Abstract
Propagation patterns of 30- to 90-day boreal summer intraseasonal oscillation (BSISO) markedly affect subseasonal prediction. We show that global warming significantly alters BSISO propagation by Coupled Model Intercomparison Project Phase 6 projections. Under the Shared Socioeconomic Pathway 5-8.5 scenario, the eastward mode’s expansion propagation speed shows a twofold increase from 5.1 ± 1.9 to 10.3 ± 2.0 meters per second by the late 21st century, with a remarkable eastward extension by ~30° longitude compared to the present climate. The accelerated eastward mode frequency is expected to rise by 15%, intensifying subseasonal precipitation whiplash worldwide and shortening disaster preparedness time. This acceleration results from an asymmetric pattern of boundary layer moisture convergence anomalies, driven by weakened Rossby wave westerlies and enhanced Kelvin wave response linked to warming-induced atmospheric stabilization and El Niño–like ocean surface warming pattern. Conversely, a projected weakening of easterly vertical shear over the northern Indian Ocean attenuates the Rossby wave response and favors more eastward expansion events.
| Original language | English |
|---|---|
| Article number | eadv6355 |
| Pages (from-to) | 1-12 |
| Number of pages | 12 |
| Journal | Science Advances |
| Volume | 11 |
| Issue number | 38 |
| DOIs | |
| State | Published - Sep 17 2025 |
| Externally published | Yes |
Funding
Acknowledgments: We thank the two anonymous reviewers for their constructive comments that have substantially improved the manuscript. We acknowledge the World Climate Research Programme, which, through its Working Group on Coupled Modelling, coordinated and promoted CMiP6. We thank the climate modeling groups for producing and making available their model output, the earth System Grid Federation (eSGF) for archiving the data and providing access, and the multiple funding agencies who support CMiP6 and eSGF. nOAA interpolated Outgoing longwave Radiation (OlR) data are provided by the nOAA PSl, Boulder, Colorado, USA, from their website at https://psl.noaa.gov. Funding: this work was supported by hong Kong Research Grant Council General Research Fund: 16300424 (M.l.), hong Kong Research Grant Council Collaborative Research Fund: C6032-21G (M.l.), hong Kong Research Grant Council theme-based Research Scheme: t22-501/23-R (M.l.), hong Kong Research Grant Council Postdoctoral Fellowship Scheme: PdFS2324-6S05 (t.F.C.), national Science Foundation/Climate dynamics Award: 2025027 (B.W.), and national natural Science Foundation of China: 42175061 (F.l.). Author contributions: Conceptualization: B.W. and M.l. Methodology: t.F.C., B.W., and M.l. Software: t.F.C. validation: t.F.C., B.W., G.C., and M.l. Formal analysis: t.F.C. and B.W. investigation: t.F.C., B.W., F.l., and M.l. Resources: B.W. and M.l. data curation: t.F.C. Writing—original draft: t.F.C. and M.l. Writing—review and editing: t.F.C., B.W., F.l., G.C., and M.l. visualization: t.F.C. Supervision: B.W. and M.l. Project administration: B.W. and M.l. Funding acquisition: t.F.C., B.W., F.l., and M.l. Competing interests: the authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. the source of the CMiP6 model simulation output (34) is available at https://esgf-node.ipsl.upmc.fr/search/cmip6-ipsl/. the source of the nOAA-interpolated OlR dataset (81) is available at https://psl.noaa.gov/data/gridded/data.olrcdr.interp.html. the source of eRA5 reanalysis (82) is available at https://doi.org/10.24381/cds.adbb2d47.