The first, long-term, in situ measurement of ozone depletion in the Antarctic ozone hole

The discovery of an annual, austral spring decrease in column abundances of ozone over the Antarctic continent, now popularly known as the “ozone hole”, has served as a bellwether for the impact of anthropogenic emissions on the global atmosphere. While the overall chemistry responsible for the ozone hole has been identified with certainty, the exact details of the chemical and dynamic mechanisms are still unresolved and the ability of chemical models to reproduce the fine scale structure of the ozone less is mixed. The primary data sets with which to explore the details of Antarctic ozone loss have been limited largely to satellite observations and a single season (2003) of coordinated ozonesonde launches following the Match technique. Longer term, in situ, chemical measurements will significantly increase our understanding of the specific mechanisms responsible for stratospheric ozone loss, and improve our ability to model and forecast the anticipated recovery of the ozone hole.

We will present preliminary results from the first in situ ozone measurements during the formation of the Antarctica ozone hole. Three solid-state ozone photometers are being flown on long duration super pressure balloons as part of the international Concordiasi project. The super pressure balloons will follow an isopycnal trajectory and will provide a near-Lagrangian measurement platform in the polar vortex. The balloons will be launched from McMurdo Station, Antarctica, in early September and will maintain altitudes in the range of 16 – 20km. Ozone measurements will be taken at a cadence ranging from 15 minutes to 1 hour depending on the power availability and the rate of change of ozone. The ozone instrument and balloon platform is expected to have a 3 to 6 month lifetime and provide in situ measurements of both the formation and breakup of the Antarctic ozone hole. Barring technical mishaps, flights will continue until the balloons leave the Antarctic region during the collapse of the polar vortex. In addition to the ozone sensors, the balloons are carrying meteorological instruments and optical particle counters for the identification of polar stratospheric clouds. Launches of ozone sondes timed with overpasses of the long duration balloon from several participating Antarctic bases will provide verification and calibration of the long duration balloon borne instruments. A focus of the study will be the determination of ozone depletion rates, particularly in the presence of polar stratospheric clouds. This data set will be valuable for addressing some of the outstanding questions about stratospheric ozone depletion soon after polar sunrise and for constraining photochemical models that are used to predict the future state of stratospheric ozone.