Using state-of-the-art models from the Coupled Model Intercomparison Project Phases 5 and 6 (CMIP5/6), future changes of sudden stratospheric warming (SSW) events under a moderate emission scenario (RCP45/SSP245) and a strong emissions scenario (RCP85/SSP585) are evaluated with respect to the historical simulations. Changes in four characteristics of SSWs are examined in 54 models: the SSW frequency, the seasonal distribution, stratosphere-troposphere coupling, and the persistency of the distorted or displaced polar vortex. The composite results show that none of these four aspects will change robustly. An insignificant (though positive) change in the SSW frequency from historical simulations to RCP45/SSP245 and then to RCP85/SSP585 is consistently projected by CMIP5 and CMIP6 multimodel ensembles in most wintertime months (December-March). This increase in the SSW frequency is most pronounced in mid- (late-) winter in CMIP6 (CMIP5). No shift in the seasonality of SSWs is simulated especially in the CMIP6 future scenarios. Both the reanalysis and CMIP5/6 historical simulations exhibit strong stratosphere-troposphere coupling during SSWs, and the coupling strength is nearly unchanged in the future scenario simulations. The near surface responds immediately after the onset of SSWs in both historical and future scenarios experiments, denoted by the deep downward propagation of zonal-mean easterly anomalies from the stratosphere to the troposphere. On average, the composite circumpolar easterly winds persist for 8 d in the reanalysis and CMIP5/6 historical experiments, which are projected to remain unchanged in both the moderate and strong emissions scenarios, implying the lifecycle of SSWs will not change.
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Original content from this work may be used under the terms of the . Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. National Natural Science Foundation of China http://dx.doi.org/10.13039/501100001809 41705024 ISF-NSFC joint research program 3259/19 H2020 European Research Council http://dx.doi.org/10.13039/100010663 677756 yes � 2021 The Author(s). Published by IOP Publishing Ltd Creative Commons Attribution 4.0 license
The authors thank the ESGF (https://esgf-node. llnl.gov/projects/esgf-llnl/) for their freely providing the CMIP5/6 simulations. All CMIP5/6 data used in this study are publicly available. The CMIP5/6 models (see tables 1 and 2) are developed by different agencies from different countries. This work was supported by the National Key R&D Program of China (2016YFA0602104) and the National Natural Science Foundation of China (41705024). CIG is also funded by the ISF-NSFC joint research program (3259/19) and the European Research Council starting grant under the European Union's Horizon 2020 research and innovation programme (677756).
© 2021 The Author(s). Published by IOP Publishing Ltd
- Future projection
- Sudden stratospheric warming (SSW)