Linkage Of Anomalous Snow Water Equivalent Over The Eurasian Continent With Spring And Summer Climate In China

Using the average monthly global snow water equivalent data during1979-2007provided by the Snow and Ice Data Center in the United States, the NCEP/NCAR monthly reanalysis data, an index used to reflect the spring snow water equivalent increment was defined, which can more directly reflect the situation of the spring snowmelt. The possible linkages between the winter and spring snow over the Eurasian Continent, and the influence of spring snow water equivalent increment on the climate over China are investigated, and preliminary discussion of the mechanism of the spring snow affect our climate are given. The main conclusions are as follows:1) By analyzing the spatial and temporal characteristics of the Eurasia winter snow water equivalent and its increment in spring, it is found that the first EOF modes of both winter snow water equivalent and its spring increment exhibit a consistent variation over most area of the Eurasian continent except fot the eastern part of Eurasia. Significant inter-annual variations of their time coefficients are detected, and abrupt changes are found in the late1980s. However, the second EOF modes reflect east-west dipole pattern over the whole Eurasian Continent.2) The leading EOF modes of both the winter, spring snow water equivalent increments show that the correlation coefficient between the time series of the two leading EOF modes is0.92,which is statistically significant at0.01confidence level. And the correlation coefficient between the time series of the two seond EOF modes is0.43, which also shows close relationship between them. By comparing the features of the spatial and temporal variations of winter and spring snow water equivalent increments, their spatial and temporal features in spring can persist till spring.3) On the whole, Influence of winter and spring Eurasian snow water equivalent on the climate in summer in China is more significant than that in spring, which suffesting an evident lag effect of the snow cover. From winter to spring, areas with significant correlation evident increases, indicating that the effect can persist from winter to spring, thus affect summer climate in China. 4) Anomalous spring snow water equivalent over the Eurasia can significantly affect the500hPa height and temperature fields in the same period. When consistent variations in the snowmelt over the whole continent happens, the anomalies of spring500hPa geopotential height over the mid-high latitude of East Asia is featured by a "-+-+" wave-train like spatial pattern, and significant negative correlation was found in the Northeast China. However, when there is an out-of-phase pattern in spring snowmelt over the Eurasian continent, EU-like teleconnection pattern appears over the Eurasian continent.5) When more (less) spring snowmelt takes place, the summer geopotential height over Northeast China tends to be reduced, and the converge of the cold air and the southwest airflow as well as the water vapor convergence in Northeast China will result in more (less) precipitation and lower (higher) temperature in summer in Northeast China.6) When there is an out-of-phase pattern in spring snowmelt over the Eurasian continent, i.e., more (less) spring snowmelt in European but less(more) snowmelt in the Siberian, the westward extension of the summer subtropical high tends to be strengthened (weakened). Located in convergence (divergence) zone of the warm and humid air, the Yangtze River basin usually accompanied by more (less) precipitation.