Analysis of the Reproduction Features of the Guerrilla-heavy Rainfall and Estimation of Future Changes of the Occurrence Frequency in Multi-resolution RCMs

It has been increasingly important to project the future risk of small-scale torrential rainfall in summer, called ‘Guerrilla-heavy rainfall' in urban areas in Japan. In this study, we implemented some analysis in August in Kinki Region, from the view point of both the rainfall distribution and the unstable atmospheric condition. First, we picked up Guerrilla-heavy rainfall events with both tracking algorism and visual judgement of rainfall distribution of NHRCM05 output. Then, we analyzed the atmospheric stability of the events that was picked up, using a parameter SSI (Showalter Stability Index). As a result of T-test, it is implied that the number of days having Guerrilla-heavy rainfall will significantly increase at the end of August, and that this tendency corresponded to the more unstable SSI in the future. In conclusion, the season when Guerrilla-heavy rainfall is likely to occur will be longer in the future summer, with the more unstable SSI at the end of August