Tibetan Plateau Booster Effect on the Influence of Atlantic Multidecadal Variability on the East Asian Summer Rainfall

Abstract

Although influences of the Atlantic multidecadal variability (AMV) and atmospheric heat source over the Tibetan Plateau (TPHS) on the East Asian summer rainfall (EASR) have been previously investigated, the relationship between the AMV and TPHS, and their synergistic impact on the EASR are still unclear. We investigate the distinct relationship between the AMV and TPHS, and the role of Tibetan Plateau (TP) in the impact of AMV on the EASR in this study. Results show that the AMV exerts a remote effect on the EASR through an atmospheric teleconnection, and the TP serves as a booster of this remote effect. The warming of the North Atlantic (positive phase of AMV) enhances the Asian summer monsoon through a zonal wave train along the northern mid-latitudes, yielding an anomalous tripole rainfall pattern over East Asia. The enhanced warm and moist monsoon airflow converges and climbs up along the southern and eastern flanks of the TP, resulting in stronger latent heating over the TP than over other regions along the same latitude due to the orographic effect of the huge plateau. The enhanced TPHS in turn further strengthens the summer monsoon and the East Asian tripole rainfall pattern by exciting a downstream meridional wave train. When the AMV and TPHS are in-phase, the zonal wave train originating from the North Atlantic is strong and propagates eastward to the Asia–Pacific regions, significantly regulating the East Asian summer monsoon. Notably, the TP boosts this remote impact of the AMV through the effect of superimposition.