Autumn Eurasian snow depth, autumn Arctic sea ice cover and East Asian winter monsoon

Abstract

ABSTRACTWe present observational evidence and model simulation demonstrating a significant change in the early 1990s in the relationships of the autumn Eurasian snow depth (AESD) and the autumn Arctic sea ice cover (ASIC) with the East Asian winter monsoon (EAWM). A weakening of the AESD–EAWM relationship occurs over a period when the ASIC–EAWM relationship strengthens. The possible physical process can be described as follows: before the early 1990s, the positive AESD anomaly tends to persist into winter. In contrast, after the early 1990s, the negative ASIC anomaly tends to excite a stationary Rossby wave across the North America–Atlantic sector in autumn. This wave train propagates eastward in winter and favours the winter Eurasian snow depth (WESD) increase. The WESD anomaly is associated with the strengthening and expansions of the Siberian high west and north across the pole and the zonally elongated cold anomalies from Europe to the Far East. It has a stable connection with the EAWM throughout the period observed (1979–2006) and may serve as a bridge linking AESD or ASIC with the EAWM.