Instantaneous global nitrous oxide photochemical rates

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Abstract
In recent years, vertical profiles of nitrous oxide have been measured by balloon up to midstratosphere at several latitudes between 63°N and 73°S, including one profile in the tropical zone at 9°N. Two rocket flights measured nitrous oxide mixing ratios at 44 and 49 km. From these experimental data plus a large amount of interpolation and extrapolation, we have estimated a global distribution of nitrous oxide up to the altitude of 50 km. With standard global distributions of oxygen and ozone we carried out instantaneous, three‐dimensional, global photochemical calculations, using recently measured temperature‐dependent cross sections for nitrous oxide. The altitude of maximum photolysis rate Of N2O is about 30 km at all latitudes, and the rate of photolysis is a maximum in tropical latitudes. The altitude of maximum rate of formation of nitric oxide is latitude dependent, about 26 km at the equator, about 23 km over temperate zones, and 20 km at the summer pole. The global rate of N2O destruction is 6.2×1027 molecules s−1, and the global rate of formation of NO from N2O is 1.4×1027 molecules s−1. The global N2O inventory divided by the stratospheric loss rate gives a residence time of about 175 years with respect to this loss process. From the global average N2O profile a vertical eddy diffusion profile was derived, and this profile agrees very closely with that of Stewart and Hoffert (1975).