Abstract This study analyzes the microphysical characteristics of lightning initiation environments over Guangzhou, China, based on vertical radar reflectivity cores. Results indicate that the vertical reflectivity cores for both intracloud (IC) and negative cloud-to-ground (NCG) lightning initiations are concentrated within similar ranges. Approximately 88% of NCG initiations and 86% of IC initiations are associated with reflectivity cores between 35 and 60 dBZ within the 1–7 km altitude layer.Most NCG flashes initiate within a vertical range of −4–5 km around the reflectivity core, whereas IC flashes typically initiate 2–12 km above the core. While the primary initiation height of NCG flashes varies noticeably with changes in core altitude, that of IC flashes remains relatively stable.As the reflectivity core descends from higher to lower altitudes, the initiation frequency of both IC and NCG flashes first increases then decreases, peaking when the core is located at 2–3 km. However, the core altitude corresponding to peak initiation within the center and its immediate vicinity (±1 km) differs: 4–5 km for IC flashes versus 2–3 km for NCG flashes. Additionally, the NCG/IC initiation ratio generally increases as the core descends.These findings suggest that the charge layer near the reflectivity core—likely corresponding to the lower positive charge region in a tripolar structure—significantly modulates NCG lightning occurrence. The observed correlations between flash activity and core height further imply that variations in the vertical reflectivity core are synchronized with the evolution of the intracloud charge structure.

Abstract The differential reflectivity (Z DR ) column is a notable radar signature in thunderstorms, serving as a proxy for updrafts and an early indicator of storm intensity. However, a quantitative relationship among the Z DR column morphology, related microphysical characteristics, and dynamic structures based on sufficient field observations has not yet been reported. To explore these quantitative relationships, we develop a three-dimensional Z DR column identification method based on 100 Z DR columns within severe thunderstorms (primarily supercells) in the Pearl River Delta region of South China from April to July in 2021 and 2024. 3D-connected component labeling with horizontal and vertical tolerance mechanisms is integrated into the method to ensure the structural independence and integrity of multiple Z DR columns coexisting within the same thunderstorm. This method shows that Z DR columns in severe thunderstorms exhibit mean depths of approximately 2 km, mean widths of approximately 6 km, mean volumes of approximately 30 km 3 , 30–70 min lifecycles, and high liquid water contents (mean =2.23 g m −3 ). Quantitative relationships between three morphological parameters (volume, width, and depth) of Z DR columns and updraft volumes retrieved from multiradar wind fields using 1–11 m s −1 thresholds were also determined. All three morphological parameters of the Z DR column outperform the traditional 35 dBZ echo top height in indicating updraft intensity. In addition, the distribution of hydrometeors was explored. Our results, derived from extensive observations, quantitatively highlight the strong relationship between Z DR column morphology and thunderstorm dynamic structure, providing a theoretical foundation for improving severe weather warnings and forecasts.

Do systematic differences in cloud-to-ground (CG) lightning properties-particularly return stroke number and current intensity-exist across different thunderstorm types? This question is foundational not only to the atmospheric electricity but also to advancing lightning risk prediction, which crucially depends on a robust understanding of how these physical attributes vary among thunderstorm types. This study compares CG lightning characteristics between frontal (FR) and warm-sector heavy rainfall (WR) events in Guangdong, China, using data from the Guangdong Lightning Location System from 2003 to 2014. Results show that WR events feature a higher positive CG (PCG) lightning percentage, more return strokes (RSs) of negative CG (NCG) lightning, and stronger NCG lightning currents, but lower CG lightning frequency compared to FR events. FR events exhibit higher peak currents in PCG compared to NCG lightning, while WR events show the opposite pattern. These differences remain consistent across the varying precipitation intensity bins used to classify the events. Additionally, WR events develop secondary peaks in the distributions of PCG lightning percentage, NCG RS number, and NCG lightning current as precipitation intensity increases, gradually approaching the decreasing peaks in FR events at higher precipitation intensities, leading to more similar CG lightning properties between the two event types. It is demonstrated that different types of thunderstorms can produce lightning discharges with distinct physical properties. Specifically, weaker convection may correlate with more RSs and greater current in NCG lightning. This finding offers valuable insights for the construction of future lightning risk predication.

