Cyclone-Like Features Within the Stratospheric Polar-Night Vortex

• Main Authors: Davies, Huw C., Sprenger, Michael
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2024
• Subjects: stratosphere; polar night vortex; cyclones; stirring; sudden stratospheric warming; barotropic instability; Merra; polar night
• Online Access: https://hdl.handle.net/20.500.11850/682602; https://doi.org/10.3929/ethz-b-000682602

Distinctive synoptic-scale (∼1,500 km) flow features are identified within the core of the stratospheric polar-night vortex at stratopause altitudes (∼50 km). Typically they comprise a train or a complex pattern of transient vortices, each characterized by enhanced values of potential vorticity (PV) and relative vorticity but with a weaker thermal signal. In the MERRA-2 (and two other) reanalysis fields these cyclone-like features persist for several days, occur episodically, and form essentially within the core of the polar-night vortex itself. Their origin is plausibly linked to a form of barotropic instability associated with a radiatively-induced annular ring of enhanced PV. Moreover, their ubiquity and dynamics carries possible implications for: - the structure of the larger-scale polar vortex and its preconditioning ahead of a Sudden Stratospheric Warming event; the distribution of trace-constituents within the core; and the features representation in extended range/seasonal prediction and climate models. ISSN:0094-8276 ISSN:1944-8007