3D Observations of Positive Cloud-to-Ground Flashes Using Interferometer

The field observations are conducted during winter thunderstorm. We obtained excellent data sets of positive CG flashe more than ten. Three-dimensional images of UHF radiation sources for positive CG flashes are shown. UHF radiation sources at leader progression stage show the tendency of concentration at constant altitude (2km, -5degrees) without any remarkable progression. On the other hand, after the return strokes the location of radiation sources proceeds very rapidly and penetrates into the thunderclouds horizontally. By applying the “Bi-directional leader concept”, 3D location of positive CG flashes is interpreted. The UHF radiation intensity of the negative leader is about 15 dBm stronger than that of the positive leader. Therefore, in case of 3D location of positive CG flashes, we can see negative leader propagating into thunderclouds, and we do not see positive leader tip coming down to ground.