ABSTRACT This study investigates the spatiotemporal characteristics, structural features and environmental conditions of mesoscale convective systems (MCSs) over the coastal region of South China from April to June during 2013–2017, using satellite–gauge merged precipitation, cloud‐to‐ground (CG) lightning data, radar observations and reanalysis data. All analysed MCSs generate rainfall and are classified into two categories based on lightning activity: rainfall‐only MCSs (without observed CG lightning) and lightning‐producing MCSs (rainfall with CG lightning). Their spatial structures, rainfall and lightning behaviours and associated circulation patterns are compared, with emphasis on variations before and after monsoon onset. Results show that lightning‐producing MCSs are generally larger in both horizontal and vertical extent than rainfall‐only MCSs, especially after monsoon onset, when both types become more vertically developed. Before monsoon onset, lightning‐producing MCSs are less frequent but produce stronger rainfall. After monsoon onset, their frequency increases while rainfall intensity weakens. In contrast, rainfall‐only MCSs show increases in both frequency and rainfall intensity after monsoon onset. The formation of lightning hotspots is influenced by both the frequency of lightning‐producing MCS occurrences and their internal lightning intensity, with the latter playing a more dominant role. Circulation types favourable for MCS development differ significantly. Lightning‐producing MCSs tend to occur along the western flank of the subtropical high under southwesterly low‐level winds, with convective instability peaking in the afternoon. Rainfall‐only MCSs are more common within the subtropical high under southeasterly flows, where nocturnal convergence and orographic lifting promote their development. These circulation differences are shaped by seasonal variations in moisture, thermodynamics and topography. This study provides a comprehensive understanding of MCS‐related rainfall and lightning, offering insights for forecasting and model evaluation.

Weather Foundation Models (WFMs) have recently attracted significant attention for their exceptional performance and inference efficiency in global-scale weather forecasting. However, their coarse spatial resolution and inherent biases constrain their utility for station-level forecasting, which is crucial for applications such as renewable energy management and aviation safety. To address these limitations, we propose the Adaptive Spatiotemporal Alignment Fusion Network (ASTAFN), a novel framework designed for accurate station-level weather forecasting through the synergistic integration of WFMs and station observations. ASTAFN incorporates two complementary data sources: (1) recent station observations, which offer fine-grained local trend information, and (2) WFM-generated forecasts, which provide broad-scale weather patterns. The core innovation of ASTAFN lies in its proxy station learning mechanism, which aligns the spatial structure and corrects the biases of WFMs relative to actual station data, facilitating the extraction of homogeneous spatiotemporal features from both sources. These features are dynamically fused at each forecasting step using an adaptive strategy, effectively compensating for WFM biases and enhancing predictive accuracy. Experimental evaluations on three real-world datasets demonstrate that ASTAFN reduces mean absolute error by 20%-35% compared to baseline WFMs for station-level wind speed forecasting. ASTAFN has been deployed on the regional station-level weather forecasting and analysis platform of the Chinese Academy of Meteorological Sciences, currently serving the Guangdong and Yunnan provinces in southern China.

This study utilized the Thunderstorm Feature Dataset (TFD), combined with the sea surface temperature (SST) anomalies over the NINO3.4 region (ENSO index) from the NOAA/ERSSTv5 dataset and ERA5 reanalysis data, to investigate the response of thunderstorm activity in East Asia and the Western Pacific region to ENSO events, an aspect that has been seldom addressed in previous studies. Results indicate ENSO events as the primary factors influencing the interannual variation of thunderstorm activity in the study area, with thunderstorm activity anomalies negatively correlated with the ENSO index, lagging by approximately 3 months. Regionally, thunderstorm activity anomalies and the ENSO index show a strong positive correlation in areas north of 20 degrees N, encompassing Southeastern China land and adjacent sea area, but a negative correlation in areas south of 20 degrees N, including the South China Sea, the Philippine Islands, and parts of the Western Pacific. Thunderstorm activity anomalies in these areas all lag the ENSO index by 1-3 months. The response of thunderstorm activity to ENSO events demonstrates a strong correlation with anomalies in convective parameters such as convective available potential energy (CAPE), K index, the mid-level (700-400 hPa) averaged relative humidity, and 500 hPa vertical velocity. During El Nino, warm SST in the central and eastern equatorial Pacific, along with enhanced upward motion, leads to anomalous downward motion and anticyclonic circulation in the Western Pacific region within the study area, resulting in a decrease in thunderstorm activity. Concurrently, the anomalous anticyclonic circulation in the Western Pacific region enhances the warm, moist southwest winds, which transport more water vapor to Southeastern China, thereby increasing thunderstorm activity. Conversely, during La Nina, the anomalous cyclonic circulation and moisture convergence in the Western Pacific region result in an increase in thunderstorm activity in the Western Pacific region within the study area. Additionally, the anomalous cyclonic circulation leads to a weakening of the warm and moist southwest winds and upward motion in the Southeastern China land area, consequently reducing thunderstorm activity.

