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GCM simulations of intraseasonal variability in the Pacific/North American regionGeneral circulation model (GCM) simulations of low-frequency variability with time scales of 20 to 70 days are analyzed for the Pacific sector during boreal winter. The GCM's leading mode in the upper-tropospheric zonal wind is associated with fluctuations of the East Asian jet; this mode resembles, in both structure and amplitude, the Pacific/North American (PNA) pattern found in the observations on these time scales. In both the model and observations, the PNA anomaly is characterized by: (1) a linear balance in the upper-tropospheric vorticity budget with no significant Rossby wave source in the tropics, (2) a barotropic conversion of kinetic energy from the time mean Pacific jet, and (3) a north/south displacement of the Pacific storm track. In the GCM, the latter is associated with synoptic eddy heat flux and latent heat anomalies that appear to contribute to a strong lower-tropospheric source of wave activity over the North Pacific. This is in contrast to the observations, which show only a weak source of wave activity in this region.
Document ID
Document Type
Reprint (Version printed in journal)
Schubert, Siegfried
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Suarez, Max
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Park, Chung-Kyu
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Moorthi, Shrinivas
(Univ. Space Research Association; NASA, Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 16, 2013
Publication Date
July 1, 1993
Publication Information
Publication: Journal of the Atmospheric Sciences
Volume: 50
Issue: 13
ISSN: 0022-4928
Subject Category
Meteorology And Climatology
Accession Number
Funding Number(s)
PROJECT: RTOP 578-41-07-20
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