文档介绍：1FEBRUARY 2007 CHARLTON AND POLVANI 449
A New Look at Stratospheric Sudden Warmings. Part I: Climatology and
Modeling Benchmarks
ANDREW J. CHARLTON*
Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York
LORENZO M. POLVANI
Department of Applied Physics and Applied Mathematics, and Department of Earth and Environmental Sciences,
Columbia University, New York, New York
(Manuscript received 13 October 2005, in final form 28 March 2006)
ABSTRACT
Stratospheric sudden warmings are the clearest and strongest manifestation of dynamical coupling in the
stratosphere–troposphere system. While many sudden warmings have been individually documented in the
literature, this study aims at constructing prehensive climatology: all major midwinter warming events
are identified and classified, in both the NCEP–NCAR and 40-yr ECMWF Re-Analysis (ERA-40) datasets.
To plish this a new, objective identification algorithm is developed. This algorithm identifies sudden
warmings based on the zonal mean zonal wind at 60°N and 10 hPa, and classifies them into events that do
and do not split the stratospheric polar vortex.
Major midwinter stratospheric sudden warmings are found to occur with a frequency of approximately six
events per decade, and 46% of warming events lead to a splitting of the stratospheric polar vortex. The
dynamics of vortex splitting events is contrasted to that of events where the vortex is merely displaced off
the pole. In the stratosphere, the two types of events are found to be dynamically distinct: vortex splitting
events occur after a clear preconditioning of the polar vortex, and their influence on middle-stratospheric
temperatures lasts for up to 20 days longer than vortex displacement events. In contrast, the influence of
sudden warmings on the tropospheric state is found to be largely insensitive to the event type.
Finally, a table of dynamical benchmarks for major stratospheric