The Influence Of Spring Snow Cover In Eurasia On Interannual Variation Of Spring Precipitation Over Southern China

Observed data show that most of the snow cover in Eurasia is concentrated in mid-high latitude region in winter and can persist until the following spring.Snow cover albedo effect and hydrological effect have significant influence on climate change.In this paper,the observed monthly mean precipitation data from 160 weather stations in China provided by China meteorological administration;NCEP-NCAR reanalysis data;snow cover data and a simple linear baroclinic atmospheric general circulation model(LBM)from Japan are utilized to discuss the possible mechanism of the influence of spring snow cover extent(SCE)over Eurasia on the interannual variability of spring precipitation over southern China during the period of 1972 to 2009.The results show that there is a significant positive correlation between the spring snow anomalies near Lake Baikal and its surrounding areas and the interannual variability of spring precipitation over southern China.When the SCE is positive anomalies around Lake Baikal,there is abnormal southerly winds over southern China.It brings water vapor from the low latitude of Northwest Pacific Ocean and converges over southern China,which leads to the positive anomalies of spring precipitation over southern China.In addition,the numerical results of a simple linear baroclinic atmospheric general circulation model(LBM)show that the snow anomalies over the Eurasian region of Lake Baikal can affect the spring precipitation over southern China by affecting the atmospheric circulation anomalies in East Asia and the region of Northwest Pacific Ocean.Further studies indicate that spring precipitation over southern China shows a decrease since the end of 1980s.Meantime,the interannual variability of spring precipitation anomalies over southern China is from active phase to stable period.During this period,the snow cover extent(SCE)anomalies around Lake Baikal and its surrounding areas also experience a change from positive phase to negative phase.According to the results mentioned above,the whole dataset is divided into two periods,1972-1987(P1)and 1988?2009(P2).The results show that,during P1,the SCE anomalies around Lake Baikal are consistent with the regional mono-sign of positive precipitation anomalies over southern China,which is similar to the first leading mode(PRE_EOF1)of the empirical orthogonal function(EOF)of spring precipitation over southern China.During P2,the snow cover extent(SCE)anomalies around Lake Baikal are in favor of the spring precipitation anomalies of the north-south dipole modes over southern China.Its spatial distribution is characterized by positive precipitation anomalies in the Huai river basin and Yangtze river and negative anomalies in the region of pearl river delta,which is similar to the second leading mode EOF(PRE_EOF2)of spring precipitation anomalies over south China.Furthermore,we study the relationship between the North Atlantic SST anomalies and the SCE anomalies in Eurasia.The results show that there is a significant correlation between the North Atlantic SST dipole in the early winter of December and the interannual variability of spring SCE anomalies in Eurasia.After the end of 1980s,the contribution of the North Atlantic SST dipole to spring SCE anomalies in Eurasia has weakened.