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Ozone and Atmospheric Transport

Ozone has been studied since the 1930s, in large part because of its properties as a tracer of atmospheric motion. Although recent interest in ozone focuses on its importance as an absorber of UV and IR radiation (and thereby an important greenhouse gas), and as a tropospheric oxidant and pollutant, the relatively long chemical lifetime of ozone in both the stratosphere and the troposphere means that transport is as important as chemistry to understanding the past and present, and predicting the future distribution of ozone in the atmosphere.

In Canada routine measurements of the vertical profile of ozone concentration using balloon-borne ozonesondes have been carried at Resolute Bay since 1966, making this record the longest in the world.  Ozonesondes are currently flown weekly at eight sites, making the Canadian network also one of the largest in the world, and particularly important for studies of ozone changes over the past half-century.

Since its early use in the 1970s, atmospheric Lagrangian transport (trajectory) modeling, driven by increasingly sophisticated and accurate numerical weather prediction models, has become a powerful tool for studying the transport of atmospheric tracers like ozone. Although these data are sparse both in space and time, they have high vertical resolution, and can be extended by trajectory mapping to other locations and times. This is possible because the lifetime of ozone is of the order of weeks in the troposphere, and months or more in the stratosphere. This widely available technique has numerous applications to the study of ozone processes, and has been essential to current understanding of Arctic ozone depletion, and stratosphere-troposphere exchange. Recent uses of trajectory mapping in ozone data assimilation and in ozone source attribution will also be shown.

A recent application of trajectory mapping to the entire global ozonesonde dataset has produced a unique three-dimensional global ozone dataset from the late 1960s to the present day.  Although developed initially as climatology for use as an a priori for models and for satellite retrievals, the dataset can also be used for the study of regional and global ozone trends, stratosphere-troposphere relationships, and the regional representativeness of individual sounding sites.