Role of the Northeast China Cold Vortex in Early-Summer Precipitation over Central and Northeast China

The Northeast China Cold Vortex (NCCV) is particularly frequent in early-summer and has a significant impact on rainbands over Central–Eastern China; However, its regional mechanistic pathways remain poorly understood. This study investigated the NCCV’s influence and associated mechanisms on rainbands from May to June between 1961 and 2023, using CN05.1 precipitation and ERA5 reanalysis dataset. K-means clustering identified five distinct precipitation patterns during NCCV days: Northeast China (NEC), northern China, the Yangtze-Huai River, south of the Yangtze River (SYR), and South China. Among these, the NEC and SYR clusters were most strongly affected by the NCCV. The presence of the NCCV was linked to a large amplitude Rossby wave over Eurasia, with a dominant dipole blocking pattern over northeastern Asia. Coupled with a farther westward extension of the western Pacific subtropical high, the NCCV enhanced northward transport of warm, moist air and ascent over the NEC and SYR regions. Quasi-geostrophic omega inversion revealed that ascent was mainly driven by the mean-flow transport of NCCV cyclonic vorticity anomalies and warm advection by southwesterly wind anomalies intensified by the NCCV. Considering the NEC cluster, easterly anomalies further conveyed positive vorticity and warm anomalies westward, inducing localized ascent along the leeside Greater Khingan Mountains. In contrast, the SYR cluster was associated with more southeastward-displaced NCCVs, where westerly anomalies along their southwestern flank intensified warm advection, promoting vertical ascent. These findings highlight the dynamic and thermodynamic roles of the NCCV in enhancing early-summer rainfall variability over Central–Eastern China.