Interdecadal change in the linkage of early summer sea ice in the Barents Sea to the variability of West China Autumn Rain

As the last rain season in China, "West China Autumn Rain" (WCAR) often causes floodings and secondary disasters, severely damaging the economic society. Therefore, the variability of WCAR is an important issue for disaster prevention and mitigation. This study addressed the linkage of the WCAR variability to the early summer sea ice concentration in the Barents Sea (BSIC) over the course of 1961-2020. It is found that their relationship changes from a significant negative correlation to an insignificant one since the early 21st century. During 1961-2002, the reduction in early summer BSIC can induce anomalous warming of autumn surface air temperature over the Barents-Kara Seas through altering the surface heat fluxes. The resultant warming further triggers a meridional wave train extending from the high latitudes southeastward to the western North Pacific via the region of Lake Balkhash and Lake Baikal, leading to a northward displacement of the East Asian jet, a deepening of the Lake Balkhash trough, and a strengthening of the western North Pacific subtropical high, which favor the increase of WCAR. During 2003-2020, however, the surface thermal anomaly in autumn associated with the reduction of early summer BSIC shifts to the western flank, due to decreased climatology and interannual variability of BSIC. Correspondingly, it yields a westward-located meridional wave train, which fails to affect the above WCAR-related atmospheric circulations and hence the variability of WCAR.