85th AMS Annual Meeting

Monday, 10 January 2005
Change of the East Asian summer rainy season (Bai-u) projected by a super high resolution global model
Shoji Kusunoki, Meteorological Research Institute, Climate Research Department, 4th Laboratory (Global warming projection), 305-0052, Tsukuba, Ibaraki, Japan
The future climate changes were investigated using an Atmosphere-Ocean General Circulation Model (AOGCM) and a super high resolution AGCM with 20 km spacing. This study was conducted under the framework of the Research Revolution 2002 (RR2002) project "Development of Super High Resolution Global and Regional Climate Models" funded by Ministry of Education, Culture, Sports, Science and Technology (MEXT). The whole experiments consist of three steps. In the first step, the time evolutions of sea surface temperature (SST) till year 2100 were projected by MRI-CGM Version 2.3 for the "A1B" emission scenario of greenhouse gases. Atmospheric part of MRI-CGM has the horizontal resolution of about 270 km with 30 layers. Oceanic part has the horizontal resolution of 2 degree in latitude and 2.5 degree in longitude with 23 layers. The flux adjustment is used for heat and freshwater. In the second step, the 20 km horizontal resolution AGCM was forced with observed climatological SST (1982-1998, 12 year mean) to simulate present climate. Integration time is 10 years. In the third step, the projected SST change from present (1979-1998, 20 year mean) to future (2080- 2099, 20 year mean) was added to the present observed climatological SST to construct future SST. Then, the 20 km horizontal resolution AGCM was forced with the future SST for 10 years. Carbon dioxide concentration in the atmosphere is nearly doubled in about year 2090. Difference between the second step experiment (present 10 years including year about 1990) and the third step experiment (future 10 years including year about 2090) was regarded as climate change for the next 100 years. In the future climate, it was found that precipitation over Western Japan, East China Sea, Yangtze river valley of China increases in summer rainy season Increase of precipitation can be related to the intensification of clockwise moist flow associated with the stronger subtropical high. In contrast, decrease of precipitation was found over Korea and northern part of China.

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