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Climatology of the stratospheric polar vortex and planetary wave breakingThe distribution of Ertel's potential vorticity (PV) on the 850 K isentropic surface is used to establish a climatology for the transient evolution of the planetary scale circulation in the Northern Hemisphere winter midstratosphere. PV distributions are computed from gridded NMC daily temperature and height maps for the 10 and 30 mb levels, and show that a very good approximation for 850 K PV can be derived from 10 mb heights and temperatures alone. It is assumed that reversals of the latitudinal gradient of PV, localized in longitude and latitude may be regarded as signatures of planetary wave breaking. Wave breaking identified by such signatures tends to occur mainly in the vicinity of the Aleutian anticyclone, with a secondary maximum over Europe. The area of the polar vortex, defined as the area enclosed by PV contours greater than a certain critical value, is strongly influenced by wave breaking. Erosion of the polar vortex due to transport and mixing of PV leads to a preconditioned state, when defined in terms of vortex area, that always occurs prior to major stratospheric warmings. During winters with little PV transport or mixing, the vortex area evolves rather uniformly in response to radiative forcing. During winters with major sudden warmings, the wave breaking signature as defined here first appears at low values of PV, then rapidly moves toward higher values as the vortex area is reduced and the 'surf-zone' structure becomes well defined.
Document ID
19880052059
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Baldwin, Mark P.
(Washington Univ. Seattle, WA, United States)
Holton, James R.
(Washington, University Seattle, United States)
Date Acquired
August 13, 2013
Publication Date
April 1, 1988
Publication Information
Publication: Journal of the Atmospheric Sciences
Volume: 45
ISSN: 0022-4928
Subject Category
Geophysics
Accession Number
88A39286
Funding Number(s)
CONTRACT_GRANT: NAGW-662
CONTRACT_GRANT: NSF ATM-83-14111
Distribution Limits
Public
Copyright
Other

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