Abstract
The upper-level tropical easterly jet (TEJ) is a crucial component of the summer monsoon system and tropical general circulation. The simulation and projection of the TEJ, however, have not been assessed. Here we evaluate models’ fidelity and assess the future change of the TEJ by utilizing 16 models that participated in phase 6 of the Coupled Model Intercomparison Project (CMIP6). Most of the models can reproduce the TEJ reasonably well in terms of climatology, seasonal evolution, and interannual variability. Nevertheless, underestimation of the TEJ’s intensity and extent is identified, with the maximum bias occurring in the jet centers over the tropical Indian Ocean (IO) and the tropical eastern Pacific (EP). Under the shared socioeconomic pathway 5–8.5, the multimodel ensemble projects a remarkable reduction in the central TEJ intensity by about 18% over the IO and 77% over the EP toward the end of the twenty-first century. The mean intensity of TEJ will weaken by about 11%, and the extent will reduce by 6%, suggesting a significantly weakened upper-level monsoon circulation in the future climate. The projected El Niño–like warming pattern over the tropical Pacific may play a critical role in the future weakening of the TEJ via inducing suppressed rainfall over the tropical eastern IO and Central America. The model uncertainties in the projected TEJ changes may arise from the uncertainties in the models’ projected tropical EP warming. The sensitivity of future projections to model selection is also examined. Results show that the selection of models based on different physical considerations does not yield a significantly different projection.
| Original language | English |
|---|---|
| Pages (from-to) | 8439-8455 |
| Number of pages | 17 |
| Journal | Journal of Climate |
| Volume | 33 |
| Issue number | 19 |
| DOIs | |
| State | Published - Oct 1 2020 |
| Externally published | Yes |
Funding
Acknowledgments. The authors thank the three anonymous reviewers for their constructive comments to significantly improve the manuscript. We acknowledge the World Climate Research Programme’s Working Group on Coupled Modeling, which is responsible for the CMIP. We thank the Earth System Grid Federation for data dissemination and climate modeling groups listed in Table 1 of this paper. This research is jointly supported by National Key Research and Development Program of China (2016YFA0600601) and National Natural Science Foundation of China (41530530, 41875087). B.W. acknowledges the support of NSF/Climate Dynamics Award AGS-1540783. This is the International Pacific Research Center (IPRC) Publication No. 1454, School of Ocean and Earth Science and Technology (SOEST) Publication No. 11093, and Earth System Modeling Center (ESMC) Publication No. 314.