Nicole Louisnard

Vertical Distribution of NO, NO 2 , and HNO 3 as Derived from Stratospheric Absorption Infrared Spectra

This paper is devoted to the results concerning NO, NO(2), and HNO(3) obtained during airborne experiments performed in June-July 1973 on Concorde 001. The altitude of flight was about 16 km. Results concerning NO are, within the accuracy of measurement, in agreement with results of a previousspectrometric balloonborne experiment conducted jointly by IASB and ONERA (14 May 1973). Nitric oxide is concentrated in stratospheric layers clearly above the flight altitude. Integrated amount of NO along the optical path is (4 +/- 1.5) x 10(16) mol cm(-2) for a solar elevation varying from +2 degrees above the horizontal plane to -1 degrees . A value of 6 x 10(8) mol cm(-3) may be given as an upper limit for the local concentration at the flight altitude. Thereis no significant difference in the integrated amount observed at sunset and sunrise. Measured value of NO(2) local concentration at 15.5 km is (1.1 +/- 0.2) x 10(9) mol cm(-3), in sunset conditions. This value is not greatly modified between 15 km and 30 km. Measured value of HNO(3). This value increases with altitude between 15 km and 20 km. The local concentration is maximum at 20 km. The measured value is (2 +/- 1) x 10(10) mol cm(-3) at 20 km. It seems that local concentration decreases rapidly above 20 km.

Infrared absorption spectroscopy applied to stratospheric profiles of minor constituents

Infrared absorption by O3, NO, NO2, N2O, HNO3, CO, COS, CH4 and H2O have been observed from a balloon platform at 40 km of altitude and 44°N latitude with a grille spectrometer. The resolution is, for the most part, better than 0.1 cm−1. An analysis is made of the causes of uncertainties. Height profiles are deduced for these species down to 20 km. The mixing ratios near 40 km are 8.5±1.5 ppm for ozone, 8. ±1 ppm for water vapor, and 19±5 ppb for carbon monoxide. Nitric acid and carbonyl sulfide exhibit a decreasing profile with altitude. Mixing ratios near 30 km are <10–10 for COS and 8±1 ppb for HNO3. Some common observations are made, related to the particular temperature profile, which emphasize the importance of simultaneous measurements of stratospheric species and meteorological parameters.