Return stroke currents of triggered lightning in Guangdong, China

The current measurements of 17 return strokes (RSs) produced by 6 classical triggered lightning flashes (TLFs) conducted in Guangdong, China from 2008 to 2010 were analyzed for the first time in this study. The geometric mean (GM) value of the peak value current (I_Peak) is 16.59 kA, the half-peak width (t_HPW) is 21.91 μs, the 10-90% risetime (t_10-90%) is 0.45 μs, the 10-90% average gradient (G_10-90%) is 29.61 kA μs^-1, the maximum gradient (G_Max) is 55.89 kA μs^-1, the charge transfer in 1ms after the beginning of the return strokes (Q_1ms) is 1.61 C, and the action integral in 1ms after the beginning of the return strokes (AI_1ms) is 6.60×10³ A² s. The RSs in GCOELD are, on average, stronger than those reported by other authors referenced in this study. The peak value current has a general good linear relation with G_10-90% (determination coefficient (R²) = 0.64), a good linear relation with G_Max (R²=0.74), a strong power function relation with Q_1ms (R²=0.89), and an excellent logarithmic function relation with AI_1ms (R²=0.92). Additionally, the current of the initial-stage return stroke (ISRS) of an altitude TLF was analyzed and found to have small t_HPW (2.12 μs), charge transfer (36.37 mC) and action integral (181.56 A² s), but was similar to other RSs for all other parameters. After the ISRS, a number of chopped-shape pulses, attributed to the back-and-forth reflections of the ISRS current, were recorded and analyzed for their characteristics.