资源环境科技发展态势分析平台

We employ the fifth generation of the European Centre for Medium-Range Weather Forecasts Reanalysis to investigate the leading mode of the East Asian zonal wind and the contribution of associated climatic factors in boreal winter during 1979–2020. The dominant mode, accounting for 46% of the explained variance, indicates that the East Asian subtropical jet (EASJ) and East Asian polar frontal jet (EAPJ) are meridionally displaced in opposite directions. The corresponding first principal component (PC1) shows clear interannual and interdecadal variations, with a regime shift in the year 1997. The dominant mode is significantly related to the Niño3.4 sea surface temperature (SST), the Barents–Kara Seas (BKS) sea ice concentration (SIC), the Arctic Oscillation (AO) and the Tibetan Plateau (TP) surface air temperature (SAT) on interannual and interdecadal timescales. Multiple linear regression with these variables reproduces PC1 well. The interdecadal variation of PC1 is dominated by the BKS SIC and Niño3.4 SST. The Niño3.4 SST explains more than half of the variance of PC1 on an interannual time scale, which is more than all of the other factors combined. The El Niño phase and BKS SIC are associated with the distance between the EASJ axis (EASJA) and the EAPJ axis (EAPJA). The AO and TP SAT may influence the meridional migration of the EASJA and EAPJA, respectively. The distance between the EASJA and EAPJA also depends on the configuration of the southern Asian cyclone and Siberian anticyclone.