An Interdecadal Enhancement of the Impact of ENSO on the Summer Northeast Asian Circulation around 1999/2000 through the Silk Road Pattern

Abstract

In this study, we find that the negative relationship between El Niño–Southern Oscillation (ENSO) and summer Northeast Asia (NEA; 30°–50°N, 110°–140°E) circulation, especially the geopotential height anomalies in the upper troposphere (H200), is weakened from the early 1970s, remains stable since the middle 1980s, and is strengthened dramatically after 1999/2000. The recent transitions of the ENSO–NEA H200 relationship are closely connected with the variation of circumglobal teleconnection (CGT)/Silk Road pattern (SRP), which is further modified by the interdecadal shift of the ENSO–Indian summer monsoon rainfall (ISMR) relationship and ENSO evolution. During 1980–99 when the continuing ENSOs dominate, the weakened ENSO–ISMR relationship leads to an inactive ENSO-related CGT/SRP wave train in the upper-level troposphere and then a weakened connection between ENSO and H200 over the NEA. On the other hand, when the emerging ENSOs dominate after 1999/2000, the restored ENSO–ISMR relationship reinforces the ENSO-related CGT/SRP wave train and then enhances ENSO–NEA H200 relationship. This mechanism is well simulated in the Atmospheric Model Intercomparison Project models (AMIP) and Pacific Ocean–Global Atmosphere (POGA) experiments.