Simultaneous in situ measurements of nitrogen dioxide, nitric oxide, and ozone between 20 and 31 km

Simultaneous in situ measurements of NO, NO 2 , O 3 , and temperature were made from approximately 20 to 31 km in the stratosphere during July, August, and November. Two of the balloon flights were made from Palestine, Texas (32°N), the third from Gimli, Manitoba (50°N). NO was detected using the chemiluminescence technique; NO 2 was photolyzed to NO prior to detection. Both the NO and NO 2 mixing ratios are in good agreement with most other measurements in this altitude region. To within the combined uncertainties the measured NO 2 to NO ratios agree with those calculated assuming photochemical steady state. There is, however, a tendency for the observed ratio to be larger than the calculated ratio at low altitudes near 32°N, but not at 50°N. Refinements to the experiment will be required to elucidate unequivocal discrepancies. From the observation of a temporal increase in the sum of NO and NO 2 while at constant altitude, it is possible to infer the abundance of N 2 O 5 near noon. Further, a lower‐limit estimate of the total odd nitrogen mixing ratio of 16–19 parts per billion by volume near 30 km is made using the observations of NO x , the estimated N 2 O 5 mixing ratio, and previous measurements of HNO 3 .