2026-06-27T12:24:19Zhttps://docta.ucm.es/rest/oai/request

oai:docta.ucm.es:20.500.14352/1083422025-03-18T15:58:19Zcom_20.500.14352_14col_20.500.14352_15

Díaz Durán, Adelaida Serrano Mendoza, Encarnación Ayarzagüena Porras, Blanca Ábalos Álvarez, Marta De La Cámara Illescas, Álvaro 2024-09-23T16:01:11Z 2024-09-23T16:01:11Z 2017-01-20 Díaz-Durán, A., Serrano, E., Ayarzagüena, B., Abalos, M., & de la Cámara, A. (2017). Intra-seasonal variability of extreme boreal stratospheric polar vortex events and their precursors. Climate Dynamics, 49, 3473-3491. 0930-7575 10.1007/s00382-017-3524-1 https://hdl.handle.net/20.500.14352/108342 1432-0894 https://doi.org/10.1007/s00382-017-3524-1 https://link.springer.com/article/10.1007/s00382-017-3524-1 The dynamical variability of the boreal stratospheric polar vortex has been usually analysed considering the extended winter as a whole or only focusing on December, January and February. Yet recent studies have found intra-seasonal differences in the boreal stratospheric dynamics. In this study, the intra-seasonal variability of anomalous wave activity preceding polar vortex extremes in the Northern Hemisphere is examined using ERA-Interim reanalysis data. Weak (WPV) and strong (SPV) polar vortex events are grouped into early, mid- or late winter sub-periods depending on the onset date. Overall, the strongest (weakest) wave-activity anomalies preceding polar vortex extremes are found in mid- (early) winter. Most of WPV (SPV) events in early winter occur under the influence of east (west) phase of the Quasi-Biennial Oscillation (QBO) and an enhancement (inhibition) of wavenumber-1 wave activity (WN1). Mid- and late winter WPV events are preceded by a strong vortex and an enhancement of WN1 and WN2, but the spatial structure of the anomalous wave activity and the phase of the QBO are different. Prior to mid-winter WPVs the enhancement of WN2 is related to the predominance of La Nia and linked to blockings over Siberia. Mid-winter SPV events show a negative phase of the Pacific-North America pattern that inhibits WN1 injected into the stratosphere. This study suggests that dynamical features preceding extreme polar vortex events in mid-winter should not be generalized to other winter sub-periods. eng open access Intra-seasonal variability of extreme boreal stratospheric polar vortex events and their precursors journal article