The Change Of Snow Cover On The Qinghai-Tibet Plateau And Its Influence On Surface Radiation And Energy Exchange

This paper analyzes the temporal and spatial variation characteristics of snow cover on the Tibetan Plateau from 110 meteorological stations in the Qinghai-Tibet Plateau from September 1,1960 to August 31,2014,and explores the snow depth and snow days.The relationship between factors.Then,using the CLM4.5 land surface model to simulate the Qinghai-Tibet Plateau from 1992 to 2010,the effects of snow cover and snow-covered snow on the radiation and energy exchange of the QinghaiTibet Plateau were studied.Finally,different land surface schemes(CLM4,Noah-LSM,RUC and Noah-MP)in the WRF model were selected for comparative experiments to evaluate the simulation effects of different land surface processes on the snow cover and snowmelt process on the Tibetan Plateau,and provide the most for snow cover simulation on the Qinghai-Tibet Plateau.Good land plan options.The aim is to understand more fully the response of snow cover on the Tibetan Plateau to full warming,and to understand more deeply the impact of snow cover on the Tibetan Plateau on surface radiation and energy exchange.The main conclusions are as follows:(1)During the period from 1961 to 2014,the average annual snow depth and snow cover were 0.26 cm and 23.78 d,respectively,and the spatial distribution was uneven.On the seasonal scale,the average variation range was 0.01~0.53 cm and 0.38~10.87 d.Between d.The large depth of snow is mainly located in the Himalayas and the northern Tibetan plateau.The number of snow days is large in the Bayan Hara area,the Himalayas and the northern Tibetan plateau,and the Bayan Hara area is the largest.In the trend of change,the annual snow depth and the number of snow days showed a slow downward trend,which were-0.00800.0086cm/10a(p=0.36)and-0.640.47 d/10a(p=0.17).Winter snow changes play a major role in the annual snow cover change.The interannual variation of snow cover on the Tibetan Plateau is obvious.The snow depth and the number of snow days show the trend of “decrease-increase-decrease” in the spring,winter and interannual variations,while the fall is the trend of increasing first and then decreasing.The correlation between precipitation and snow depth and snow days is complicated: winter precipitation is highly correlated with snow depth and snow days;autumn and annual precipitation are less correlated with snow depth and snow days.The snow depth and the number of snow days decrease with the height of the sea wave;the number of snow days decreases with increasing latitude.(2)The CLM4.5 land surface model reproduces the spatial distribution of snow cover depth and the variation of snow cover days on the Tibetan Plateau,but the simulated snow depth is too large.In October,the depth of snow and the number of snow days on the Tibetan Plateau began to increase,reaching the maximum in January of the following year(5.60 cm and 17.75d).From February to May,the depth of snow and the number of snow days gradually decreased.The average snow depth in September-September is less than 0.2cm,and the average snow cover days are less than 0.5d.The main snow cover period of the Qinghai-Tibet Plateau is from October to May.On the whole snow cover of the Qinghai-Tibet Plateau,the snow depth and snow days are negatively correlated with net short-wave radiation,net radiation,surface soil heat flux,sensible heat and latent heat,and positively correlated with net long-wave radiation.However,the characteristics of different seasonal scales and different depths are not completely consistent.The snowy years of the Qinghai-Tibet Plateau were 1998,2002 and 2007,followed by the years of 2003,2006 and 2008.The net short-wave radiation,net radiation,sensible heat and latent heat of the snowy years were less than the years of less snow,and the net long-wave radiation was Snowy years are greater than less snow years,and surface soil heat fluxes are less likely to differ between snowy years and less snow years.(3)The WRF model can better simulate the 2m temperature characteristics,but there are also a few moments when the simulated values differ greatly from the observed values.Among the four land surface parameterization schemes selected in this chapter,the CLM scheme has the best simulation results.The WRF model can better reproduce the variation of snow cover time on the Tibetan Plateau,but the deviation increases sharply after 10 days;the ablation rate error is large.The CLM land surface parameterization scheme has a small simulation value of snow depth and snow days,while Noah-LSM,RUC and Noah-MP simulation values are too large;Noah-MP and CLM land surface parameterization schemes respectively for snow depth and snow The water equivalent simulation is the best;using a more realistic snow field can improve the WRF model for 2 m air temperature and snow simulation.