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A New Look at Stratospheric Sudden Warmings. Part II: Evaluation of Numerical Model SimulationsThe simulation of major midwinter stratospheric sudden warmings (SSWs) in six stratosphere-resolving general circulation models (GCMs) is examined. The GCMs are compared to a new climatology of SSWs, based on the dynamical characteristics of the events. First, the number, type, and temporal distribution of SSW events are evaluated. Most of the models show a lower frequency of SSW events than the climatology, which has a mean frequency of 6.0 SSWs per decade. Statistical tests show that three of the six models produce significantly fewer SSWs than the climatology, between 1.0 and 2.6 SSWs per decade. Second, four process-based diagnostics are calculated for all of the SSW events in each model. It is found that SSWs in the GCMs compare favorably with dynamical benchmarks for SSW established in the first part of the study. These results indicate that GCMs are capable of quite accurately simulating the dynamics required to produce SSWs, but with lower frequency than the climatology. Further dynamical diagnostics hint that, in at least one case, this is due to a lack of meridional heat flux in the lower stratosphere. Even though the SSWs simulated by most GCMs are dynamically realistic when compared to the NCEP-NCAR reanalysis, the reasons for the relative paucity of SSWs in GCMs remains an important and open question.
Document ID
20070034806
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Charlton, Andrew J.
(Columbia Univ. New York, NY, United States)
Polvani, Lorenza M.
(Columbia Univ. New York, NY, United States)
Perlwitz, Judith
(Colorado Univ. Boulder, CO, United States)
Sassi, Fabrizio
(National Center for Atmospheric Research Boulder, CO, United States)
Manzini, Elisa
(Istituto Nazionale di Geofisica e Vulcanologia Bologna, Italy)
Shibata, Kiyotaka
(Meteorological Research Inst. Tokyo, Japan)
Pawson, Steven
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Nielsen, J. Eric
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Rind, David
(NASA Goddard Inst. for Space Studies New York, NY, United States)
Date Acquired
August 24, 2013
Publication Date
February 1, 2007
Publication Information
Publication: Journal of Climate
Volume: 20
Issue: 3
Subject Category
Meteorology And Climatology
Funding Number(s)
CONTRACT_GRANT: NNX06AC95G
Distribution Limits
Public
Copyright
Other

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