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The Photochemistry of Ozone Loss in the Arctic Region In Summer (POLARIS) is the latest in a series of high-altitude airborne investigations of atmospheric ozone spanning more than a decade. The objective of POLARIS is to understand the behavior of polar stratospheric ozone as it changes from very high concentrations in spring down to very low concentrations in autumn.

Ozone is an important component of our atmosphere; it screens the Earth from the biologically harmful effects of solar ultraviolet radiation. Because of the role ozone plays, we must have a clear understanding of the distribution, chemistry, and physics of stratospheric ozone that will allow us to determine whether various atmospheric changes such as those related to aircraft emissions or the release of chlorofluorocarbons might be causing stratospheric ozone changes.

The Arctic is a unique region for stratospheric ozone research. First, stratospheric temperatures are quite low during the winter polar night, enabling a variety of chemical reactions to occur on surfaces of particles which comprise polar stratospheric clouds. Second, the continuous daylight conditions of the polar summer enable a much different chemical environment than is observed at similar times in mid-latitude regions.

Campaigns similar to POLARIS have been conducted from bases all over the world, including Punta Arenas, Chile; Christchurch, New Zealand; Barbers Point, Hawaii; Moffett Field, California; Bangor, Maine; Stavanger, Norway; and Fairbanks, Alaska. This broad range of operational bases provided the latitudinal coverage required for the atmospheric studies being conducted.

Previous ER-2 aircraft missions have focused on understanding ozone loss in the polar regions and mid-latitudes of both hemispheres; atmospheric transport between the polar regions, mid-latitudes, and tropics, as well as between the troposphere and stratosphere; and the relative importance of various chemical cycles for ozone production and loss. The scientific data obtained on these missions have been used extensively in international assessments of stratospheric ozone depletion. These assessment documents represent the scientific basis for actions under the United Nations Montreal Protocol, which provides for the control of ozone-depleting chemicals. In a similar manner, results from the POLARIS mission will contribute to an assessment of the atmospheric effects of aviation emissions of gases and particles.