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Simulations of Dynamics and Transport during the September 2002 Antarctic Major WarmingA mechanistic model simulation initialized on 14 September 2002, forced by 100-hPa geopotential heights from Met Office analyses, reproduced the dynamical features of the 2002 Antarctic major warming. The vortex split on approx.25 September; recovery after the warming, westward and equatorward tilting vortices, and strong baroclinic zones in temperature associated with a dipole pattern of upward and downward vertical velocities were all captured in the simulation. Model results and analyses show a pattern of strong upward wave propagation throughout the warming, with zonal wind deceleration throughout the stratosphere at high latitudes before the vortex split, continuing in the middle and upper stratosphere and spreading to lower latitudes after the split. Three-dimensional Eliassen-Palm fluxes show the largest upward and poleward wave propagation in the 0(deg)-90(deg)E sector prior to the vortex split (coincident with the location of strongest cyclogenesis at the model's lower boundary), with an additional region of strong upward propagation developing near 180(deg)-270(deg)E. These characteristics are similar to those of Arctic wave-2 major warmings, except that during this warming, the vortex did not split below approx.600 K. The effects of poleward transport and mixing dominate modeled trace gas evolution through most of the mid- to high-latitude stratosphere, with a core region in the lower-stratospheric vortex where enhanced descent dominates and the vortex remains isolated. Strongly tilted vortices led to low-latitude air overlying vortex air, resulting in highly unusual trace gas profiles. Simulations driven with several meteorological datasets reproduced the major warming, but in others, stronger latitudinal gradients at high latitudes at the model boundary resulted in simulations without a complete vortex split in the midstratosphere. Numerous tests indicate very high sensitivity to the boundary fields, especially the wave-2 amplitude. Major warmings occurred for initial fields with stronger winds and larger vortices, but not smaller vortices, consistent with the initiation of wind-deceleration by upward-propagating waves near the poleward edge of the region where wave 2 can propagate above the jet core. Thus, given the observed 100-hPa boundary forcing, stratospheric preconditioning is not needed to reproduce a major warming similar to that observed. The anomalously strong forcing in the lower stratosphere can be viewed as the primary direct cause of the major warming.
Document ID
20070025103
Acquisition Source
Jet Propulsion Laboratory
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Manney, Gloria L.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Sabutis, Joseph L.
(New Mexico Highlands Univ. Las Vegas, NM, United States)
Allen, Douglas R.
(Naval Research Lab. Washington, DC, United States)
Lahoz, Willian A.
(Reading Univ. United Kingdom)
Scaife, Adam A.
(Meteorological Office United Kingdom)
Randall, Cora E.
(Colorado Univ. Boulder, CO, United States)
Pawson, Steven
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Naujokat, Barbara
(Freie Univ. Berlin, Germany)
Swinbank, Richard
(Meteorological Office United Kingdom)
Date Acquired
August 23, 2013
Publication Date
March 1, 2005
Publication Information
Publication: Journal of Atmospheric Sciences
Volume: 62
Issue: 3
Subject Category
Meteorology And Climatology
Distribution Limits
Public
Copyright
Other
Keywords
Antartica
winds
warming

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