Apparent Vertical Propagation of the NAM Index Due to an Embedded Wave Structure

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概要

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• The leading empirical orthogonal function (EOF) of the geopotential height is called the Northern Annular Mode (NAM). Stratosphere-troposphere connections seen in the multilevel NAM signal are often considered as due to a propagation of the annular structure. However, the tropospheric leading EOF contains not just an annular structure, but also a wave structure. This indicates that the NAM index is sensitive to changes in wave activity. A previous study showed that an apparent downward propagation of the NAM index can appear as a result of a reflection of wave 1 due to a stratospheric sudden warming. If this result is correct, we may also expect to find a reverse case. Here we show a case when an amplification of a tropospheric wave 1 leads to a stratospheric warming, an apparent upward propagation of the "Annular" mode signal, i.e., change in the amplitude of the NAM index appears due to a projection on the wave component of the tropospheric NAM.

• 社団法人日本気象学会の論文
• 2007-12-25

著者

• Kodera Kunihiko

  Climate Research Department Meteorological Research Institute

• COUGHLIN Katie

  Department of the Meteorology, University of Reading

• Coughlin Katie

  Department Of The Meteorology University Of Reading

• COUGHLIN Katie

  Department of the Meteorology, University of Reading:(Present Office)Risk Management Solutions

関連論文

• Apparent Vertical Propagation of the NAM Index Due to an Embedded Wave Structure

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