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Simultaneous measurements of NO2, O3, NO3, and aerosol extinction coefficient vertical distribution have been made in the middle of the night by the AMON (Absorption par Minoritaires Ozone et Nox) instrument on October 16, 1993, from a balloon platform at float altitude, above Aire sur l'Adour in the south of France. Amon measures atmospheric transmission in the UV Visible range, using the star occultation method. Vertical distributions, obtained between 20 and 40 km, are calculated by a tangent ray inversion technique. Measurements of NO and NO2 by the HALOE (HALogen Occultation Experiment) instrument aboard UARS were also available on October 17, 1993, close to Aire sur l'Adour. Comparison with box model simulations, including heterogeneous reactions, shows that while an increase of NO3 concentration at 38 km could be explained by an occasionally steep vertical gradient of temperature concentrations, another increase of both NO2 and NO3 measured by AMON between 22 to 25 km, i.e. in the upper part of the aerosol layer, cannot be explained by the model. Such an increase is also present on one HALOE profile close to Aire sur l'Adour, for the same altitude range.

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Five balloon‐borne observations of the vertical profile of stratospheric NO3 and ozone were performed between 1981 and 1985 by using the star and planet occultation technique at 662 nm. During the last two flights, NO2 was also measured by the same technique at 440 nm. The latest available laboratory determination of the 662‐nm absorption cross section of NO3 has been used for the data analysis. This gives NO3 concentrations that are about a factor of 2 lower than those previously reported. The concentration of NO3 increases with altitude, from about 1×107 molecules cm−3 around 22 km, to 2×107 molecules cm−3 at 38 km in September. A maximum value of 4×107 molecules cm−3 was observed at 38 km in May 1982. Ozone and NO2 results obtained from the same flights as NO3 are also presented. A companion paper provides details on the comparison between observed and modeled NO3 vertical profiles.

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