Yoshinobu Masuda

Abstract

Uda et al. (1953) investigated the so-called 'black rain' 1-4 months after the Hiroshima A-bomb in August 1945. In their report, they described two rainfall areas: a 'heavy rain area' and a 'light rain area'. The heavy rain area was oval shaped, with a long axis of 19 km and a minor axis of 11 km; the 'light rain area' was also oval shaped, with a long axis of 29 km and a minor axis of 15 km. The map of the heavy rain area has been used in a support system for A-bomb survivors by the government of Japan. Uda et al.'s sample size of rainfall reports from survivors was only 170, so it was possible that their maps might not include the entire rainfall area. Masuda (1989) therefore re-investigated the black rain area using a much larger data set and reported revised results. In addition to the data used by Uda et al., Masuda used new questionnaires, hearing results, reports of survivors, and other sources to make a revised rainfall area map. The width of the rainfall area was 4 times or more that reported by Uda et al., and the shape was more complex. The start times, duration, and estimated amount of precipitation of black rain were also reported. This paper is a review of Masuda's paper, which was written in Japanese for the journal Tenki in 1989.