ODD OXYGEN MEASUREMENTS DURING THE NOCTILUCENT-CLOUD-93 ROCKET CAMPAIGN

The NLC-93 campaign at Esrange, Sweden, addressed the chemical, dynami cal and electrical environment of the summer mesopause in the presence of noctilucent clouds (NLC). A major topic was the detailed investiga tion of odd oxygen abundances and their structure in the vicinity of t he cloud layer. Applying independent in situ measurements, we have obt ained consistent profiles of atomic oxygen, ozone, and mesospheric tot al density. Atomic oxygen was measured on two rocket flights by means of a newly developed probe utilizing the 1304 Angstrom resonance fluor escence / absorption technique. Detailed Monte Carlo simulations of th e radiative transfer and the instrument aerodynamics are included in t he data analysis. We find relatively low atomic oxygen densities with a peak of 2 x 10(11) cm(-3) at 96 km. An airglow radiometer recorded t he O-2 IR-atmospheric band emission, allowing the retrieval of ozone d ensities by means of an inversion model that considers both direct and indirect sources of O-2 (a(1)Delta(g)). The odd oxygen measurements a re compared to a steady state photochemical model. While good agreemen t is found in the mesosphere, the results deviate close to the cold me sopause. Significant vertical structures are found in the atomic oxyge n profiles; sharp gradients and distinct minima coincide with the obse rved NLC layer. Possible influences of heterogeneous chemistry on the odd oxygen abundance are discussed.