Analysis of the Basic Characteristics of Extreme Rainstorms in Pingxiang City from 2009 to 2021

Li Kan; Cai Li; Gan Weijin

doi:10.16765/j.cnki.1673-7148.2025.02.007

Abstract：Based on precipitation data in Pingxiang City from 2009 to 2021 and ERA-5 reanalysis data from the European Centre for Medium-Range Weather Forecasts(ECMWF),14 extreme rainstorm events are identified by the percentile method.These events are classified into three types based on their circulation patterns,i.e.,low-trough type,typical double-high shear-type,and atypical double-high shear-type.The low-trough type extreme rainstorms are characterized by clearer impact systems,stronger south-westerly flows in low levels,and relatively good forecast performance,but they occur less frequently.The double-high shear-type extreme rainstorms occur more frequently in the warm zone of the subtropical high(or its periphery),and are more challenging to forecast.Further analysis of the low-level southwesterly jet,standardized anomalies of environmental parameters,precipitation efficiency,and duration reveals that:(1)The typical double-high shear-type events are more favorable for higher convective systems due to abnormally strong upward motion.Intense lifting conditions continuously transport abundant low-level moisture above the freezing layer,forming a deep moist layer conducive to the generation of high-efficiency precipitation and large raindrops.(2)Atypical double-high shear-type involved the intrusion of mid-level cold,and dry air overlaid on abnormally hot and humid low-level air resulted in significant convective in-stability,favoring the development of low-center,high-efficiency convective systems.The double-high shear-type extreme rainstorms have not only high precipitation efficiency,but also prolonged rainfall dura-tion.(3)Low-trough type extreme rainstorms show more pronounced dynamic lifting anomalies compared to ordinary rainstorms,but their mid-level steering flow and vertical wind shear are relatively larger,which is unfavorable for prolonged maintenance of heavy rainfall.In addition,the increase in ambient parameter values during rainfall intensification is smaller,resulting in weaker range and intensity of extreme precipi-tation relative to the double-high shear-type events.