Simultaneous measurements of H2O, NO2 and HNO3 in the daytime stratosphere from 15 to 35 km

Initial results are reported for two daytime high-altitude balloon flights that were undertaken to measure concentrations of H2O, HNO3, NO2, and several other trace gases with far-IR Michelson interferometers. The primary aim of the experiment was to investigate the concentrations of several gases simultaneously by using the wide-bandwidth and high-resolution capabilities of the Fourier technique. The results for H2O show a gradual increase in volume mixing ratio from about 3.0 ppm (by volume) at 15 km to about 5.5 ppm at 33 km. For NO2, the mixing ratio was found to increase from about 4 ppb at 25 km to about 18 ppb at 33 km, with some evidence of a maximum at this level. For HNO3, a pronounced maximum was observed at about 25 km, with a mixing ratio of about 9 ppb. These results are compared with those of previous measurements, and several variations are pointed out.