Changes in future weather extremes are projected using a global atmospheric general circulation model and a non-hydrostatic regional climate model under the global warming environment in the near future (2030s) and at the end of the 21st century. The global 20-km mesh model can simulate tropical cyclones more realistically in their strength, structure and geographical distribution together with associated heavy rainfall and strong surface winds as compared with lower resolution models. According to the SRES A1B scenario, it is projected that at the end of the 21st century there will be a 40%∼60% increase in precipitation and a 15%∼20% increase in surface wind speeds within a 100 km radius of the tropical cyclone center. Ensemble simulations using the global 60-km model version are performed to obtain information on the uncertainty of projections. Downscaling with the 5-km mesh non-hydrostatic regional climate model is also performed for the Japanese summer rainy season. It is found that the frequency of heavy precipitation will increase in the future for the hourly as well as daily precipitation. In particular, the strong hourly precipitation will increase even in near future: 99.9%-ile value of hourly precipitation increases 7% in the near future and 21% at the end of the 21st century.
2009 Japan Society of Hydrology and Water Resources