No abstract

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.

Simultaneous measurements of NO3 and O3 were performed at different periods of the night from stratospheric balloons launched from the CNES balloon station at Aire‐sur‐l'Adour in September 1980 and September 1981. The experimental NO3 vertical profiles compare favorably with those predicted by the photochemical theory. Differences can be explained by the dependence of the recombination rate of NO2 and O3 upon altitude. The O3 concentrations above 30 km measured by spectrophotometry around λ = 660 nm present a remarkable stability. Measurements obtained by means of this technique could be used as a reference for the detection of long‐term variations of O3.

The Solar Mesosphere Explorer (SME) satellite has observed the visible sunlight scattered at the earth's limb since early 1982. By using a radiative transfer model including multiple scattering and albedo effects, observations at 20°N latitude have been interpreted in terms of aerosol optical depth. The ratio of aerosol extinction to Rayleigh extinction at 431.8 nm shows a large increase after the eruption of El Chichon. A maximum ratio of 5 at 36 km and larger than 11 at 30 km occurs in the summer of 1982 followed by a decrease through 1983 and 1984. Aspects of the aerosol time evolution appear to be consistent with other observations and model predictions. Quantitative differences exist between inferred SME and lidar extinction coefficients, possibly due to the different wavelengths of the measurements and to the different scattering phase functions used in the two analyses. It is also shown that visible limb radiances provide information on the planetary albedo, which shows an increase from the equator to the poles with a maximum in the winter hemisphere and a minimum in the summer hemisphere.

NO2 was measured in the stratosphere at night by means of a balloon‐borne spectrometer, pointing at a bright rising star, in the 427 to 452 nm range. The vertical distribution of NO2 was deduced using the tangent ray technique between 23 and 38 km. The concentration was (6±1.5)×109 mol.cm−3 at 25 km, passing through a minimum of (2±1)×109 mol.cm−3 at 29 km and rising again up to (4±0.8)×109 mol.cm−3 at 32 km.