Measurements Addressing the Initial Stages of Ozone Recovery, the Nucleation of, Index of Refraction of, and Existence of Large PSC Particles

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In the past twenty years there has been a rather rapid decline in Antarctic stratosphere ozone in the spring, which is due directly to halogens released into the atmosphere since the 1930s. This proposal seeks support for continuing in situ balloon-borne ozonesonde measurements over McMurdo through 2008. These measurements, begun in 1986, documented the decline and minimum in stratospheric ozone observed as chlorine increased and reached its maximum. Now the emphasis is shifting to observing the first signs of the ozone recovery. The ozonesondes are uniquely capable of observing in the altitude range where ozone suffers the greatest chemical loss, and thus they are able to separate chemical and transport effects. These instruments may be among the first to establish the ozone benefits resulting from declining chlorine. In 2007, it is proposed to collaborate with European colleagues in a second international Antarctic campaign to test the 3-D chemical transport models of ozone loss; this campaign will occur as part of the Intentional Polar Year activities and will consist of a second year of winter/spring ozone measurements from McMurdo. Another important aspect of the study is observations of the Polar Stratospheric Clouds (PSC) in the Antarctic, which will be continued to address questions related to the nucleation of nitric acid hydrates, the existence of large particles within Antarctic PSCs, and the index of refraction of PSC particles. Measurements to address questions related to nucleation of nitric acid hydrates within PSCs will include collaboration with the European VORCORE project. Thus, the main intellectual merit of this work lies in obtaining and analyzing measurements that may lead to the first signs of ozone recovery. The broader impacts of this work have several aspects. Measurements establishing the first signs of ozone recovery are important reassurances to the world community in support of the commercial sacrifices that have been made to limit the release of chlorine into the atmosphere. Thus, in addition to the scientific interest, there are broad social implications dependent on maintaining ozone measurements through the first decade after maximum chlorine has been reached in the stratosphere. This research also contributes to the training and education of a post-doctoral scholar, engineer, technician, and graduate students.