Zonal—eddy coupling and a neutral mode theory for the Arctic Oscillation

Kimoto, Masahide; Jin, Fei‐Fei; Watanabe, Masahiro; Yasutomi, Natsuko

doi:10.1029/2000gl012377

Cited by 62 publications

(65 citation statements)

References 23 publications

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“…Thus, how the seesaw influences the stratospheric circulation differs fundamentally from how the AO (or Northern Hemisphere annular mode) does so. The primary process in the latter is the interaction between the anomalous polar vortex and modulated propagation of planetary waves (Kuroda and Kodera 1999;Thompson and Wallace 2000;Hartmann et al 2000;Kimoto et al 2001). Superposition of the three-dimensional anomalies associated with the AL-IL seesaw upon the climatological-mean circulation leads to significant modifications in the pattern of planetary waves and accordingly in their upward and horizontal propagation.…”

Section: Discussionmentioning

confidence: 99%

Interannual Seesaw between the Aleutian and Icelandic Lows. Part III: Its Influence upon the Stratospheric Variability.

Nakamura

Honda

2002

Journal of the Meteorological Society of Japan

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Three-dimensional structure of quasi-stationary circulation anomalies observed in the course of a typical life cycle of an interannual seesaw between the surface Aleutian and Icelandic lows (AL and IL, respectively) is examined by using a reanalysis data set for the last three decades. A diagnosis is applied in a particular framework where the 31-day mean anomalies are regarded as stationary Rossby waves embedded in the zonally varying climatological-mean flow. It reveals that the upward propagation of wave activity into the stratosphere occurs in late winter primarily from the tropospheric anomalies corresponding to the anomalous IL, which develops below the entrance region of the lower-stratospheric polar night jet as a remote influence from the North Pacific. Accordingly, the North Atlantic anomalies exhibit apparent amplification and westward phase tilt with height, whereas the North Pacific anomalies are much more like the external mode. It appears that, in the presence of the zonal wavenumber 1 ðk ¼ 1Þ component of the climatological-mean planetary waves, the polar-night jet over the Pacific is shifted too far north to allow the stationary anomalies associated with the anomalous AL to propagate upward as stationary Rossby waves.Unlike the predominant signal of the Arctic Oscillation (or annular mode) that alters the intensity of the polar vortex, the seesaw modifies the stratospheric planetary-wave patterns in a modest but significant manner. In late winter when the AL is weaker than normal associated with a particular phase of the seesaw, the k ¼ 1 component is masked by the enhanced zonal wavenumber 2 (k ¼ 2) component embedded in the intensified polar-night jet. In contrast, the predominant k ¼ 1 component embedded in the relatively weak polar-night jet dominates over the diminished k ¼ 2 component in late winter, when the AL is stronger associated with the other phase of the seesaw. Our examination of seven late-winter major events of stratospheric sudden warming over the three recent decades suggests that the polarity of the AL-IL seesaw might set up a condition of which planetary wave component (k ¼ 1 or k ¼ 2) is more strongly involved in a late-winter warming event.

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Section: Discussionmentioning

confidence: 99%

Interannual Seesaw between the Aleutian and Icelandic Lows. Part III: Its Influence upon the Stratospheric Variability.

Nakamura

Honda

2002

Journal of the Meteorological Society of Japan

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“…[15] It is common for the zonal-mean zonal wind associated with the winter NAM to be maintained by interactions between zonal wind and waves, such as planetary-scale Rossby waves and baroclinic waves [e.g., Hartmann, 1999, 2000;Yamazaki and Shinya, 1999;Kimoto et al, 2001]. The wave and zonal-mean zonal wind interaction associated with the summer NAM is next demonstrated.…”

Section: Methodsmentioning

confidence: 99%

Abrupt evolution of the summer Northern Hemisphere annular mode and its association with blocking

et al. 2010

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Using reanalysis data from the National Centers for Environmental Prediction‐National Center for Atmosperic Research, Boulder, Colorado, for the period from 1958 to 2005, we statistically analyzed the relationships of the summer Northern Hemisphere annular mode (summer NAM) with hemispheric‐scale anomalous summer weather and the occurrence of blocking highs. The anomalous positive NAM (low‐pressure anomaly in the Arctic and high‐pressure anomaly in midlatitudes) accounts well for the hemispheric‐scale weather associated with anomalous blocking between the polar and subtropical jets, whereas blocking rarely occurs during negative NAM periods. The double jet stream structure is more evident during periods of anomalous positive NAM than during periods of negative NAM. The surface temperatures associated with the anomalous positive NAM clearly show Europe to be hot and East Asia to be cool, as was the case during the anomalous summer of 2003. The occurrence of a positive summer NAM is therefore consistent with the hemispheric‐scale anomalous summer weather associated with blocking in 2003. We investigated the abrupt evolution of atmospheric patterns and the geographic distribution of blocking highs associated with the development, maintenance, and decay periods of an anomalous positive NAM. During the development period, blocking tends to occur over Europe and the Atlantic Ocean, but no significant blocking signature is evident over eastern Eurasia. During the maintenance stage, blocking tends to occur in the Far East. During the decay stage, blocking over the Pacific region is obvious. This longitudinal migration of blocking phenomena may be used to predict the evolution through time of the NAM.

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“…Kimoto et al (2001) suggested that the AO is induced by the interactions with the forced steady planetary waves. In contrast, Tanaka (2003) suggested that the AO is induced by the interactions with the active transient eddies in the synoptic scale.…”

Section: Resultsmentioning

confidence: 99%

Energy Spectrum and Energy Flow of the Arctic Oscillation in the Phase Speed Domain

Tanaka

Terasaki

2005

SOLA

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In this study, energy spectrum and energy flow of the large-scale atmospheric motions are examined in reference to the Arctic Oscillation index. Attention is concentrated to the barotropic component of the atmosphere in the framework of the 3D normal mode decomposition.According to the result of the observational analysis in the phase speed domain, the Arctic Oscillation (AO) is characterized as the energy increase at the meridional index l=3 with simultaneous decrease at l=5 of the zonal field. The result is consistent with the theory of the AO by the singular eigenmode of the global atmosphere. The accumulation of energy at the eigenmode of the AO is explained by the enhanced energy flux FZi associated with the zonal-wave interaction.It is found in this study that the energy flux FZi comes from eddies at the spherical Rhines speed cR where the planetary-scale Rossby wave becomes stationary. The result suggests that the low-frequency variability associated with the AO is maintained by energy flux from cR, which is compensated by the up-scale energy cascade from synoptic eddies in addition to the forced stationary planetary waves by topography.

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Zonal—eddy coupling and a neutral mode theory for the Arctic Oscillation

Cited by 62 publications

References 23 publications

Interannual Seesaw between the Aleutian and Icelandic Lows. Part III: Its Influence upon the Stratospheric Variability.

Interannual Seesaw between the Aleutian and Icelandic Lows. Part III: Its Influence upon the Stratospheric Variability.

Abrupt evolution of the summer Northern Hemisphere annular mode and its association with blocking

Energy Spectrum and Energy Flow of the Arctic Oscillation in the Phase Speed Domain

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