Analysis On Temporal-Spatial Characteristics Of Cumulative Snow Depth And Its Influence Factors In Northeast Of China And Its Vicinity

Base on the snow cover data, meteorology elements data of 123 meteorology stations in Northeast of China and its vicinity, the monthly mean reanalysis data of geopotential height, air temperature, specific humidity and wind fields from NCEP/NCAR, circulation index and The World Climate Research Programme's (WCRP's) Coupled Model Intercomparison Project phase 3(CMIP3) multi-model dataset from National Climate Center. The article analyze the spatial and temporal characteristics of snow cover, the relationship between snow cover and typical meteorological elements, search the key general circulation which plays an important role with snow cover,and try to find the methods of prediction of snow cover in autumn, winter and spring by EOF method,REOF method,SVD method, morlet wavelet analysis and multiple regressions. The main conclusions are as follows:(1) The snow cover in Northeast of China is increasing slowly and has a quasi-period of 7 years in recent 50 years.There are stable snow cover (snow cover days are more than 60 days) and unstable snow cover (snow cover days are between 10 and 60 days) in Northeast of China. Variation of the southern boundary of the stable snow cover is related to precipitation. We hold the opinion that there are three main spatial patterns of cumulative snow depth in Northeast of China by using EOF method, of which, the first pattern is consistently more (less) than normal, the second pattern is a seesaw between southern(northern) region and northern (southern)region, the third pattern is a seesaw between central region (other region) and other region (central region).(2) The snow cover is no obvious changing in autumn, increasing in winter, and decreasing in spring, as snow cover in winter makes up over 70 percent of annual snow cover, so it is the key fator to increasing annual snow cover. In autumn and spring, mean temperature is the key factor for cumulative snow depth, but in winter, precipitation is the key factor. The curve of cumulative snow depth is fitted with mean temperature, precipitation, negative accumulated temperature and snowfall days by multiple regressions. It is useful for simulation and forecasting of the snow cover. (3) Arctic Oscillation is the key general circulation for snow cover in autumn and spring.The AOI is negative phase, while the area of polar vorticity is larger than the same period of normal years, the cold air is stronger, the mean temperature in Northeast of China is lower, snow cover in autumn and spring is heavier, and vice versa. The SST in Kuroshio current region has an obvious positive relation with snow cover in winter by air-sea interaction, when the SST in Kuroshio current region is higher than the same period of normal years, the air temperature and geopotential height over Kuroshio current region are also higher, while the East Asian trough and cold air are stronger, and the stronger SST in Kuroshio current region can bring more water vapor to Northeast of China, snow cover in winter is heavier than normal years, and vice versa.(4) The mean temperature and precipitation in Northeast of China will increase in the 21st.The increasing of mean temperature and precipitation in winter is more obvious than in autumn and spring. The snow cover in winter will increase, the snow cover in autumn and spring will decrease in the future, and it's more obvious under SRES-A2 than SRES-A1B and SRES-B1.