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Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The performance of Version 2 of the Flexible Global Ocean-Atmosphere-Land System model (FGOALS-s2) in simulating global monsoon precipitation (GMP) was evaluated. Compared with FGOALS-s1, higher skill in simulating the annual modes of climatological tropical precipitation and interannual variations of GMP are seen in FGOALS-s2. The simulated domains of the northwestern Pacific monsoon (NWPM) and North American monsoon are smaller than in FGOALS-s1. The main deficiency of FGOALS-s2 is that the NWPM has a weaker monsoon mode and stronger negative pattern in spring-fall asymmetric mode. The smaller NWPM domain in FGOALS-s2 is due to its simulated colder SST over the western Pacific warm pool. The relationship between ENSO and GMP is simulated reasonably by FGOALS-s2. However, the simulated precipitation anomaly over the South African monsoon region-South Indian Ocean during La Niña years is opposite to the observation. This results mainly from weaker warm SST anomaly over the maritime continent during La Niña years, leading to stronger upper-troposphere (lower-troposphere) divergence (convergence) over the Indian Ocean, and artificial vertical ascent (descent) over the Southwest Indian Ocean (South African monsoon region), inducing local excessive (deficient) rainfall. Comparison between the historical and pre-industrial simulations indicated that global land monsoon precipitation changes from 1901 to the 1970s were caused by internal variation of climate system. External forcing may have contributed to the increasing trend of the Australian monsoon since the 1980s. Finally, it shows that global warming could enhance GMP, especially over the northern hemispheric ocean monsoon and southern hemispheric land monsoon. [ABSTRACT FROM AUTHOR]

East Asia has experienced a significant interdecadal climate shift since the late 1970s. This shift was accompanied by a decadal change of global SST. Previous studies have suggested that the decadal shift of global SST background status played a substantial role in such a climatic shift. However, the individual roles of different regional SSTs remain unclear. In this study, we investigated these roles using ensemble experiments of an atmospheric general circulation model, GFDL (Geophysical Fluid Dynamics Laboratory) AM2. Two kinds of ensembles were performed. The first was a control ensemble in which the model was driven with the observed climatological SSTs. The second was an experimental ensemble in which the model was driven with the observed climatological SSTs plus interdecadal SST background shifts in separate ocean regions. The results suggest that the SST shift in the tropics exerted more important influence than those in the extratropics, although the latter contribute to the shift modestly. The variations of summer monsoonal circulation systems, including the South Asian High, the West Pacific Subtropical High, and the lower-level air flow, were analyzed. The results show that, in comparison with those induced by extratropical SSTs, the shifts induced by tropical SSTs bear more similarity to the observations and to the simulations with global SSTs prescribed. In particular, the observed SST shift in the tropical Pacific Ocean, rather than the Indian Ocean, contributed significantly to the shift of East Asian summer monsoon since the 1970s. [ABSTRACT FROM AUTHOR]