Conference Paper Relative contributions of different weather systems to the changes in annual mean and extreme precipitation in CMIP5 models

内海, 信幸  ,  Nobuyuki, Utsumi  ,  金, 炯俊  ,  KIM, Hyungjun  ,  鼎, 信次郎  ,  Kanae, Shinjiro  ,  沖, 大幹  ,  Oki, Taikan

Future changes in precipitations due to climate change are of great concern to society. Changes in the precipitation is expected to be caused by the changes in various weather systems (e.g., tropical cyclones). However, questions such as “Which weather systems will cause which changes?” and “Is the relative importance of these weather systems likely to change in the future?” have not been addressed fully yet. Here, we present the global estimates of the relative contributions of different weather systems (i.e., tropical cyclones, extratropical cyclones including fronts, and the others) to changes in annual mean and extreme precipitations in the late 21st century using multi-model projections of the Coupled Model Intercomparison Project Phase 5 (CMIP5). The weather systems are identified from atmospheric fields of CMIP5 simulations at every 6-hour using objective detection method. Precipitation within a certain distance from a weather system is regarded to be associated with the weather system. The proportions of weather system-wise precipitation in annual mean and extreme precipitation are estimated for the present and future climate. It is found that the subtropics, particularly in the Pacific and North Atlantic, are the regions where the notable changes of the proportions are detected. Given that the proportion of weather systems is one of the important factors which characterize the climate regime of each region, the change in the proportion indicates the shift of climate regime of the region. The contributions of weather systems to future changes in precipitation are also quantified. In regions where a shift of the climate regime is projected, even a minor weather system in the present climate can cause considerable changes in annual and extreme precipitation.

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