Recorded presentation5.6
Dynamical impacts of Antarctic stratospheric ozone depletion on the extratropical circulation of the Southern Hemisphere
Kevin M. Grise, Colorado State University, Fort Collins, CO; and D. W. J. Thompson
Southern Hemisphere springtime polar stratospheric zonal wind trends associated with the Antarctic ozone hole couple into the troposphere during December and January. Concurrent linear trends in both stratospheric and tropospheric variables are consistent with a delayed seasonal breakdown of the Southern Hemisphere stratospheric polar vortex and a positive tendency in the phase of the Southern Annular Mode (SAM). Decomposing these linear trends into a component linearly congruent with the SAM and its residual hints at the potential forcing mechanism behind the recent bias toward the positive phase of the SAM in the troposphere. Preliminary results indicate that this bias has a direct link with the diabatic cooling of the stratosphere associated with the Antarctic ozone hole and, in particular, the reduction of downwelling radiation near the tropopause. Overall, stratospheric linear trends in temperature are largest in November, but the temperature and downwelling longwave radiation trends near the tropopause strongly peak in December when the stratospheric zonal wind anomalies first couple to the troposphere. This dramatic decrease in downwelling longwave radiation at the tropopause may be essential to understanding the mechanism underlying stratospheric-tropospheric coupling.
Session 5, General Middle Atmosphere
Wednesday, 22 August 2007, 8:30 AM-12:10 PM, Multnomah
Previous paper Next paper