Nocturnal vertical distribution of stratospheric O 3 , NO 2 and NO 3 from balloon measurements

Simultaneous measurements of NO 2 , O 3 , NO 3 , and aerosol extinction coefficient vertical distribution have been made in the middle of the night by the AMON (Absorption par Minoritaires Ozone et No x ) 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 NO 2 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 NO 3 concentration at 38 km could be explained by an occasionally steep vertical gradient of temperature concentrations, another increase of both NO 2 and NO 3 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.