There is growing concern on a global scale about the significant increase of extreme meteorological events in recent years, e.g., torrential rains, heavy snows, and severe hurricanes. The current study conducted frequency and scale analysis of torrential rains to examine future variations of rainfall events due to global warming, based on GCM (Global Climate Model) outputs calculated under the present condition (1979-2008), near-future condition (2015-2044), and future condition (2075-2104) by the KAKUSHIN Program of the Ministry of Education, Culture, Sports, Science, and Technology (MEXT). DAD analysis was also attempted to clarify whether and how the statistical relationship will change in the future with global warming between maximum areal rainfall and the area and duration of each rainfall event. Results show that the occurrence frequency of torrential rains could markedly increase in some regions of Japan, and that DAD relationship could significantly change in the future, and there could be a numerical increase in rainfall events which depart from the regression curve of DAD relationship due to a greater rainfall intensity or larger area of rainfall than most other events. Visual inspections of each event suggest that such extreme events could be attributed to Baiu front activated by the sufficient amount of water vapor and typhoons strengthened by the higher sea surface temperature due to global warming in the future.
