Abrupt and persistent atmospheric circulation changes in the North Atlantic under La Niña conditions

• Published in: Weather and Climate Extremes
• Main Authors: García Burgos, Marina, Gómara, Íñigo, Rodríguez Fonseca, Belén, González-Alemán, Juan Jesús, Zurita Gotor, Pablo, Ayarzagüena, Blanca
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2023
• Subjects: Atmospheric circulation; Sudden Stratospheric Warming; North Atlantic Oscillation; North Atlantic cyclones; Pacific; North Atlantic; North Atlantic oscillation
• Online Access: https://hdl.handle.net/20.500.11765/15188

Several recent studies have linked the exceptional North Atlantic and Eurasian atmospheric evolution during late February and March 2018 to the Sudden Stratospheric Warming (SSW) that took place a few weeks earlier. February 2018 was characterized by an abrupt transition from the positive to the negative phase of the North Atlantic Oscillation (NAO) and a subsequent persistence of the negative NAO for several weeks. This paper investigates the contribution of atmospheric and oceanic phenomena to both the 2018 event and a set of 19 identified analogues (including the former) for the period 1959–2022. Evidence is given that La Niña conditions in the tropical Pacific and upstream North Atlantic cyclones play an important role as a trigger for these events. Ensuing two-way tropospheric-stratospheric coupling and eddy feedbacks provide extended-range persistence for negative NAO conditions. These results may help improve the prediction of such exceptional events. This research was funded by the projects EU-H2020 TRIATLAS (no. 817578), Universidad Complutense de Madrid FEI-EU-19-09, Spanish-MINECO PRE4CAST (CGL2017-86415-R) and JeDiS (RTI2018-096402-B-I00). Also supported by the Grant PRE2019-090618 from Spanish Ministerio de Ciencia e Innovacion.