Mechanism for the Correlation of Winter Fresh Snow Extent over Northern Eurasia and Summer Climate Anomalies in China: Anomalous Seasonal Transition of Land as a Bond

Using the National Snow and Ice Data Center (NSIDC) snow cover and snow water equivalent data, monthly four-layer soil temperature from ERA40 reanalysis dataset, the mechanisms of the linkage between the Winter Northern Eurasian Fresh Snow Extent (winter TFSE) and subsequent summer climate anomalies in China are investigated. Correlation analysis shows that, the consistent seasonal evolvements of land anomalies act as a bridge for the lag correlation. A large winter TFSE is followed by a slower northeastward retreating progress of snow and frozen soil over northern Eurasia. Consequently, in summer, snow and frozen soil over East Asian middle and high latitudes melt more intensively, the soil temperature correspondingly gets lower than normal, which influences local temperature by cooling and by influencing local meridional wind, and through enhancing East Asian jet, is related to the subtropical high in the western Pacific, even climate anomalies in China, and vice versa. As well as local variations of land factors over East Asian middle and high latitudes are concerned, the signal of winter TFSE is significantly strengthened during snow-and-frozen-soil melting process.