Abstract
Projecting future change of monsoon rainfall is essential for water resource management, food security, disaster mitigation, and infrastructure planning. Here we assess the future change and explore the causes of the changes using 15 models that participated in phase 6 of the Coupled Model Intercomparison Project (CMIP6). The multimodel ensemble projects that, under the shared socioeconomic pathway (SSP) 2-4.5, the total land monsoon rainfall will likely increase in the NorthernHemisphere (NH) by about 2.8%per one degree Celsius of global warming (2.8% 8C21) in contrast to little change in the Southern Hemisphere (SH; 20.3% 8C21). In addition, in the future the Asian-northern African monsoon likely becomes wetter while the North American monsoon becomes drier. Since the humidity increase is nearly uniform in all summer monsoon regions, the dynamic processes must play a fundamental role in shaping the spatial patterns of the global monsoon changes. Greenhouse gas (GHG) radiative forcing induces a "NH-warmer-than-SH" pattern, which favors increasing the NHmonsoon rainfall and prolonging theNHmonsoon rainy seasonwhile reducing the SHmonsoon rainfall and shortening the SHmonsoon rainy season. TheGHGforcing induces a "land-warmer-than-ocean" pattern,which enhances Asian monsoon low pressure and increases Asian and northern African monsoon rainfall, and an El Ninõ-like warming, which reduces North American monsoon rainfall. The uncertainties in the projected monsoon precipitation changes are significantly related to the models' projected hemispheric and land-ocean thermal contrasts as well as to the eastern Pacific Ocean warming. The CMIP6 models' common biases and the processes by which convective heating drives monsoon circulation are also discussed.
| Original language | English |
|---|---|
| Pages (from-to) | 6471-6489 |
| Number of pages | 19 |
| Journal | Journal of Climate |
| Volume | 33 |
| Issue number | 15 |
| DOIs | |
| State | Published - Aug 1 2020 |
| Externally published | Yes |
Funding
Acknowledgments. The authors appreciate three reviewers’ constructive comments on an earlier version of the paper, which lead to an improved presentation. The first author thanks Prof. Brian Hoskins for helpful e-mail discussion. This work was supported by the National Natural Science Foundation of China (Grants 41420104002, and 41971108). Authors Liu and Wang are supported by the National Key Research and Development Program of China (Grant 2016YFA0600401). Wang acknowledges the support of NSF/Climate Dynamics Award AGS-1540783. Author Jin acknowledges the support from the program of China Scholarships Council (201806860029). This is Publication Number 10981 of the School of Ocean and Earth Science and Technology, Publication Number 1445 of the International Pacific Research Center, and Publication Number 310 of the Earth System Modeling Center.