应用气象学报 (Mar 2021)
Comparison of the Performance of Different Lightning Jump Algorithms in Beijing
Abstract
Based on S-band Doppler weather radar raw data, the total lightning location data of Beijing Lightning Network (BLNET) and hailfall reports from Beijing Meteorological Service, two lightning jump algorithms, Gatlin algorithm and σ algorithm, with different configurations are compared and analyzed for early warning performance of 177 hailfall events in Beijing from 2015 to 2018. The results show that, the early warnings of different multiples of σ algorithm are quite different, 2σ (in this situation, the current changing rate of total flash exceeds two times of the standard deviation of total flash rate in previous time) has the best performance in the σ algorithm. That is to say, 2σ algorithm has the highest probability of detection (POD) and critical success index (CSI), as well as the lowest false alarm rate (FAR), comparing with σ, 3σ and 4σ algorithms. The early warnings of Gatlin algorithm under different N (which is the amount of samples before current time used to calculate the mean and standard deviation) configurations have little difference, and the early warning efficiency is best when N=6, comparing with N=7, 8, 9 and 10. The POD, FAR and CSI of 2σ algorithm are 80.2%, 41.6%, and 51.1%, respectively. The corresponding results of the Gatlin algorithm with N=6 are 82.5%, 62.0%, and 35.2%, respectively. In addition, the applications of these two algorithms to a multi-cell thunderstorm process and a squall line process are analyzed in detail. The results also show that Gatlin algorithm with N=6 has a slightly higher POD than 2σ algorithm, but its FAR is much higher and its CSI is lower. Considering the evaluation of hail nowcast results by Gatlin algorithm and 2σ algorithm, 2σ lightning jump algorithm is more suitable for hail nowcasting in Beijing. And it is beneficial to improving the application of lightning data to hail nowcasting in Beijing
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