Ozone trends are observed in satellite and ground-based records in northern middle and high latitudes. Periods of perturbed stratospheric chemistry have been identified in the Arctic stratosphere and ozone losses can be partially attributed to the perturbed halogen chemistry. However, important issues in stratospheric chemistry and physics remain far from being clear. The Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME) has been proposed to tackle outstanding problems in stratospheric ozone research. This proposal is to perform a series of observations to contribute to some primary objectives of SESAME, in particular: to study in detail the NOy Partitioning, its characteristics in middle and high northern latitudes and its evolution throughout the polar winter; to study the evolution of denoxification and
denitrification by frequent profile measurements of NO2 and HNO3; to study the chemistry associated with lee-wave PSCs by measurements of O3, NO2, OClO, H2O and aerosol across the Norwegian mountains; to investigate the impact of chemically perturbed airmasses on mid-latitude chemistry in disturbed vortex conditions by measurements of O3, NO2, NO3 and OClO in mid-latitudes in spring; to identify periods of chlorine activation and the decay of active chlorine in spring, by measurements of ClONO2 and OClO; and to simulate the measurements by using box model calculations on isentropic trajectories and complementary 3-D model runs. The proposed activities focus on balloon-borne measurements using different in-situ and remote sensing instruments suitable to cover the components of the NOy family. A series of 'snapshot' measurements with large complex instruments or instrument packages will be performed to enable detailed case studies, particularly during winter 1994/1995. The snapshot measurements will be nested into regular 'climatological' observations of O3, NO2, OClO and aerosol optical depth using lightweight instruments. In addition, the utilization of PERSEUS is proposed for a few lightweight instruments capable of measuring NOy components. It is expected that the results of the proposed work - in combination with those obtained from other SESAME projects - will contribute to an improved understanding of stratospheric ozone in high and middle northern latitudes.
Funding SchemeCSC - Cost-sharing contracts