Interdecadal Changes in the Interannual Variability of the Summer Temperature over Northeast Asia

This study reveals the interdecadal changes in the interannual variability of the summer temperature over Northeast Asia (NEA), which presents an enhancement around the early 1990s and a reduction after the mid-2000s. The stronger NEA temperature variability after the early 1990s is favored by the enhanced influence of the Pacific-Japan (PJ) teleconnection, which is remotely modulated by the southeastern tropical Indian Ocean (SETIO). After the early 1990s, the mean state over the SETIO presents relatively warmer SST and ascending motion, favoring a good relationship between the local SST and convection. Therefore, the SETIO SST could prominently influence the local convection and subsequently modulate the convection over the western North Pacific (WNP) via a cross-equatorial overturning circulation. The abnormal convection over the WNP further triggers the PJ teleconnection to influence NEA. However, these ocean- atmosphere processes disappear before the early 1990s. In this period, the mean state over the SETIO features relatively colder SST and subsiding motion, accompanied by a poor relationship between the local SST and convection. Therefore, the variability of convection over the SETIO is weak, and thus the atmospheric variability over the WNP is also weakened and the PJ teleconnection presents a different distribution that could not influence NEA. The reduced variability of NEA temperature after the mid-2000s is related to the feeble influence of the PJ teleconnection and the reduced variability of the SETIO SST, which is modulated by the SST over the tropical central-eastern Pacific during the preceding winter to spring.

Automated summary

This study uncovers the changes in interannual variability of summer temperature over Northeast Asia, showing a strengthening after the early 1990s and a reduction after the mid-2000s, which are influenced by Pacific-Japan (PJ) teleconnection and southeastern tropical Indian Ocean (SETIO). The weakened atmospheric processes before the early 1990s lead to reduced variability in Northeast Asia temperature, with weak influence of PJ teleconnection and reduced variability of SETIO SST after the mid-2000s.