Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Physics

Supervisor

Dr. Wayne Hocking

2nd Supervisor

Dr. David Tarasick

Joint Supervisor

Abstract

Ozone intrusions from the stratosphere to the troposphere occur as part of the Brewer-Dobson circulation, but the details of the microphysics of the process are unresolved. This research mainly focuses on near-tropopause regions, and examines stratospheric ozone intrusions into the troposphere across this stable zone. My research objective is to identify the small-scale atmospheric dynamical features responsible for the intrusion of stratospheric ozone into the troposphere, and to determine their relative importance from case to case.

Windprofiler radars, together with frequent ozonesonde launches, have been used to detect stratospheric ozone intrusions. This work has been supplemented by numerical simulation via GEM-FLEXPART to unambiguously confirm the leakage. We have identified stratospheric ozone intrusion occurrence at the measurement site, and/or in some cases at some distance from the measurement site. In the latter case, ozone reaches the radar site after being blown horizontally with the wind. We have diagnosed radar measurements of the standard deviation of the vertical wind, vertical shear of the horizontal wind, and turbulence strengths, as possible indicators of small-scale atmospheric activity. Increases in the standard deviation of the vertical wind are considered to indicate enhanced gravity wave activity, and enhancements in wind shear are taken to indicate increases in small-scale dynamics (including gravity wave activity).

The study shows frequent strong correlation between intrusion events and strong atmospheric activity. The atmospheric dynamics responsible for the intrusion of stratospheric ozone varies from case to case. On the one hand, we see that all parameters can act simultaneously, which clearly amplifies the intrusions. On the other hand, we see either one or any combination of the parameters acting to cause intrusions. However, the Eureka 2008 and Montreal 2005 (on 9th May) campaigns are exceptional cases where we do not see any strong atmospheric activity.

We have also modeled atmospheric diffusion and examined the differences due to homogeneous turbulence compared with turbulence that is spatially and temporally intermittent.

This unique combination of observational and numerical modeling helps detect the sources and sinks of ozone-related atmospheric pollutants that have negative impact on air quality, climate change and ozone depletion.

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