The Coupling of Dynamics and Chemistry in the Antarctic Stratosphere
PhD Student: Petra Huck
Joint Supervisor: Greg Bodeker (NIWA, Lauder)
Trends and variability in global ozone have important
consequences for life on Earth. Without the protection of stratospheric ozone,
life-threatening surface ultraviolet irradiation would increase. This has
important consequences for the biosphere, human health and economic
sustainability.
Since the discovery of the Antarctic ozone hole in 1985
the severity and the size of the ozone hole have increased steadily. The
increase has not been monotonic however, and there are significant inter-annual
differences which are suggested to be strongly linked to mid-latitude planetary
wave activity.
Inter-annual differences in the severity of Antarctic
ozone depletion are anti-correlated with Southern Hemisphere mid-latitude
planetary wave activity, as has been shown by analyses based on measurements and
modelling. There are a number of mechanisms whereby changes in wave activity
affect the Antarctic stratosphere, viz.:
1)
Waves may affect the total column ozone distribution directly through
meridional and vertical transport of ozone;
2)
During the winter, heat transport induced by upward propagating planetary
waves warms the vortex which reduces the occurrence of polar stratospheric
clouds (PSCs) on which heterogeneous chemical reactions lead to ozone
destruction.
3)
Planetary waves can displace the vortex off the pole (wave 1), or
elongate the vortex (wave 2), which influences NOx chemistry.
4)
Planetary waves can change the size of the Antarctic vortex, influence
the isolation of the vortex from mid-latitudes, and affect the longevity of the
polar vortex.
This project aims to further examine these effects on
Antarctic ozone depletion. Furthermore, models suggest that there is a delay
between anomalies in planetary activity and anomalous Antarctic ozone depletion
so that mid-winter planetary wave activity could be used to forecast Antarctic
ozone hole severity.