16:45 〜 17:00
[AAS01-06] Future changes in the Asian summer monsoon precipitation projected by CMIP6 models
キーワード：夏季アジアモンスーン、地球温暖化、降水量
Understanding the future changes of the Asian summer monsoon (ASM) precipitation is necessary because the summer seasonal precipitation is an important water source for the region, and extremely wet and dry summers that its interannual variation brings in is generally related to floods and droughts. This study investigated the long-term changes in the ASM precipitation under global warming by analyzing results of Coupled Model intercomparison Project Phase 6 (CMIP6) models in the Shared Socioeconomic Pathways representative concentration pathway 585 (SSP585) scenario. From late June to late July, the ASM circulation dramatically develops. The Pacific High grows stronger over the North Pacific in the mid-latitudes, and the monsoon trough deepened and extended to the western North Pacific in the tropics. We analyzed in both seasonal and sub-monthly timescales to investigate whether the characteristics are different among the different phases of the development of the ASM circulation. We also focused on the Pacific–Japan (PJ) teleconnection pattern because it is one of the teleconnection patterns that influence summer weather in Japan.
The multi-model average based on 27 CMIP6 models projected that the climatological summer seasonal (June–August; JJA) precipitation increases in most parts of the ASM region, which agrees with the projection from the CMIP5 models reported by previous studies. However, the mean JJA precipitation over the South China Sea was projected to decrease. Its spatial pattern had a wet-get-wetter pattern, but the trend was weak compared to the projection by multi-model projection of the CMIP5 models.
In sub-monthly timescales, multi-model average based on five CMIP6 models (ACCESS-CM2, IPSL-CM6A-LR, MIROC6, MPI-ESM1-2-HR, MRI-ESM2-0) projected the increase of the mean ASM precipitation. The spatial pattern of long-term changes in the mean ASM precipitation diffed from late June to late July. The CMIP6 multi-model ensemble was able to reproduce the interannual variation of the PJ teleconnection pattern. The composite analysis showed that the CMIP6 models project that the interannual variation of the PJ teleconnection pattern would strengthen in the late 21st century. This result indicates that Japan may experience extreme heat that is induced by convective activity in the tropics.
The multi-model average based on 27 CMIP6 models projected that the climatological summer seasonal (June–August; JJA) precipitation increases in most parts of the ASM region, which agrees with the projection from the CMIP5 models reported by previous studies. However, the mean JJA precipitation over the South China Sea was projected to decrease. Its spatial pattern had a wet-get-wetter pattern, but the trend was weak compared to the projection by multi-model projection of the CMIP5 models.
In sub-monthly timescales, multi-model average based on five CMIP6 models (ACCESS-CM2, IPSL-CM6A-LR, MIROC6, MPI-ESM1-2-HR, MRI-ESM2-0) projected the increase of the mean ASM precipitation. The spatial pattern of long-term changes in the mean ASM precipitation diffed from late June to late July. The CMIP6 multi-model ensemble was able to reproduce the interannual variation of the PJ teleconnection pattern. The composite analysis showed that the CMIP6 models project that the interannual variation of the PJ teleconnection pattern would strengthen in the late 21st century. This result indicates that Japan may experience extreme heat that is induced by convective activity in the tropics.