Stratospheric polar vortex, wave absorption/reflection and effect on surface climate

Abstract The study of the stratosphere-troposphere interaction is important as it can contribute to boosting predictability in the subseasonal-to-seasonal timescale, particularly regarding extremes. This manuscript investigates the relationship between the stratospheric polar vortex and its sudden stratospheric warming and the troposphere in regard to the reflective and absorptive states of the vortex. We explore the eddy heat flux in relation to vertical wave propagation and sudden stratospheric warming, in addition to using the reflective index for comparison and checking. To find reflective and absorptive vortex regime and associated tropospheric flow, the analysis is complemented by clustering analysis. Using northern winter stratospheric and mid-tropospheric Reanalysis heights as well as sea level pressure and 2 m-temperature, absorptive and reflective states are identified and their coherent structures investigated in relation to the vortex state and surface climate. While the reflective index is not consistent with the eddy heat flux on the classification, the absorptive type for both methods consistently trigger a response in the annular mode with a negative Arctic Oscillation imprint. It also exhibits longer lasting wave propagation, compared to reflective types, suggesting sustained disruption of the circulation and occurrence of blocking. The clustering analysis reveals specific characteristics within vortex states affecting wave propagation. Precisely, weak and displaced or split vortex over the eastern hemisphere is associated with absorptive type, and yields more persistence, compared to the reflective type, associated with strong or quite weak vortex and also displaced vortex over North America. Effect on the surface climate are also discussed.