Spatio-temporal distributions and environmental characteristics of extreme short-time heavy rainfall associated with different synoptic patterns over Northeast China

To understand the weather characteristics of extreme short-duration heavy rainfall (EHR, defined as hourly rainfall ≥50 mm) in Northeast China, this study utilizes meteorological observation station observations and ERA5 reanalysis data from 2017 to 2024. By employing a subjective synoptic typing method, EHR events are classified into five categories to comparatively analyze their spatiotemporal distributions and environmental characteristics under different synoptic patterns. The following conclusions: The frequency of EHR occurrences in Northeast China ranks from highest to lowest as: cold vortex type, the edge of the Western Pacific Subtropical High (WPSH) type, westerly trough type, typhoon type, and weak-synoptic forcing type. Compared to other EHR types, the cold vortex-type EHR exhibits stronger rainfall intensity, longer duration, and broader spatial coverage. In all provinces, the cold vortex-type EHR accounts for the highest proportion. The proportions of the WPSH and typhoon types exhibit a spatial pattern of being higher in the east than in the west, and higher in the south than in the north, whereas the weak synoptic forcing type shows the opposite pattern. The WPSH and typhoon types occur most frequently in August, and at night. while other types occur most frequently in July and in the afternoon. The cold vortex, westerly trough, and weak synoptic forcing types occur in conditions with relatively lower moisture, but are characterized by stronger static instability and more pronounced mid-level dry air. In contrast, the typhoon and WPSH types occur in warmer, moister environments with higher near-surface relative humidity, stronger low-level jets, and vertical wind shear. Compared to short-duration heavy rainfall (20–50 mm·h⁻¹), all EHR types occur in environments with higher convective available potential energy and higher near-surface relative humidity. This study preliminarily summarizes the spatiotemporal distributions and environmental parameters of EHR in Northeast China under the influence of different synoptic systems, providing a basis for improving EHR forecasting in Northeast China.