This study analyzes 53 storms that occurred in the summer of 2015, using data from the Guangdong-Hong Kong-Macao Lightning Location System (GLLS) and an S-band Doppler radar observation. Among these storms, 34 produced large-peak-current cloud-to-ground (LCG) lightning, 10 produced only small-peak-current CG (SCG) lightning, and 9 produced no detectable CG lightning. The results show that the combination of 40 dBZ echo top height (Top40) and 40 dBZ echo area at 5 km altitude (Area40_5) effectively distinguishes LCG-dominant storms from non-LCG storms. The analysis reveals that updraft intensity fundamentally controls LCG production. Storms exhibiting maximum Top40 >= 12 km show evidently higher peak LCG frequencies and greater total LCG counts compared to storms with weaker updrafts. Notably, even storms with maximum Top40 < 12 km can achieve substantial LCG production when these moderately intense updrafts exhibit prolonged duration. A robust correlation emerges between the maximum Top40 values recorded during the 30-min period preceding LCG initiation and subsequent LCG counts in the initial active phase. Throughout storm lifetimes, Top40 variations mirror LCG frequency trends, with Top40 and Area40_5 values during LCG-active periods consistently exceeding those during SCG-only periods. Primary LCG activity predominantly occurs during Area40_5's growth phase prior to peak development, followed by rapid weakening or diminishment after the peak. These findings confirm that LCGs result from active updrafts, which may provide both favorable conditions for vigorous electrification and formation of high-density charge structures. Consequently, frequent LCG activity serves as an indicator of active updraft periods in storms. It should be noted that the thunderstorm cases analyzed in this study were all from a single summer season. Although the fundamental trends and relationships identified are expected to be robust, some specific quantitative values may vary interannually. Furthermore, the analysis primarily focused on localized, small-scale thunderstorms, which represent the most common type during the local summer. Consequently, the conclusions drawn here may not be fully applicable to larger-scale convective systems and should be interpreted with caution in such contexts.

We reported on the nighttime observations of totally 20 transient luminous events (TLEs), including ten produced by negative cloud-to-ground (CG) strokes, over a coastal thunderstorm in South China on August 28, 2021. The lightning activity in this thunderstorm exhibited typical characteristics for coastal thunderstorms, with intense negative single-stroke flashes accounting for 76 % of all flashes with peak current exceeding -200 kA. Remarkably, most of the negative CG flashes related to TLE observations spawned only one negative CG stroke with high peak current (typically > -100 kA). Moreover, the outbreak of TLEs with elves and halo features requiring high peak current is likely linked to the intensification of convection in the thunderstorm, which occurred while the thunderstorm approached the coastline from the open sea, followed by a substantial growth in the cloud-top height and radar reflectivity. On the other hand, red sprites produced by positive CG strokes were observed almost throughout the observation period, with peak currents (averaging at +63 kA) much smaller than that of negative sprite-producing CG strokes. Overall, the TLE observations over this particular thunderstorm provide more insights into the TLE phenomenology of oceanic thunderstorms, and our analyses contribute to a better understanding on how oceanic thunderstorms affect the middle and upper atmosphere by producing intense negative CG strokes.

This study analyzes the relationship of spatiotemporal configuration between lightning activities and ZDR and KDP columns during two squall lines over Guangzhou on 4 and 8 May 2017.The observations are from a S-band dual-polarization radar and the Low-Frequency Electric Field Detection Array.The results show that:(1)During the early stage of lightning activities(the intracloud(IC)lightning frequency is less than 50/(6 min),and the cloud-to-ground(CG)lightning frequency is less than 10/(6 min)),IC lightning and CG lightning mainly occurred within the plane spatial coverage of ZDR and KDP columns,and IC lightning tended to occur within the area of KDP columns(the maximum percentage can exceed 40%).As lightning activities became more active,IC lightning and CG lightning activities mainly occurred outside the planar coverage of the ZDR and KDP columns.(2)Changes in ZDR and KDP column volume led the trend of the IC lightning and CG lightning activity by about 30 min,and the correlation coefficient approached or exceeded 0.9.In addition,the peak of ZDR column volume was a good predictor of the occurrence of IC lightning and CG lightning peak.The results of this study have important scientific significance for understanding the relationship between lightning activities and the dynamic structure of the complex mesoscale weather systems.It also provides new perspectives for early warning and forecasting of lightning activities via dual-polarization weather radar data.

