The Projection and Uncertainty Analysis of Summer Precipitation in China and the Variations of Associated Atmospheric Circulation Field

Monthly data from climate change simulations based on the 15 coupled climate system models in IPCC SRES (Special Report on Emissions Scenarios) A2, A1B, and B1 are analyzed for potential future changes in summer precipitation characteristics and its associated atmospheric circulation, and the uncertainties of these results from models are also investigated. The results demonstrate that the projected summer precipitation in China shows distinctly regional characteristics. The summer precipitation in the eastern part of China and the Tibetan Plateau are projected to significantly increase in the 21st century. These increasing linear trends and the consistency of the models are also intensified with the increase of air temperature, which indicates that the projections become much more believable in these regions. However, persistent decrease of summer precipitation is projected in the southern part of Xinjiang region, and most of models show decreasing precipitation in the earlier period of the 21st century and then increasing in Southwest China. No obvious changes are projected in the other parts of China, but with larger uncertainties. The high confidence level of the multiple models ensemble results in IPCC three scenarios implies that the projected summer precipitation changes are much more believable in China, with the larger projection in A2, smaller in B1, and middle in A1B.Most of the models demonstrate that the East Asian summer monsoon will significantly intensify under global warming, which induces more water vapor transport from the South China Sea and the tropical oceans. Thus, more water vapor content will be gathered that provides a benefit background for the increasing summer precipitation in the eastern part of China. Meanwhile, the western Pacific subtropical high is also projected to significantly intensify and the impacts on the summer precipitation in the eastern part of China also obviously increase. These results from the analysis of the atmospheric circulation and the corresponding uncertainties of the models further increase the confidence level of the projected summer precipitation change in China.