The Role of Local Wave Activity in Influencing Extreme Precipitation Patterns Over North and Northeast China

Abstract

ABSTRACT Warm‐season extreme precipitation over North and Northeast China is a major regional hazard and is strongly influenced by large‐scale atmospheric circulation. However, how large‐amplitude wave activity varies among different spatial patterns of extreme precipitation remains insufficiently understood. Using precipitation observations and atmospheric reanalysis data for May–August 1961–2024, this study investigated the spatial patterns of extreme precipitation using a structural self‐organising map and examined their large‐scale circulation characteristics within the local finite‐amplitude wave activity (LWA) framework. Four dominant precipitation patterns were identified, with their primary precipitation centres distributed progressively farther south from Northeast China to the Jiang–Huai region. These meridional differences were accompanied by corresponding shifts in both the mid‐tropospheric troughs and enhanced LWA, with the precipitation centres consistently located on the equatorward side of the intensified LWA. The northern precipitation pattern was associated with a baroclinic trough–ridge configuration, pronounced mid‐tropospheric LWA and moisture convergence involving southwesterly transport via eastern China and southeasterly transport from the East China Sea–Yellow Sea region. In contrast, the southern precipitation pattern was related to a more equatorward and meridionally extended wave structure, enhanced lower‐tropospheric LWA and continuous southwesterly moisture transport from the subtropical oceans towards a zonally elongated precipitation band. The vertical LWA analysis revealed a bimodal structure with upper‐ and lower‐tropospheric maxima in both patterns, and the southern pattern featured more pronounced lower‐tropospheric LWA but weaker middle‐tropospheric LWA than the northern pattern.