Modulations in the planetary wave field induced by upward‐propagating Rossby wave packets prior to stratospheric sudden warming events: A case‐study

• Published in: Quarterly Journal of the Royal Meteorological Society
• Main Authors: Nishii, Kazuaki, Nakamura, Hisashi, Miyasaka, Takafumi
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2009
• Subjects: Antarc*; Antarctica; North Atlantic
• Online Access: http://dx.doi.org/10.1002/qj.359; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fqj.359; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.359

Abstract A diagnostic framework is introduced in which anomalous zonally averaged Rossby wave‐activity injection into the stratosphere is decomposed into a contribution solely from zonally confined upward‐propagating Rossby wave packets and another from interaction of the wave packets with the climatological planetary waves. To pinpoint the tropospheric sources of the wave packets, a particular form of wave‐activity flux is evaluated for the associated circulation anomalies. The framework is applied to reanalysis data for the period prior to a stratospheric sudden warming (SSW) event in January 2006, which was associated with two successive events of above‐normal wave‐activity injection from the troposphere. In the earlier event, a pair of wave packets that emanated from tropospheric anomalies over the North Pacific and over Europe enhanced the upward wave‐activity injection, which was augmented further by their interaction with the climatological planetary wave. In contrast, in the later period a wave packet that emanated from an anticyclonic anomaly over the North Atlantic is found to be the primary contributor to the enhanced planetary wave‐activity injection, while its interaction with the climatological planetary wave contributed negatively. The predominant importance of the sole contribution from a single wave packet is also found in a major SSW event observed over Antarctica in September 2002. These results indicate that the diagnostic framework presented in this study is a useful tool for understanding the interaction between anomalies associated with zonally confined wave packets and climatological‐mean planetary waves in the study of stratosphere‐‐troposphere dynamical coupling. Copyright © 2009 Royal Meteorological Society