Breaking of Rossby waves in the stratosphere. Part II. Factors leading to sudden stratospheric warmings
O.Yu. Antokhina1,2, A.V. Gochakov1,3, O.S. Zorkal’tseva2, P.N. Antokhin1, V.N. Krupchatnikov4, 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
3Siberian Regional Hydrometeorological Research Institute, Novosibirsk, Russia
4Institute of Computational Mathematics and Mathematical Geophysics of the Siberian Branch of the RAS, Novosibirsk, Russia
Keywords: stratosphere, planetary wave breaking, Rossby wave breaking, sudden stratospheric warming, circulation anomaly, temperature
Abstract
Based on a developed and adapted method for identifying Rossby wave breaking (RWB), which accounts for the specifics of stratospheric circulation, an analysis of the conditions for the occurrence of major sudden stratospheric warmings (SSWs) in the Northern Hemisphere was conducted. The method relies on examining the geometry of potential vorticity contours in the stratosphere at the 850 K level using ERA5 reanalysis data. It is shown that anomalous RWB processes in November and December play a key role in preparing for the onset of SSWs. Most of the analyzed SSW events are associated with an increase in the number of RWB events in the Asia-Pacific (AP) region in November and December, and occasionally in January. In cases where SSW initiation is linked to RWB over the Atlantic and Europe, it is also preceded by RWB anomalies in the AP region. For the identified types of wave breaking in the stratosphere, atmospheric blocking is characteristic in the troposphere, accompanied by negative near-surface temperature anomalies over Eurasia and/or North America. The increased frequency of early and middle major SSW events aligns with the previously identified trend of enhanced negative temperature responses to atmospheric blocking in the Northern Hemisphere.
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