Simultaneous spectroscopic determination of the latitudinal, seasonal, and diurnal variability of stratospheric N2O, NO, NO2, and HNO3

Abstract

The importance Of NOx compounds to stratospheric chemistry has been clearly established. We report below on a program to measure latitudinal, seasonal, and diurnal variations in stratospheric N2O, NO, NO2, and HNO3 amounts. Through the use of airborne Fourier transform absorption spectroscopy, we determine simultaneously column amounts above 12 km of the four molecules listed above. Nitrous oxide (N2O) is found to have a fairly uniform distribution with latitude and season, with a stratospheric column abundance of 8.1 × 1017 molecules cm−2. Nitric oxide (NO) amounts are shown to decrease with increasing latitude in winter. A 50% decrease in high latitude winter amounts is observed as compared with low latitude values near 3.0 × 1015 molecules cm−2. Nitrogen dioxide (NO2) stratospheric amounts increase in summer with increasing latitude. Equatorial values are near 3.0 × 1015 molecules cm−2 above 12 km. A factor of 3–4 increase in higher latitude summertime NO2, as compared to winter NO2, is observed. Nitric acid (HNO3) amounts show a general increase toward higher latitudes and a marked increase in mid‐latitude winter as compared to summer. Winter amounts may be highly variable with a value near 1.0 × 1016 molecules cm−2.