Comparative Analysis of Radar Characteristics of Lightning Activity in Eastern and Western China
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Abstract:
Lightning, as one of the frequent natural disasters in China, poses significant meteorological hazards. Weather radar systems, with their inherent advantages of high spatiotemporal resolution, enable precise characterisation of lightning formation mechanisms and evolutionary patterns through synergistic integration with lightning detection datasets. This paper analyses lightning forecasting and early warning services in the eastern and western regions of China, using Shanghai and Kashgar as representatives. By leveraging multi-source observations, including lightning locators, weather radar mosaic products, and sounding data, an annual statistical analysis of the spatiotemporal distribution, three-dimensional characteristics of lightning, and their corresponding radar signatures is conducted in these two regions. The study explores the causes of the differences in lightning characteristics between the eastern and western regions. The results indicate that: (1) Both Shanghai and Kashgar exhibit concentrated lightning activity between May and September, with peak occurrences from afternoon to evening. Notably, Kashgar demonstrates distinct nocturnal characteristics in lightning distribution due to topographic effects. Geospatial analysis reveals contrasting spatial patterns: Shanghai’s lightning hotspots predominantly cluster over urbanised areas and land-water interfaces, whereas Kashgar’s lightning distribution shows strong orographic correlation, with maximum density zones located along the southern foothills of the Western Tianshan Mountains, eastern flanks of the Pamir Plateau, and northern slopes of the Kunlun Mountains. Statistically, the average lightning stroke density in Shanghai significantly surpasses that in Kashgar, maintaining a ratio of approximately 732.1∶1. (2) The combined reflectivity factor intensity, echo top height, and vertical liquid water content associated with lightning echo cells in Shanghai are markedly greater than those observed in Kashgar. The extension height of lightning echo cells in Shanghai is substantially higher than that in Kashgar. Notably, the 30 dBz, 35 dBz, and 40 dBz echo exceeding the -20 ℃, -10 ℃, and 0 ℃ layer height serves as a crucial indicator for lightning forecasting and early warning in Shanghai, whereas for Kashgar, the echo top height surpassing the -10 ℃ layer and the 30 dBz echo reaching the 0 ℃ layer hold greater predictive value. (3) Lightning activity is formed under the combined effects of three essential factors: sufficient atmospheric instability energy, dynamic lifting mechanisms, and adequate moisture supply. Comparative analysis reveals that during thunderstorm days, Shanghai exhibits significantly higher values of Most Unstable CAPE (MUCAPE), mid-level Relative Humidity (midRH), and Precipitable Water (PW) compared to Kashgar, while demonstrating lower Most Unstable Lifted Index (MULI) values. These meteorological parameters indicate stronger convective activity in Shanghai, where intense updrafts transport abundant moisture to upper colder layers. This enhanced vertical transport mechanism creates more favourable conditions for charge separation processes, making Shanghai more prone to lightning activity than Kashgar.