Although the disparities in lightning activity between continental and oceanic thunderstorms have been widely investigated from thermodynamic, dynamic, and aerosol perspectives, their hydrometeor characteristics remain inadequately understood. This study compares microphysical properties of total thunderstorms and lightning-bearing cloud columns (lightning columns) over continental South China (SC) and oceanic South China Sea (SCS) using the observations from the Dual-frequency Precipitation Radar onboard the Global Precipitation Measurement satellite and lightning data from the Earth Networks Total Lightning Network and World Wide Lightning Location Network. Results show that SC thunderstorms feature higher echo tops of strong echoes (>= 40 dBZ) than SCS thunderstorms, while SCS thunderstorms are spatially about three times as large as SC thunderstorms. SC thunderstorms have higher volume fractions of low-density ice particles across all sizes and of larger-sized dense ice and mixed-phase particles, whereas SCS thunderstorms exhibit higher fractions of small-to-medium-sized dense ice/mixed-phase particles and liquid water. Lightning columns in both regions contain more abundant and larger hydrometeors than overall thunderstorms, and the regional differences in hydrometeor properties between lightning columns are broadly consistent with those between the thunderstorms. Differences in volume-weighted mean diameter are most pronounced within the mixed-phase zone (0 to -20 degrees C).

This study develops a novel framework within the Weather Research and Forecast Model for modeling aerosol-cloud-lightning interactions. The framework explicitly represents aerosol-cloud interactions by prescribing aerosols with two configurations: an idealized setup, where both cloud condensation nuclei (CCN) and ice nucleating particles (IN) are assumed to have a single chemical composition and spatially uniform distributions; and a quasi-realistic configuration, with multi-species aerosols assigned spatially varying distributions, where hygroscopic components act as CCN, dust particles act as IN, and all aerosol species influence radiative transfer. Cloud microphysics is coupled with detailed charge separation and discharge processes to enable the lightning simulation. The framework is evaluated using two thunderstorms in Guangdong, China. For an isolated storm, the model successfully reproduces the observed tripolar charge structure (positive-negative-positive), demonstrating its capability in simulating cloud electrification. For a frontal storm, it captures well the observed precipitation and lightning, and shows that increasing CCN suppresses the rainfall while enhancing the lightning. Higher CCN concentrations produce more numerous but smaller cloud droplets, which suppresses the coalescence into rain droplets, allows a greater number of droplets to loft into the upper troposphere, and forms more but smaller cloud ice particles. This boosts graupel-ice collisions, intensifies non-inductive charging, strengthens the upper positive charge and the vertical electric-field gradient, ultimately increasing the lightning frequency. In contrast, no significant aerosol-induced invigoration of updrafts is observed. These results highlight the dominant role of aerosol microphysical effects over dynamical invigoration in modulating thunderstorm electrification and lightning activity.

