Abstract:
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.