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Role of atmospheric waves in the formation and maintenance of the Northern Annular Mode
Author(s) -
Kuroda Yuhji,
Mukougawa Hitoshi
Publication year - 2013
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/jgrd.50709
Subject(s) - atmospheric wave , climatology , eddy , northern hemisphere , synoptic scale meteorology , mode (computer interface) , momentum transfer , atmospheric sciences , momentum (technical analysis) , environmental science , geology , meteorology , gravity wave , wave propagation , physics , turbulence , scattering , optics , finance , computer science , economics , operating system
We examined the roles of stationary, synoptic, and medium‐scale atmospheric waves in the formation and maintenance of the Northern Annular Mode (NAM) in winter by analyses of zonal momentum and wave energy based on six‐hourly reanalysis data from the European Centre for Medium‐range Weather Forecasts (ECMWF ERA‐Interim). Medium‐scale waves have periods shorter than about two days and their effect has been overlooked in previous research on the NAM. The effect of medium‐scale waves on the NAM is about 10% of that of total eddies. Although their effect on the NAM is of less importance than their effect on the Southern Annular Mode (SAM), it is still significant in the Northern Hemisphere. Our analysis also suggests that synoptic, medium‐scale, and stationary waves provide positive feedback to the zonal‐mean zonal wind of the NAM. In particular, energy transfer from synoptic and low‐frequency transient waves to stationary waves plays a key role in sustaining the stationary waves that drive zonal winds associated with the NAM.