REACTIVE NITROGEN AND ITS CORRELATION WITH OZONE IN THE LOWER STRATOSPHERE AND UPPER TROPOSPHERE

Reactive nitrogen (NO(y)) and O3 were measured simultaneously from a NASA ER-2 aircraft during 1987 through 1989. These high resolution measurements cover a broad range of latitudes in the upper troposphere and lower stratosphere. The data show a striking positive correlation between NO(y) and O3 in the lower stratosphere at all scales sampled. The ratio NO(y)/O3 is nearly independent of altitude from the tropopause to above 20 km, with ratios in the stratosphere of 0.0015-0.002 in the tropics and 0.0025-0.004 elsewhere. The ratio is much more constant than either individual species, thus providing an excellent reference point for comparing limited data sets with models. Two-dimensional models reproduce general features of the vertical profile of NO(y)/O3 but not the gradient in the lower stratosphere between tropics and mid-latitudes. NO(y) and O3 are better correlated in the lower stratosphere than in the upper troposphere. The magnitude and variability of both NO(y) mixing ratios and NO(y)/O3 ratios indicate a source of NO(y) in the upper troposphere. The most plausible source in the tropics is lightning production of NO(x). Condensation of NO(y) onto aerosol particles is often possible in the tropical upper troposphere and may play a role in determining the vertical distribution of NO(y). In the mid-latitude upper troposphere the data suggest long-range transport of NO(y). NO(y) mixing ratios in the tropical upper troposphere were usually between 150 and 600 pptv, enough so that upward transport can affect the NO(y) abundance in the tropical lower stratosphere.