Abstract:To enhance the forecasting capability for flash heavy rainfall (FHR) in the Beijing Daxing International Airport (PKX) region, by using minutely and hourly data from May to September during 2014-2023, combined with ERA5 reanalysis data, this paper classifies circulation patterns and analyzes the precipitation as well as their spatio temporal distribution characteristics and ambient conditions. The results show that FHR processes are classified into five circulation patterns, listing in descending order according to their percentages as follows: the Mongolian vortex and trough type, the western Pacific subtropical high edge type, the interaction type of westerly trough and western Pacific subtropical high, the Huang Huai vortex inverted trough type, and the Northeast China cold vortex rear type. The annual average frequency of FHR is relatively higher in the eastern part of the PKX region, showing an upward fluctuating trend over the past decade. FHR events are most frequent in July and August, with that in July accounting for more than half of the occurrences. The diurnal variation exhibits a unimodal distribution, peaking in the period from 22:00 BT to 23:00 BT, with durations generally ranging from 40 to 80 min. The western Pacific subtropical high edge type, the interaction type of westerly trough and western Pacific subtropical high, and the Northeast China cold vortex rear type have distinct temporal characteristics, with the former two being predominantly nocturnal and the latter occurring more frequently in the afternoon. Intense FHR (≥50 mm·h-1) primarily occurs under western Pacific subtropical high edge type, and Mongolian vortex and trough type. Significant differences are observed in the ambient conditions under different circulation patterns. The western Pacific subtropical high edge type, interaction type of westerly trough and western Pacific subtropical high, and the Huang Huai vortex inverted trough type are characterized by abundant moisture, with the vertically integrated precipitable water exceeding 50 mm and high convective available potential energy, whereas the Huang Huai vortex inverted trough type exhibits strong moisture convergence despite weaker thermal instability, often featuring boundary layer easterly jets that sustain precipitation. The Northeast China cold vortex rear type, despite limited integrated moisture, is benefitial for localized heavy rainfall through strong low level warm advection and significant upper lower atmospheric temperature differences, favoring the development of localized heavy rainfall.