Investigation into lightning activities in China's Three Gorges Area: LLS VS LIS between 2005 and 2008

In China's Three Gorges Area which situates in the West of Hubei Province (TGAWH), the 500kV transmission line trip-out rate caused by lightning-overvoltage reached 0.89 flashovers/100km/yr in 2009, which is above the standard issued by the State Grid Corporation of China (SGCC). The 2005-2008 statistic data from Lightning locating system (LLS) show the mean cloud-to-ground (CG) lightning density of 2.7 flashes/km
²
/yr in this area, but it reached 4 flashes/km
²
/yr around Three Gorges (TG). 70% lightning strokes of a year occurred in July and August. Lightning Image Sensor (LIS) data is also adopted in this research. The two sources of lightning observation data are compared and investigated. 391 groups of matched lightning data are identified. It is found that the mean value of the positional error distance is 11km, and the standard deviation is 0.087, demonstrating that the LIS data is in good agreement with the LLS data. An investigation was then carried out to separate the CG lighting from intercloud (IC) lightning in LIS data. The IC/CG lightning ratio is calculated and presented in the paper. The ratios were found to be greater than the values calculated from traditional flash density method. Its coefficient at average altitude is -0.33.