Radar echo structure of thunder clouds observed at Shigaraki, Japan in the Baiu season 1991

Abstract

Three cases of lightning at Shigaraki, Japan during the Baiu season in 1991 were observed with an X-band dual-polarization Doppler radar. Structures of radar echoes analyzed with a conventional C-band radar and the X-band radar data were compared with lightning locations obtained by LLP and SAFIR. Six hourly radiosonde data at Shigaraki were also utilized to analyze the vertical thermodynamic structures. At 03 JST 5 July, lightnings were observed more than 15 km behind an arc shaped strong echo (>45 dBZ) which height was less than 4 km (below melting layer). The role of moist and unstable layer below melting layer to form thunderclouds was discussed for three cases.