Minor Sudden Stratospheric Warmings: A Relationship between the Spatial Organization of Rossby Wave Breaking and Evolution of Thermal Anomalies in the Lower Troposphere

The paper presents the results of studying minor sudden stratospheric warmings (SSWs) that were obtained using an original methodology that combines identifying Rossby wave breaking (RWB) with analyzing of potential vorticity fields on the 850 K isentropic surface based on ERA5 reanalysis data. The main focus is on the spatiotemporal features of wave activity in key regions of the Northern Hemisphere. Characteristic scenarios of minor SSW development were revealed, including cases of compensatory interaction between wave disturbances, which leads to stabilization of the stratospheric polar vortex. It is found that as compared to major sudden stratospheric warmings, the role of RWB events formed in the Euro-Atlantic sector is increasing for minor SSWs. The enhanced meridional circulation periods associated with the Ural blocking are on average less stationary than those during major SSWs and do not form persistent cold patterns over Siberia (although individual events may deviate from this pattern). The identified features of the spatial organization of RWB and its relationship with thermal anomalies are important for improving methods for diagnosing and predicting stratosphere–troposphere coupling.