Measurements of nitric oxide in the stratosphere of the Southern Hemisphere

Vertical profiles of NO in the stratosphere above Mildura, Australia (34°S, 142°E), were obtained in December 1977 using a balloon‐borne chemiluminescent detector. The average mixing ratio increased from about 0.2 ppbv at 10 km to 0.45 at 20 km and to about 7 ppbv at 33 km. The results are in good agreement with a profile obtained in the USA (32°N, 96°W) during October 1977 with the same instrument. It is suggested that the stratospheric NO distribution may, at low latitudes, be symmetric about the equator. The NO measurements and earlier chemical‐filter HNO3 measurements made at Mildura are compared to recent chemical model predictions.