Diminished Impact of the East Asian Winter Monsoon on the Maritime Continent Rainfall After the Late‐1990s Tied to Weakened Siberian High–Aleutian Low Covariation

Abstract

AbstractStrong East Asian winter monsoon (EAWM) can enhance the Maritime Continent rainfall (MCR) via frequent southward penetration of cold air along the coast of East Asia. However, such impact diminished after the late‐1990s, primarily due to the weakened covariation between the Siberian high and Aleutian low (AL). During 1979–1998, the co‐variability between the Siberian high and AL facilitates a strong east‐west pressure gradient over East Asia. The resultant northerlies invade southward and facilitate the enhanced MCR. In contrast, such covariation is weak during 2000–2018, and it impedes the southward invasion of northerly winds and diminishes EAWM's impact. Further inspections indicate that the weakened covariation is primarily caused by the reduced variability of the AL. The underlying mechanism is confirmed by the historical simulation of version 6 Model for Interdisciplinary Research on Climate (MIROC6) that participates in phase 6 of the Coupled Model Intercomparison Project and numerical experiments with European Center‐Hamburg atmospheric model version 6.3 (ECHAM6).