Since its establishment, Chinese Academy of Meteorological Sciences (CAMS) has conducted long-term and continuous research on lightning. Systematic progress has been achieved in the construction of lightning research platforms, the development and application of lightning detection and locating technologies, artificially triggered lightning experiments and lightning protection testing, lightning observation and research on tall structures, studies on thunderstorm lightning activity, and the development and application of forecasting and nowcasting methods:CAMS has established two ministerial-level innovation platforms-the Field Scientific Experiment Base and the Key Open Laboratory of China Meteorological Administration for Lightning Research. Internationally recognized facilities, such as the Guangzhou Experiment Site for Triggered Lightning and Testing, and the Tall-Object Lightning Observatory in Guangzhou (TOLOG), have also been constructed.A variety of technical instruments have been independently developed, such as the low-frequency three-dimensional total lightning detection array, the very-high-frequency (VHF) broadband lightning interferometer, and the lightning channel optical imager. The multi-parameter synchronous observation of lightning have been conducted, and high-quality observational data for scientific research and operational services have been obtained.The lightning strike mechanism and protection testing platform has been established, and artificially triggered lightning experiments are carried out. Lightning striking tests have been performed on various objects, including weather stations, communication base stations, high-voltage transmission lines, wind turbines, and oil tanks. The largest dataset for artificially triggered lightning experiments and the protection tests under real lightning conditions in China has been established, and relevant results have promoted the development of lightning protection technology across multiple industries.A distinctive, high-quality dataset featuring lightning on tall objects of varying heights and top shapes has been established, yielding new insights into connection behavior between different types of leaders, striking distance, and channel spectral characteristics.The lightning research at CAMS has clarified the spatiotemporal distribution of lightning activity, polarity ratios, and their correlation with charge structures in mesoscale convective systems, severe thunderstorms, and tropical cyclones, explaining the mechanisms behind variations in lightning frequency and scale from both dynamic and microphysical perspectives.By integrating artificial intelligence technologies, an integrated lightning nowcasting and short-term forecasting system has been developed. This system has been implemented in meteorological departments across multiple provinces and municipalities and provides specialized meteorological services for various industries.

At present, China's meteorological departments are gradually upgrading their lightning location networks from ADTD (Advanced TOA and Direction) system to DDW1 Total Lightning Location System. Based on lightning data from both DDW1 and ADTD in Jiangsu Province, the spatiotemporal distribution characteristics and current intensity of lightning events are comparatively analyzed to evaluate consistency and differences in detection performance between these two systems. Based on this comparison, the evolution of total lightning activity and the vertical distribution of cloud flashes during a squall line event on 4 July 2024 are examined through integrated analysis of S-band weather radar observations and Jiangsu Atmospheric Sounding Array (JASA) data, elucidating capabilities and constraints of DDW1 in detecting total lightning during severe convective weather. Results indicate that DDW1 and ADTD show consistent spatiotemporal patterns of cloud-to-ground (CG) lightning activity, both exhibiting a clear decreasing trend from south to north, with summer being the dominant season for CG lightning occurrence. Despite this similarity, DDW1 detects higher average density of CG lightning (especially positive CG lightning) with more spatially concentrated high-density regions compared to ADTD. The diurnal variation shows that CG lightning activity begins to increase at around 1000 BT in both systems, DDW1 exhibits a single-peak pattern in the afternoon, while ADTD displays a multi-peak distribution. Regarding current intensity, DDW1 generally reports lower current values than ADTD. It also detects low-magnitude currents (0-5 kA) over an area approximately 15 times larger than ADTD, indicating significantly higher sensitivity to weak lightning discharges. During the analyzed squall line event, lightning detected by DDW1 predominantly clustered within areas exhibiting strong radar reflectivity (exceeding 35 dBZ), with cloud flashes reaching maximum frequency at altitude between 9 and 11 km. Spatial and vertical variations of lightning activity correspond well with the evolution of intense radar echoes, while temporal variation in total flash frequency shows excellent agreement with JASA observations. These results confirm the operational reliability of DDW1 for total lightning monitoring during severe weather events. Although DDW1 shows notable advantages in lightning monitoring through enhanced detection sensitivity and expanded spatial coverage, its classification algorithms and cloud flash detection capabilities need further improvements.

Lightning field experiment is an indispensable research methodology for scientifically understanding characteristics of lightning occurrence and physical processes, exploring the lightning disaster-causing mechanisms, and evaluating protection techniques for different objects under actual lightning strike conditions. Since 2006, Chinese Academy of Meteorological Sciences and Guangzhou Institute of Tropical and Marine Meteorology, China Meteorological Administration (CMA) have been conducting the Guangdong Comprehensive Observing Experiment on Lightning Discharge (GCOELD) for 20 consecutive years. The Field Experiment Base on Lightning Sciences, CMA (CMA_FEBLS), is established, forming a comprehensive experimental platform integrating multiple functions such as artificially triggered lightning experiments, lightning protection technique tests, fine detection, and tall-object lightning observation.249 flashes have been successfully triggered, and lightning strike tests have been carried out on various objects including automatic weather stations, telecommunication base stations, high-voltage transmission lines, wind turbines, and petroleum storage facilities. A dataset of lightning induction and protection tests has been established, providing key scientific data for in-depth research on lightning physical processes, understanding lightning disasters, and improving lightning protection technique.Multi-band lightning locating techniques have been developed, which feature real-time and efficient locating capabilities for discharge activities of thunderstorms, as well as precise positioning capabilities for lightning channels. Through integrated analysis of precisely mapped lightning channels (both triggered and natural lightning), synchronized measurements of current, electromagnetic fields, and optical recordings, new insights have been gained into aspects such as the initiation and evolution mechanisms of lightning, the development and propagation of leaders, return strokes, and M-component discharges.Additionally, the Tall-object Lightning Observatory in Guangzhou (TOLOG) has been established, accumulating a high-quality dataset of over 600 flashes occurring on super-tall buildings. The connecting behavior between the tip of negative leader and the lateral surface of positive leader during the attachment process was revealed for the first time, and two basic leader connection scenarios are inferred. Furthermore, quantitative data on characteristics such as the initial height, length and velocity of the upward leader initialed from structures of varying heights have been systematically obtained.

