Event analysis of circulation anomalies in February 2024: troposphere - stratosphere coupling and the formation of the “Warm Arctic - Cold Eurasia” pattern
O.Yu. Antokhina1,2, P.N. Antokhin1, B.D. Belan1, O.S. Zorkaltseva2, A.V. Gochakov3, M.F. Artamonov2
1V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
2Institute of Solar-Terrestrial Physics of the Siberian Branch of the RAS, Irkutsk, Russia
3Institute of Computational Mathematics and Mathematical Geophysics of the Siberian Branch of the RAS, Novosibirsk, Russia
Keywords: temperature anomaly, Arctic, circulation, sudden stratospheric warming, atmospheric blocking, intrusion, ozone
Abstract
February 2024 was globally the record warmest; however, temperatures in southern Siberia were abnormally low, reaching -40 °C. That coincided with the anomalous “Warm Arctic - Cold Eurasia" (WACE) pattern. This study focuses on identifying the causes of this anomaly. Analysis of stratosphere-troposphere interactions revealed that the emergence of the WACE anomaly occurred simultaneously with the weakening of a stratospheric polar vortex (SPV) and a sudden stratospheric warming (SSW) in the second half of February 2024. Our findings confirm that the influence of SPV weakening on tropospheric anomalies occurs not only after SSW events but also during them. Anomalously strong stratosphere-troposphere exchange can induce localized and prolonged cold spells in the troposphere over Siberia. These conclusions are supported by wave activity flux calculations based on reanalysis data and instrumental observations during aircraft-based sounding. Our research highlights the crucial role of complex interactions between the troposphere and stratosphere in shaping and amplifying climate anomalies, such as WACE, in winter.
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