Ozone-depletion studies

Ground-based and in situ monitoring of polar stratospheric clouds. Alberto Adriani, Institute of Atmospheric Physics, Rome, Italy. In cooperation with the U.S. Antarctic Program and in collaboration with the University of Wyoming, Italian scientists will make laboratory-based light radar (lidar) observations and in situ measurements by laser backscatter sondes of polar stratospheric clouds (PSCs) above McMurdo Station. These data add to the available information concerning the annual springtime depletion of ozone in the antarctic stratosphere and enhance scientific understanding of the role of PSCs in the depletion process. The lidar observations are also in the frame of the Network for the Detection of Stratospheric Change activity. (S-107)

In situ measurements of polar stratospheric clouds (PSCs) spanning the austral winter and of ozone from late winter to early spring. Terry Deshler, University of Wyoming. The annual stratospheric ozone hole above Antarctica is driven by chlorine compounds that interact on the surfaces of polar stratospheric clouds, which form during the polar winter. It is for this reason that the hole appears in the austral spring and that ozone depletion is much more severe in polar regions than elsewhere. By using balloonborne instruments, this investigation provides detailed information on the actual cloud particles and the distribution of the clouds and the ozone. The measurements will provide vertical profiles of both the PSCs and ozone, size distributions of the PSC particles, and some information on their composition and physical state (liquid or solid). The project is enhanced by cooperation with an Italian investigator who operates a lidar system at McMurdo Station. The project contributes to the World Meteorological Organization/UNEP Network for the Detection of Stratospheric Change and the Global Change Initiative. (S-131)

Measurement of stratospheric chlorine monoxide and other trace gases over McMurdo Station in the austral spring. Robert deZafra, State University of New York. Chlorine monoxide (ClO) is a product of the destruction of stratospheric ozone by chlorine, which is present in the stratosphere as a result of the breakdown of chlorofluorocarbons (CFCs). ClO, as well as other trace stratospheric gases that are important in the antarctic ozone hole, can be measured from the ground by microwave receivers, similar to those used in radio astronomy. This project will continue a decade-long series of such measurements to extend the climatology, but more important, to provide as well a cross calibration of a new Network for the Detection of Stratospheric Change (NDSC) ClO microwave instrument, which has recently been installed nearby at New Zealand's Scott Base. The NDSC instruments are being installed at a number of sites worldwide as part of a joint National Aeronautics and Space Administration/World Meteorological Organization/UNEP program, and it is quite important to provide as much correlative information as possible so that the NDSC can be relied upon in the future to monitor the health of the stratosphere. (S-137)

Trace gas measurements over the South Pole using millimeter-wave spectroscopy. Robert deZafra, State University of New York. Many atmospheric gases radiate energy in the millimeter wavelength region of the radio spectrum; each species has a unique spectrum. The shape of each individual species' spectrum provides information on the temperature and pressure of the gas; thus, one can use the millimeter-wave spectrum of the atmosphere to determine the relative abundances and height distribution of a number of trace species. In this particular investigation, millimeter spectroscopy will be used to monitor ozone, carbon monoxide, nitrous oxide, nitric acid, water vapor, and nitrogen dioxide above South Pole over the period of year. Several of these gases play important roles in the formation of the annual antarctic ozone hole, whereas others, particularly water vapor and carbon monoxide, can provide information of the dynamics, particularly vertical transport, of the upper stratosphere and mesosphere. ( S-138)