Abstract. Cloud microphysics and dynamics produce lightning flashes, which can be detected as polarimetric structures by radar. Many studies have indicated that differential reflectivity (ZDR) and specific differential phase (KDP) columns, which serve as proxies for updraft strength, are related to lightning activity; moreover, the quantities of ice and supercooled liquid water strongly influence the occurrence of lightning flashes via noninductive charging. However, few studies have focused on clarifying the sequence or interactions among these factors from the perspective of the cloud life cycle. Here, we establish the ‘3D mapping columns’ method, which is based on the Cartesian grid datasets; this method is sensitive for identifying and quantifying the ZDR columns in the early phase of cloud formation. Our study bridges the polarimetric structure and lightning activity within an isolated thunderstorm during the cloud life cycle. The results indicate that i) the parameter most relevant to total flashes/cloud-to-ground flashes is the content of supercooled rainwater/graupel. ii) The onset of the ZDR column can be used to forecast lightning initiation in advance. iii) The signatures of the ZDR and KDP columns should be complementary and used to retrieve dynamic information instead of lightning activity. Notably, the variation in the ZH intensity within ZDR columns has high potential for predicting lightning activity during the cloud life cycle, which is valuable for exploration in the future. Our study improves the overall understanding of cloud microphysics and lightning activity, and suggestions for using these multiple polarimetric signatures to forecast severe weather are provided.

Using lightning data from the Lightning Imaging Sensor onboard the Tropical Rainfall Measurement Mission satellite, together with cloud and precipitation property data extracted from the Radar Precipitation Feature dataset, this study investigated the statistical characteristics of thunderstorm structure and lightning properties over land (South China) and the South China Sea (SCS) during 1998–2014. The objective was to compare thunderstorm structural differences and explore the impact of thunderstorm structure on lightning properties between land and transitional water areas to the deep ocean. The results indicate that the lightning activity in South China is notably more intense than that over the SCS, with the average frequency and density of lightning in South China approximately doubling the values of those over the SCS. Although the mean flash duration is similar in both regions, lightning over the SCS exhibits larger average values for flash length, footprint, and radiance. Additionally, the horizontal scale and the vertical extension of thunderstorms over the SCS are substantially larger than those in South China, i.e., the thunderstorm precipitation area and the 20-dBZ area over the SCS are twice the size of those in South China, and the average 20-dBZ echo top height is 1.25 km higher over the SCS. Nevertheless, thunderstorms in South China develop more intensely, with elevated heights of the intense convective core (40-dBZ echo) compared with those thunderstorms over the SCS. The mean values of the 37-GHz minimum polarization-corrected temperature (PCT) are comparable between the two regions, but the mean value of the 85-GHz PCT is lower over the SCS, suggesting a higher concentration of small ice particles in SCS thunderstorms. Finally, a conceptual diagram that highlights the differences in thunderstorm structure and lightning flash properties between South China and the SCS is proposed. Compared with previous studies, this study has elucidated the distinct characteristics of oceanic lightning over the SCS, and highlighted the gradual transition of thunderstorm scale and lightning properties from land, to the SCS, and finally to the deep ocean area of the Northwest Pacific Ocean.

