Overview of Lightning Current Observation at Tokyo Skytree

Direct observation of lightning current is a fundamental approach to evaluating lightning parameters, which are among the most basic factors for the lightning protection design of various grounded objects. However, for a tall grounded structure, upward lightning flashes initiated from the top of the structure have usually been observed, and the direct observation results of downward flashes have been limited. Tokyo Skytree is a free-standing independent broadcasting tower, which height is 634m-ASL, located on a flat terrain about 8 km inland in Tokyo, Japan (35.71°N, 139.81°E). The authors have conducted lightning current observation with the Rogowski coils at the tower since 2012. At Tokyo Skytree, we have confirmed 38 downward-initiated lightning flashes and 69 upward-initiated lightning flashes to the tower as of the end of December 2022 for 11 years. In this paper, we overview the lightning current observation and the recent result at Tokyo Skytree.