Dynamics of the Arctic Oscillation and the Process of the Low-Frequency Variability

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The Arctic Oscillation draws increasingly more attention in recent years in association with abnormal weather and global change problems. In the first year of 2006, the first workshop on the Arctic Oscillation Study was held during 7-8 July 2006 at the University of Tsukuba. About 30 participants gathered to present the latest scientific results and to discuss on the subject. The head investigator organized the 7th International Conference of the Global Change: Connection to the Arctic (GCCA-7) at the University of Alaska Fairbanks for 19-20 February 2007 and presented the review of the Arctic Oscillation study. The second workshop on the Arctic Oscillation Study was held during 2-3 March 2007 at the University of Tsukuba. About 40 participants gathered to present the latest scientific results and to discuss on the subject. In the second year of 2007, the bead investigator organized the first union session of the Sciences in the Arctic during the Japan Geosciences Union Meeting 2007 wi … More th a special topic of the Arctic Oscillation. The union session is upgraded to the regular session in 2008. The contributions from the Arctic Oscillation Studies were summarized as the Special Edition of the Journal of the Meteorological Society of Japan in December 2007 issue. In the Special Edition, 12 refereed papers on the subject of the Arctic Oscillation were published.According to the summary of these papers, we have reached to the conclusion that the Arctic Oscillation can be understood as a dynamical singular eigenmode of the global atmosphere. The singular eigenmode has a unique property of zero eigenvalue with a structure identical to the Arctic Oscillation so that it can respond resonantly to arbitrary quasi-steady barotropic forcing. However, the quasi-steady forcing from the storm tracks at the Pacific and Atlantic sectors acts independently with large amplitudes, so the Arctic Oscillation apperas as if it is a statistical artifact of the EOF analysis, recognizing only the teleconnections of NAO in the Atlantic sector and PNA in the Pacific sector. Less