Polarimetric structures detected by radar can characterize cloud microphysics and dynamics. Many studies have indicated that differential reflectivity (ZDR) and specific differential phase (KDP) columns, which serve as proxies for updraught strength, are related to lightning activity; moreover, the quantities of ice and supercooled liquid water strongly influence the occurrence of lightning flashes via non-inductive charging. However, the sequence or interactions among these factors with dynamics and microphysics from the perspective of the cloud life cycle are uncertain. Here, we improve the “3D mapping columns” method to identify and quantify the ZDR/KDP columns, which is based on Cartesian grid datasets; this method is sensitive in the early phase of cloud formation. Our study bridges the polarimetric structure and lightning activity within 15 isolated thunderstorms during the cloud life cycle. The results indicate that microphysical variations in supercooled liquid water and graupel yield better correlation coefficients for the lightning activity prediction at short warning times (e.g. 6 min) than dynamical variations in the ZDR column volume do; however, the trend of the ZDR column volume implies good performance at longer warning times (e.g. 12 min). The KDP column is probably absent in the early phase of convection development; however, it will occur in the later stage with heavily cold cloud processes, replacing the ZDR column to indicate updraughts within the reflectivity core when obvious graupels and hailstones occur. Our study improves the understanding of the polarimetric structure, which is related to dynamics and microphysics, and is also associated with lightning activity.

Lightning discharge between the thundercloud and the sea surface is a gas-liquid interface discharge, accompanied by intense electromagnetic radiation, causing severe interference to underwater electromagnetic equipment. Elucidating the electromagnetic radiation characteristics during lighting discharge has practical significance for optimizing the anti-interference capacity of underwater electromagnetic equipment. In this paper, a liquid interface pulsed discharge system was constructed, simulating the lightning discharge on seawater through the application of a kA-level pulse current. The electromagnetic radiation signals (within 200 MHz band), electrical parameters, and the space-time evolution of plasma during the discharge process were obtained through a combined diagnosis system, and the time and frequency domain analysis was carried out. The results indicate that the electromagnetic radiation during the interface discharge correspond to three stages: (I) application of pulse current, (II) partial discharge, (III) plasma development. Under different solution conductivities and different diameters of the induction wire, the electromagnetic radiation has stable spectral characteristics, showing distinct stripe regions, located around 115 MHz, 128 MHz, and 145 MHz, respectively. Such characteristic spectrum is of great significance for further research and applications.

Due to the limited coverage of three-dimensional lightning detection networks,research on the total lightning characteristics of supercells that produce tornadoes and hail remains insufficient in China.A su-percell generating a severe tornado and hailstones exceeding 10 cm in diameter in Guangdong Province on 27 April 2024 is analyzed,utilizing dual-polarization radar data,Guangdong-Hong Kong-Macao Lightning Location Data,and three-dimensional lightning mapping data from the low-frequency E-field detection ar-ray(LFEDA).Results indicate that the mesocyclone within the supercell persists for 4.5 h,with 16067 total lightning flashes and a peak flash rate of 610 flashes per 6 min.Intra-cloud flashes account for the majority of lightning activity(92.30％),and there are significant positive correlations between fluctua-tions in graupel volume above the melting layer and total lightning flash rates(r=0.85,p＜0.05).Prior to the formation of a tornado,rapid reductions in mesocyclone height and horizontal scale are observed,ac-companied by an increased proportion of positive cloud-to-ground lightning flashes(51.73％).The lower boundary of the high-density lightning radiation source region(no less than 60 km-1·(6 min)-1)de-scends from 4.2 km to 2.0 km.During the tornadic phase,the lightning hole(a region characterized by minimal lightning initiation or propagation)emerges simultaneously with the tornado touchdown and cor-responds to the area of strong updraft.The lightning-active zone(defined as lightning extent density no less than 20 km-2)is located north of the lightning hole.Post-tornadogenesis,total lightning activity in-tensifies significantly,with higher peak flash rates and an upward shift of approximately 1 km in the upper boundary of the high-density lightning source region,while the proportion of cloud-to-ground lightning de-creased.Microphysical analysis reveals that the vertically integrated liquid water content experiences a rap-id increase,with a 126-min interval observed between this increase and the initial occurrence of hail hitting the ground.The average height of initial lightning radiation sources is 9.42 km,which corresponds to a temperature of-25 ℃ level.During hail events,the spatial distribution of the flash convex hull area and lightning extent density is relatively low within the hail accumulation zone at-25 ℃ level.The hail core is situated to the south of the lightning-active zone,whereas the hail impact locations are found on the west side of this lightning-active zone.