Observation on Upward Lightning Induced by Nearby Positive Cloud-to-Ground Lightning based on Highspeed Camera and Radio Frequency Mapping System

Abstract

Several lightning flashes observed on 325 m meteorological tower in Beijing, China. A high-speed video camera focused on the tower and four normal speed cameras focused on different directions that cover nearby high structures, the location of the towers is within the range of Beijing lightning network. In some thunderstorm, few of the positive lightning or intra-cloud flashes are initiating upward lightning from the towers. This work shows the features of the upward lightning due to these types of positive cloud to ground lightning near to towers. For this purposes, we have used highspeed video camera, normal speed camera, and radio frequency mapping data from Beijing Lightning NETwork (BLNET). BLNET, operated in Beijing-Tianjin-Hebei urban cluster area, has 16 stations and locates electromagnetic pulses radiated from cloud to ground and intra-cloud lighting. In nine of the analyzed flashes, two were simultaneously initiated upward lightning from different tower caused by same positive cloud to ground flash. Seven upward leaders were from single tower in which two of them were branched and in one case, the surface electric field was 3.5 kV/ m prior to the positive return stroke. In four cases, the upward leaders were associated with return stroke. Further, we considered tower lightning flash to validate our three-dimensional mapping of the flash and in the last a positive lightning three-dimensional development showed which initiated an upward leader.