hydrological model to construct The WRF-VIC atmospherichydrological coupling model simulates the daily runoff process in the study area in 2004.The results show that the WRF-VIC atmospheric-hydrological coupling model has better simulation results in non-flood season runoff,and the total simulation error value of the whole flood season was-81.85mm;Based on the assimilation results of the WRFDA model in the 2004 flood season(May to August)and the ERA-Interim meteorological data in the 2004 non-flood season as the meteorological input data of the VIC hydrological model,the runoff simulation of the WRFDA-VIC land-air coupling model was carried out.The results show that the data assimilation improves the runoff simulation effect of the WRF-VIC atmospheric-hydrological coupling model in the flood season,and the error is reduced from-81.85 mm to-68.86 mm.