A bias-corrected projection for the changes in East Asian summer monsoon rainfall under global warming
Projecting regional rainfall changes in a warmer climate attracts ongoing attention. However, large uncertainty still exists in multi-model projection. In this study, we introduce a bias-corrected method to correct the multi-model projection of changes in East Asian summer monsoon (EASM) rainfall based on the historical and RCP8.5 runs of 25 models from phase 5 of Coupled Model Intercomparison Project. Firstly, the total rainfall changes are separated into the thermodynamic component due to increased specific humidity and the dynamic component due to circulation changes. The thermodynamic component is corrected using the observed present-day rainfall and the increase rate of specific humidity based on the wet-get-wetter mechanism. On the other hand, the dynamic component with the circulation changes is corrected based on a “spatial emergent constraint” method, which is further validated by the perfect model approach. Together, these corrections give an integrated projection for EASM rainfall changes under global warming. Such an approach can improve the signal-to-noise ratio of projection effectively, from the original 0.73 of the multimodel mean to around 1.9. The corrected projection of EASM rainfall changes shows a pronounced increase in southern China, the northwest Pacific and a belt from northern China to northeastern China, and a weak increase in other EASM regions.
KeywordsEast Asian summer monsoon Rainfall Bias correction CMIP5 Global warming
This work is supported by the National Natural Science Foundation of China (41575088, 41722504, 41425019, 41721004 and 41661144016), the Strategic Priority Research Program of Chinese Academy of Sciences (XDA20060501), the Public Science and Technology Research Funds Projects of Ocean (201505013), and the Youth Innovation Promotion Association of CAS and the Fundamental Research Funds for the Central Universities. We acknowledge the World Climate Research Programme’s Working Group on Coupled Modeling, which is responsible for CMIP5, and the climate modeling groups (listed in Table 1) for producing and making available their model output. We also thank two anonymous reviewers for their constructive suggestions.
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