Temporal And Spatial Distribution Characteristics Of Eurasia Snow And Its Associations With East Asia Climate Change

In this study, the temporal and spatial distributions of Eurasia snow change are analyzed, and the relationship between Eurasia spring snow and China spring and summer rainfall is also investigated with data of SSM/I snow cover fraction, SMMR snow depth, snow water equivalent, former Soviet Union snow depth, Eurasia snow cover extent and 160 stations rainfall of China. Furthermore, the possible mechanism of snow affecting China summer rainfall and East Asia climate is discussed, and additional numerical modeling experiments are carried out to verify results of diagnostic analysis. The main conclusions are as follows:Eurasia snow cover extends from northeast to southwest during the autumn, and reduces from southwest to northeast during the spring. During the winter and spring, Eurasia snow cover has a large variation rate in western Eurasia and Tibetan Plateau, but Eurasia snow depth and its variation rate are both large in high latitude central and eastern Eurasia.EOF analysis of former Soviet Union snow depth indicates that variations of snow depth in western and eastern Eurasia are in the opposite phases during the winter and spring. In the EOF analysis of Eurasia snow water equivalent, the leading mode shows that snow water equivalent in most Eurasia varied similarly, which experienced an interdecadal variation in the late 1980s, meanwhile, spring Eurasia snow cover extent also experienced an interdecadal variation.Snow cover extents of neighboring months are well positively correlated. Snow water equivalent has high persistence from winter to spring, whereas persistence for snow cover extent is low. In high latitude Eurasia, snow cover extent and snow water equivalent are well positively correlated.In general, spring rainfall in southern China is positively correlated with spring Eurasia snow water equivalent and snow cover extent. Summer rainfall in Yangtze River region is positively correlated with spring Eurasia snow water equivalent and snow cover extent, whereas summer rainfall in southern China is negatively correlated with that. When there is more rainfall in Yangtze River region and less rainfall in South China during the summer, spring surface temperature is low in middle Eurasia, and spring 500 hPa height is also low in middle Eurasia and western Europe, but high in mid-east Eurasia; summer surface temperature is low in north and northeast China, so is summer 500 hPa height in mid-high latitude East Asia, but high in southern China.Spring snow cover extent and snow water equivalent can significantly affect spring surface temperature and 500 hPa height. In the years of more snow, surface temperature is low as well as 500 hPa height in middle Eurasia and Western Europe, but high in Mid-eastern Eurasia.Spring snow cover extent and snow water equivalent can indirectly affect summer atmospheric circulation and rainfall. In the years of more snow, summer 500 hPa height is low in south China, but high in south China.The numerical experiment results show that, when Eurasia has more snow, south China has more rainfall during the spring and less rainfall during the summer, and north China and northeast China also have more rainfall during the summer, which is consistent with diagnostic analysis.