During a further flight of the Oxford balloon-borne pressure modulator radiometer, altitude profiles of NO and NO2 were measured simultaneously from mid-morning till sunset. An improved detector for the NO channel, a better procedure for interpolating between calibration points, and an improved error analysis yielded results of higher quality than from previous flights. During the day the NO2 column above 24 km increased by 0.42 ± 0.28 to 1.86 ± 0.24 × 1015 molecule cm-2 the NO column above 30 km reached a maximum of 5.2 ± 1.3 × 1015 molecule cm-2 soon after noon, falling by 1.58 ± 0.77 × 1015 molecule cm-2 by an hour before sunset. A detailed comparison of measured NO and NO2 concentrations with those predicted by the Oxford two-dimensional diurnal model shows disagreement in their absolute values but close agreement in their daytime changes. The model predicts a fall in NO during the afternoon, as observed.
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Roscoe et al. (1981) studied this question.