Abstract:Lightning activity is closely associated with deep convective systems and serves as an effective indicator of convective intensity.Understanding the relationship between lightning and precipitation is essential for improving severe weather forecasting.However,this relationship is complex,particularly due to the pronounced variability in lightning activity under heavy rainfall conditions.Atmospheric moisture and temperature stratification are two key factors controlling atmospheric instability,and their vertical structures play critical roles in thunderstorm electrification and discharge processes.This study therefore investigates the synergistic relationship between lightning activity and atmospheric profiles during heavy rainfall events,with the aim of improving forecasting and early warning capabilities for heavy precipitation and lightning hazards.
This study first examines the regional characteristics of heavy precipitation and lightning activity in inland southern China.The K-means clustering method is then applied to identify relationships between lightning activity and atmospheric profile characteristics during heavy rainfall events.Finally,multiple linear regression is used to assess the sensitivity of lightning activity to different atmospheric stratification factors.The results reveal clear regional differences in heavy precipitation characteristics.The northwestern (100°—105°E,25°—30°N) and southwestern (100°—105°E,22.5°—27.5°N) regions are characterized by heavy rainfall events with relatively small spatial extent but high precipitation intensity.Incontrast,the northeastern (105°—115°E,25°—30°N) and southeastern (105°—115°E,22.5°—27.5°N) regions exhibit events with broader spatial coverage but lower intensity.
A common feature across all four regions is that heavy rainfall events are generally associated with relatively low lightning flash rates.Nevertheless,lightning activity during these events is strongly correlated with the vertical thermal and moisture structure of the atmosphere.Under conditions of frequent lightning,the relative humidity profile shows a pronounced vertical gradient,with high humidity in the lower troposphere (below 850 hPa) and significantly lower humidity in the mid-to-upper troposphere (500—400 hPa).In addition,cloud liquid water content is high and concentrated near 800 hPa,while cloud ice water content exhibits a pronounced peak near 200 hPa.Incontrast,when lightning activity is weak,lower-tropospheric humidity is reduced and shows less contrast with mid-level humidity,cloud liquid water content is lower and more vertically uniform,and the peak of cloud ice content occurs at lower altitudes.
The sensitivity of lightning flash rates to atmospheric thermodynamic parameters also exhibits regional dependence.In the northwestern and southwestern regions,lightning activity is primarily controlled by lower-tropospheric relative humidity (1 000—800 hPa).In the northeastern region,the mean temperature between 1 000 and 200 hPa plays a dominant role.In the southeastern region,the lapse rate of relative humidity in the mid-to-upper troposphere (500—400 hPa) shows the strongest correlation with lightning activity.
Overall,this study systematically elucidates the relationship between lightning activity and the vertical thermal-moisture structure of the atmosphere during heavy rainfall events in inland southern China.The results highlight the diagnostic value of atmospheric profiles for lightning activity and provide a scientific basis for improving severe weather forecasting and early warning.Future research will extend this analysis to all-weather conditions to further clarify the response of lightning activity to atmospheric thermodynamic structures,thereby enhancing predictive capabilities for meteorological hazards.
