Spatiotemporal distribution characteristics of warm season precipitation associated with Northeast China Cold Vortices

The Northeast China Cold Vortex (NCCV) is a key circulation system that drives warm-season precipitation patterns in northern China, frequently triggering local heavy rainfall and severe convection. To better understand the fine-scale structure of precipitation within NCCV systems, investigating the spatiotemporal distribution characteristics of warm-season precipitation associated with NCCVs is of great scientific significance and provides a valuable reference for forecasting. Using hourly ERA5 reanalysis product and Global multi-source merging-and-calibration precipitation dataset for the warm seasons (April to September) from 2001 to 2019, this study focuses on the mature stage of NCCVs. A dynamic, center-referenced relative coordinate composite method is employed to analyze the spatiotemporal distribution and environmental configurations of NCCV precipitation across vortices of different intensities and spatial scales. The results show that warm-season NCCV precipitation exhibits pronounced asymmetry in the relative coordinate system. Statistical results indicate that strong NCCVs are more likely to produce compact, near-center rainbands, whereas weak NCCVs tend to generate more diffuse patterns in the peripheral region. In addition, large-scale NCCVs generally correspond to broader rainbands and stronger precipitation intensity near the core area. In Northeast China, the mean precipitation rate under NCCV conditions exhibits a predominantly unimodal diurnal cycle with an afternoon maximum, whereas precipitation frequency shows peaks in the early morning and afternoon. Strong NCCVs exhibit a bimodal diurnal pattern, while weak and small-scale NCCVs shift toward a single afternoon peak pattern associated with thermal convection. Persistent heavy rainfall (PHR) events under the NCCV background exhibit an asymmetric "weak inner core, strong periphery" distribution pattern. They occur most frequently in the southeast quadrant of the NCCV, whereas the most intense precipitation events are concentrated in the southwest quadrant. Furthermore, these events are predominantly short-lived, with extreme cases (≥5 h) occurring only in the southern sectors of the vortex. Overall, different intensities and scales of NCCVs correspond to distinct precipitation distribution characteristics, indicating a close relationship between the intrinsic properties of the vortex and the spatial structure of precipitation. From the perspective of a relative coordinate system, these findings provide more refined characteristics of the spatial variability of precipitation and PHR events during the mature stage of NCCVs, offering a scientific basis for identifying high-risk precipitation areas and improving fine-scale forecasting under NCCV conditions.