Linkage of the preceding winter mid-latitude Eurasian atmospheric circulation with the spring northern East Asian snow cover

Abstract

Within the current study, the linkage between the preceding wintertime atmospheric circulation around the mid-latitude Eurasia (MLE) and spring Asian snow cover is detected. The result suggests that following the primary atmospheric mode over the MLE during winter, the positive snow cover anomalies tend to appear over northern East Asia (EA) in the ensuing spring. This primary atmospheric mode featured by the negative–positive–negative anomalous geopotential height centers in the middle level around the MLE is conducive to the zonal wavenumber-1 component (ZWN-1) propagating upward into the stratosphere in winter. The poleward heat transportation anomalies connected with the strengthened upward wave activity contribute to the significant anomalous stratospheric warming and thereby a weaker than normal lower stratospheric polar vortex during spring. This abnormal lower stratospheric polar vortex then propagates downward and generates a significant tropospheric cyclonic anomaly around Lake Baikal, favoring the anomalous cooling and more snowfall over the region. The above condition finally results in the enhanced spring snow cover around northern EA. Moreover, the observed connection shown above can be reproduced in the historical simulation (1979–2014) of some coupled models of the Coupled Model Intercomparison Project Phase 6 (CMIP6). The result also implies that the time series corresponding to this primary atmospheric mode exhibit a potential to predict the spring snow cover over northern EA.