Abstract
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.
Highlights
TP snow can exert profound impacts on local energy budgets and hydrological processes owing to its specific high elevation, emissivity, reflectivity and low thermal conductivity (Dickson 1984; Yasunari et al 1991; Xiao and Duan 2016; Wang et al 2019)
The current literature which examined the impacts of preceding Tibetan Plateau snow cover (TPSC) anomaly (TPSCA) on ensuring downstream climate systems have highlighted the remarkable discrepancies of TPSC anomaly (TPSCA) located over the eastern and western TP, respectively
We investigate the interdecadal-changed effect of TP snow cover (TPSC) on spring precipitation over eastern China (SPEC) around 1990
Summary
TP snow can exert profound impacts on local energy budgets and hydrological processes owing to its specific high elevation, emissivity, reflectivity and low thermal conductivity (Dickson 1984; Yasunari et al 1991; Xiao and Duan 2016; Wang et al 2019). The temporal correlation coefficients (TCCs) with a 17-years sliding window, applied onto the western and eastern TP snow cover indices, add support to such interdecadal change in the western-eastern TPSCA relationship due to an abrupt increasing of TCCs from negative correlation before 1990 to positive after 1991 (Fig. 1c). Upon examination of the regression maps of SPEC anomaly by removing the influence of ENSO (Fig. 4c and 4d), the results bear a strong resemblance to Fig. 4a and 4b, indicating that ENSO may have limited influence on the interannual linkage between the TPSCA and SPEC in the present case Another sequent and interesting question is whether the SPEC experiences an interdecadal shift around 1990. The role of TPSCA on the anomalous SPEC pattern before and after 1990 would be addressed
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