‘‘Mega-sandwich pattern” of interdecadal precipitation variations and itsregional manifestation in the Asian summer precipitation region

The Tibetan Plateau (TP) is an important link between the South Asian monsoon region, the East Asian monsoon region, and the drylands of Central Asia. Climate changes within these regions are dominated by both the monsoon and the westerlies with precipitation primarily concentrated in the summer. Although previous research has examined the characteristics of interdecadal precipitation variations in these regions, the interconnectivity among these variations remain underexplored. Here, we summarize the current understanding on precipitation variations, with the aim of elucidating the interconnections among regional interdecadal precipitation variations from the perspective of the Asian summer precipitation region. Recent research has identified a "North-South dipole pattern” of precipitation variations across the TP over the past few decades, characterized by increased precipitation in the northern TP and decreased precipitation in the southern TP. This regional pattern is a manifestation of a broader "Mega-sandwich pattern" of interdecadal precipitation variations in Asian summer precipitation. The "Mega-sandwich pattern" includes the North-South dipole pattern in High Mountain Asia, the "Westerlies-dominated climatic regime" in mid-latitude Asia, and the "South Flood (Drought) and North Drought (Flood)" pattern in the East Asian monsoon region. This pattern not only exists at the present day under rapid global warming, but also that it may have occurred throughout the Holocene. Future research on the "Mega-sandwich pattern" of precipitation changes in the Asian summer monsoon region should focus on larger spatial and longer temporal scales, leveraging extensive paleoclimate records, modern observational data, and high-resolution climate models to deepen our understanding of its characteristics and underlying mechanisms.