The baroclinic annular mode (BAM) is the dominant mode of eddy kinetic energy in the Southern Hemisphere, characterized by a robust 20-30-day periodicity that significantly influences the atmospheric large-scale circulation and climate variability. Using the ERA5 reanalysis, CESM2 Large Ensemble, and CMIP model output, we observed an increase in the periodicity of the BAM under global warming, evidenced by the enhanced peak in the power spectrum of the BAM index (i.e., the leading principal component of eddy kinetic energy). Furthermore, we employed a simple model to investigate how climate change intensifies periodicity of BAM. The results show that the negative feedback between baroclinicity and eddy heat flux, which is essential to the BAM dynamics, has been modulated by climate change. Our research sheds light on the likelihood of augmented extreme weather events and shifts in precipitation patterns, offering critical insights for devising climate adaptation and mitigation strategies. Also, we observed substantial discrepancies across the CMIP models, highlighting the necessity for a meticulous evaluation of model performance related to eddy kinetic energy and storm tracks in these models.
 

atmospheric jet variability