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The extratropical 40-day oscillation in the UCLA general circulation model. Part 1: Atmospheric angular momentumVariations in atmospheric angular momentum (AAM) are examined in a three-year simulation of the large-scale atmosphere with perpetual January forcing. The simulation is performed with a version of the University of California at Los Angeles (UCLA) general circulation model that contains no tropical Madden-Julian Oscillation (MJO). In addition, the results of three shorter experiments with no topography are analyzed. The three-year standard topography run contains no significant intraseasonal AAM periodicity in the tropics, consistent with the lack of the MJO, but produces a robust, 42-day AAM oscillation in the Northern Hemisphere (NH) extratropics. The model tropics undergoes a barotropic, zonally symmetric oscillation, driven by an exchange of mass with the NH extratropics. No intraseasonal periodicity is found in the average tropical latent heating field, indicating that the model oscillation is dynamically rather than thermodynamically driven. The no-mountain runs fail to produce an intraseasonal AAM oscillation, consistent with a topographic origin for the NH extratropical oscillation in the standard model. The spatial patterns of the oscillation in the 500-mb height field, and the relationship of the extratropical oscillation to intraseasonal variations in the tropics, will be discussed in Part 2 of this study.
Document ID
19950028636
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Marcus, S. L.
(Jet Propulsion Laboratory, Pasadena, CA United States)
Ghil, M.
(Univ. of California, Los Angeles, CA United States)
Dickey, J. O.
(Jet Propulsion Laboratory, Pasadena, CA United States)
Date Acquired
August 16, 2013
Publication Date
June 1, 1994
Publication Information
Publication: Journal of the Atmospheric Sciences
Volume: 51
Issue: 11
ISSN: 0022-4928
Subject Category
Meteorology And Climatology
Accession Number
95A60235
Funding Number(s)
CONTRACT_GRANT: NSF-ATM90-13217
CONTRACT_GRANT: NAG5-317
Distribution Limits
Public
Copyright
Other

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