Guili Feng

A Review of Atmospheric Electricity Research in China

The importance of atmospheric electricity research has been increasingly recognized in recent decades. Research on atmospheric electricity has been actively conducted since the 1980s in China. Lightning physics and its effects, as important branches of atmospheric electricity, have received more attention because of their significance both in scientific research and lightning protection applications. This paper reviews atmospheric electricity research based primarily on ground-based field experiments at different regions in China in the last decade. The results described in this review include physics and effects of lightning, rocket-triggered lightning and its physical processes of discharge, thunderstorm electricity on the Tibetan Plateau and its surrounding areas, lightning activity associated with severe convective storms, the effect and response of lightning to climate change, numerical simulation of thunderstorm electrification and lightning discharge, lightning detection and location techniques, and transient luminous events above thunderstorms.

Observation of ground potential rise caused by artificially-triggered lightning

Comparative analysis was made between the ground potential rise resulted from an artificially-triggered flash, the channel base current and close magnetic fields. The results indicated that the current peaks of the two strokes in artificially-triggered flash were 41.6 and 29.6 kA. The inferred currents, based on the close magnetic fields, were about 39.8 and 29.1 kA, in agreement with the measured ones. The ground potential rises caused by the two return strokes were about 302.8 and 141.3 kV, respectively. The downtime and half-peak width of the ground potential rise were much longer than that of the corresponding value of the channel base current. Moreover, characteristics of the ground potential rise were studied by using ATP simulation.

Characteristics of Thunderstorm Structure and Lightning Activity Causing Negative and Positive Sprites

This paper reports observation of two negative sprites and three positive sprites over a mesoscale convective system in a 15 min window. The negative sprites occurred during strong convection, indicated by the increase of the area of the thundercloud with radar echo top of 8-11, 9-11 and 6-12 km. The strong convection and large wind shear in thunderstorm middle and upper region provide favorable conditions to produce the parent cloud-to-ground (CG) lightning discharges of negative sprites. The parent CGs for the two negative sprites are likely to be hybrid intracloud-negative cloud-to-ground lightning (IC-NCG). The peak current of the parent CG of one of the negative sprites is -106.6 kA, agreeing with the values reported previously; the parent flash of the other negative sprite may be a negative CG with two return strokes with peak currents of -39.7 kA and -40.9kA, suggesting that negative sprites can also be produced by –CGs with moderate peak currents. Finally, the two negative sprites were separated by 2.66 min in time but have similar spatial features, indicating that the effects of sprites on the mesosphere may last on the order of minutes.

Return stroke current during Shandong artificially triggered lightning from 2005–2009

Shandong artificial triggering lightning experiment (SHATLE) by means of rocket-wire technique, aimed to understand the close electromagnetic environment of lightning channel and its correlation to the discharge current, was started at 2005 in Binzhou, Shandong. Artificially triggered lightning is thought to be similar to the subsequent return strokes in natural lightning. Sixty seven negative return strokes were successfully triggered from 2005 to 2009. The discharge current at the base of the discharge channel and electromagnetic fields at different distances were measured simultaneously for 25 return strokes. Although the data is not enough, the distribution of peak current of the triggered strokes shows a probability of lognormal distribution. The geometric mean value was about 11.8 kA with a minimum of 5.8 kA and a maximum of 45.7 kA. The geometric mean of the 10–90% rise time was 1.9 µs, the geometric mean of the half peak width was 22.5 µs and the geometric mean of the charge transfer within 1ms of return strokes was 0.7 C.

Current and Close Electromagnetic Fields of Artificially Triggered Lightning in Shandong, China

Shandong artificially triggering lightning experiment (SHATLE) has been continuously conducted since the summer of 2005 in Binzhou, Shandong. Eight negative lightning flashes including 32 return strokes were successfully triggered from 2005 to 2007. The discharge current and close electromagnetic fields at 50 (m) and 550 (m) distances were documented simultaneously. The whole discharge process of the triggered lightning flashes lasted from 518 (ms) to 1900 (ms). The range of current peak value for 14 recorded strokes in 3 triggered flashes was varying from 5.8 kA to 45.7 (kA) with an average value of 18.6 (kA), similar to the subsequent return strokes in natural lightning. The half peak width of the current waveform is 30.7 (¿s), which is much larger than the usual result. The peak current of stroke Ip (kA) and the neutralized Charge Q (C) has a relationship of Ip=18.5Q0.65. The radiation field of return stroke is 5.4 kV.m-1 and 0.45 (kV/m) at 60 (m) and 550 (m), respectively. The radiation field decreases as r-1.119 with increase of horizontal distance r from the discharge channel. Based on the well-accepted transmission line model, the speed of return stroke is estimated to be about 1.4×108 (m/s), with a variation range of (1.1-1.6)×108 (m/s). Because of the similarities of the triggered lightning and natural lightning, the results in this article can be used in the protection design of natural lightning.