HR: 0830h
AN: A31C-0045    [PDF]
TI: Multiple Planetary Flow Regimes and the Eddy Forcing in Northern Hemisphere Wintertime Variability
AU: * Wu, Q
EM: wuqig@cola.iges.org
AF: center for ocean-land-atmosphere studies, 4041 Powder Mill Road, suite 302, Calverton, MD 20805 United States
AU: Straus, D M
EM: straus@cola.iges.org
AF: center for ocean-land-atmosphere studies, George Mason University, 4041 Powder Mill Road, suite 302, Calverton, MD 20705 United States
AB: A cluster algorithm is applied to the zonal mean zonal wind from winter monthly means of the reanalyses of NCEP/NCAR. Four reproducible and robust clusters are found: two regimes represent the opposite phases the Northern Hemisphere Annular mode (NAM), and two regimes represent the opposite phases of a pattern which can be identified with the Cold Ocean-Warm Land (COWL) pattern. This identification is accomplished by regressing the zonal-mean zonal wind on the COWL-index derived from 500 hPa height data by Wu and Straus [2002]. Transformed Eulerian (or Eliassen-Palm) eddy forcing analysis is used to examine the maintenance of these clusters. The results show that barotropic forcing by the eddy momentum fluxes appears to maintain the wind anomalies in the upper troposphere and balances the Coriolis acceleration associated with the anomalous transformed mean meridional circulation, while the Coriolis acceleration maintains the wind anomalies against friction in the lower troposphere. This mechanism holds for both NAM-like and COWL-like regimes.
DE: 0399 General or miscellaneous
DE: 1610 Atmosphere (0315, 0325)
DE: 1620 Climate dynamics (3309)
DE: 5707 Atmospheres--structure and dynamics
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting