SAGE observations of stratospheric nitrogen dioxide

Abstract

The global distribution of nitrogen dioxide in the middle to upper stratosphere (25–45 km altitude) for the period Feburary 1979 to November 1981 has been determined from observations of attenuated solar radiation in the visible region 0.385–0.45 μm by the Stratospheric Aerosol and Gas Experiment (SAGE) satellite instrument. The SAGE‐derived NO2 vertical profiles compare well with observations by balloon and aircraft‐borne sensors. The global SAGE NO2 distributions generally show a maximum in mixing ratio of 8 parts per billion by volume at about 35 km altitude near the equatorial latitudes at local sunset. The location of the mixing ratio peak moves synchronously with the overhead sun for the four different seasons. High‐latitude NO2 column content shows strong seasonal variation, with a maximum in local summer and a minimum in local winter. Selected data at high‐latitude winter seasons are presented, suggesting that the large variation shown could be explained by the coupling of both dynamics and photochemistry of the NOx species. Finally, profiles of the ratio of sunset to sunrise NO2 mixing ratios, peaking at about a factor of 2 at 30 km, are shown.