Observed Changes in the Southern Hemispheric Circulation in May
Name
Observed changes in the southern.pdf
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2.22 MB
Format
Adobe PDF
Checksum (MD5)
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Author(s)
Hilgenbrink, Casey
Kinnison, Doug
Alan Plumb, R.
Sheshadri, Aditi
Thompson, David W. J.
Ivy, Diane J
Solomon, Susan
Date Issued
December 2016
Journal
Journal of Climate
Publisher
American Meteorological Society
Citation
Ivy, Diane J. et al. “Observed Changes in the Southern Hemispheric Circulation in May.” Journal of Climate 30, 2 (January 2017): 527–536 © 2017 American Meteorological Society
Version
Final published version
Abstract
Much research has focused on trends in the Southern Hemispheric circulation in austral summer (December–February) in the troposphere and stratosphere, whereas changes in other seasons have received less attention. Here the seasonality and structure of observed changes in tropospheric and stratospheric winds, temperature, and ozone over the Southern Hemisphere are examined. It is found that statistically significant trends similar to those of the Antarctic summer season are also observed since 1979 in austral fall, particularly May, and are strongest over the Pacific sector of the hemisphere. Evidence is provided for a significant shift in the position of the jet in May over the Pacific, and it is shown that the strengthening and shifting of the jet has rendered the latitudinal distribution of upper-tropospheric zonal wind more bimodal. The Antarctic ozone hole has cooled the lower stratosphere and strengthened the polar vortex. While the mechanism and timing are not fully understood, the ozone hole has been identified as a key driver of the summer season tropospheric circulation changes in several previous observational and modeling studies. It is found here that significant ozone depletion and associated polar cooling also occur in the lowermost stratosphere and tropopause region through austral fall, with spatial patterns that are coincident with the observed changes in stratospheric circulation. It is also shown that radiatively driven temperature changes associated with the observed ozone depletion in May represent a substantial portion of the observed May cooling in the lowermost stratosphere, suggesting a potential for contribution to the circulation changes.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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DOI of Published Version
https://doi.org/10.1175/jcli-d-16-0394.1
