Abstract
UHF interferometers were operated during winter thunderstorm observations in Japan. Tbe main objective is the investigation of lightning channel progressions inside thunderclouds, especially for positive cloud to ground strikes. Since the time resolution of interferometers is high, observation results are used additionally to confirm the upward initiated leader formation by laser firing. Lightning currents measured by Rogowski coils and electric field changes are compared with UHF radiation to confirm leader formation. All of the observations are consistent with the time accuracy of 17 μ seconds and this paper strongly claims the first success of laser triggered lightning experiment in the field.
