Future changes in precipitation of the baiu season under RCP scenarios

Recently, the relationship between global warming and rainfall during the rainy season, which called the baiu in Japan, has been attracting attention in association with heavy rainfall in this period. In the Innovative Program of Climate Change Projection for the 21^st Century, many studies show a delay in the northward march of the baiu front, and significant increase of daily precipitation amounts around western Japan during the late baiu season (e.g., Kusunoki et al. 2011, Kanada et al. 2012). The future climate experiment in these studies was performed under the IPCC SRES A1B scenarios for global warming conditions.

In this study, we discuss the future changes in precipitation using calculated 60km-mesh model (MRI-AGCM3.2H) under Representative Concentration Pathways (RCP) scenarios. Support of this dataset is provided by the Meteorological Research Institute (MRI). These dataset are calculated by setting the Yoshimura (YS) scheme mainly.

Seasonal progression of future precipitation generally indicates the northward in RCP2.6 and 4.5 scenarios, around western Japan. In RCP6.0 scenario, precipitation intensity is weak compared to the other scenarios. RCP8.5 scenario is calculated by setting three different cumulus schemes (YS, Arakawa-Schubert (AS), and Kain-Fritsch (KF) schemes). RCP8.5 configured in YS scheme showed that the rainband associated with the baiu front is not clear. Moreover, peak is remarkable during late June. In AS scheme, the precipitation area stagnates around 30 N until August. And it in KF scheme shows gradual northward migration.

This work was conducted under the Program for Risk Information on Climate Change supported by the Ministry of Education, Culture, Sports, Science, and Technology-Japan (MEXT).