Interdecadal Change in the Effect of Tibetan Plateau Snow Cover on Spring Precipitation over Eastern China around the Early 1990s

Previous works extensively investigated the influences of the winter–spring Tibetan Plateau snow cover (TP, TPSC) on climate variability over the East Asia. The present work documents an interdecadal-changed impact of distinct spring TPSC anomaly (TPSCA) patterns on spring precipitation over eastern China (SPEC) around the early 1990s. It is found that the connection between the eastern and western TPSCA shifts from negative correlation to positive one around 1990. The empirical orthogonal function (EOF) analysis applying onto the spring TPSCA during 1970–1989 (P1) and 1991–2017 (P2) provides additional evidence. In detail, the leading EOF (EOF1) mode during P1 shows an out-of-phase pattern with opposite signals over the eastern and western TP, while the EOF1 during P2 is characterized by an in-phase pattern over the entire TP. Corresponding to more (less) snow cover in the eastern (western) TP in P1, a significant TP cold cyclone (TPCC) and a downstream anticyclone over the western North Pacific could be observed. Anomalous southerly flow prevailing east to TPCC could bring the warm–wet air from tropics to the coast of East Asian, which largely enhances the spring precipitation south of the Yangtze River Valley (YRV). By contrast, regarding more snow cover over the eastern and western TP in P2, a relatively more northward-shifted and wider TPCC sweeps over the entire TP, compared with the counterpart in P1. Moreover, during P2, there are significant sinking anomalies observed in the downstream YRV-Huaihe River Valley (YRV-HRV) region, which leads to suppressed spring precipitation over there via the dry–cold advection process. Hence, distinct TPSCA patterns in different epochs may favor an interdecadal shift of the SPEC anomaly pattern around 1990 by inducing local and downstream atmospheric circulation.