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Increased synoptic variability along the subtropical Meiyu front under global warming


Dominant summertime disturbances along the subtropical Meiyu front are eastward-propagating synoptic-scale waves coupled with precipitation and moisture under a moderate background vertical shear. To what extent the intensity and structure of such synoptic disturbances would change under global warming is investigated by diagnosing 18 models from Phase 6 of the Coupled Model Intercomparison Project (CMIP6). The model diagnosis reveals that there is a robust increase in the intensity of synoptic-scale motions along the Meiyu front, while the wavelength and phase speed remain unchanged. The cause of such changes of the synoptic-scale variability in the future warmer climate is investigated through the analysis of a moist baroclinic instability model. It is found that the growth rate of the most unstable mode strengthens in the future warmer climate, while the zonal wavenumber and phase speed of the most unstable mode remain unchanged, which is consistent with the CMIP6 projections. The enhanced synoptic-scale variability is primarily attributed to the increase of background meridional and vertical moisture gradients under a warmer climate through strengthened positive moisture-convection-circulation feedback, while the changes of background vertical shear and convective adjustment times are insignificant.

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Data availability

The CMIP6 model outputs are available from The Global Precipitation Climatology Project (GPCP) data can be obtained from The ERA5 reanalysis data can be downloaded from–reanalysis.


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The authors acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling and the climate modelling groups for producing and making available their model output. The authors thank the Earth System Grid Federation (ESGF) for archiving the data and providing access, and the multiple funding agencies who support CMIP6 and ESGF. The authors acknowledge the European Centre for Medium-Range Weather Forecasts for providing the ERA5 reanalysis data. The authors acknowledge the Global Precipitation Climatology Project for providing the precipitation data used in the study.


This work was jointly supported by NSFC grant 42088101, NOAA NA18OAR4310298, and NSF AGS-2006553. This is SOEST contribution number 11596 and IPRC contribution number 1583.

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All authors designed the study. GY performed the analysis and prepared figures. GY wrote the main manuscript. All authors discussed the results and revised the manuscript.

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Correspondence to Tim Li.

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Yang, G., Li, T. Increased synoptic variability along the subtropical Meiyu front under global warming. Clim Dyn (2022).

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  • Synoptic-scale disturbances
  • Meiyu front
  • Moist baroclinic instability
  • Most unstable mode
  • Global warming projections