MEASUREMENTS OF REACTIVE NITROGEN COMPOUNDS IN THE FREE TROPOSPHERE

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Abstract

NO, NO2 and total reactive nitrogen, NOy, were measured using chemiluminescence throughout the troposphere. Flights were made from Frankfurt (West Germany) to Abu Dhabi (United Arab Emirates), and from Frankfurt to Sao Paulo (Brazil). NOx (NO + NO2) concentrations were determined with a FeSO4 converter and NOy with a 425°C Mo converter. NOx levels over the Northern Hemisphere at 9 km altitude were about 200 ppt. On one flight over central Europe the aircraft encountered a thunderstorm system over an area 600 km wide. NOy was markedly elevated in the area of these thunderstorms due, we believe, to the rapid transport of polluted boundary layer air into the upper troposphere. The long lifetime of these trace gases in the upper troposphere allows them to be transported to the remote atmosphere where photolysis and radical reactions could produce significant quantities of ozone. The NOy concentration of 3.5 () ppb was significantly higher than the concentration of about 190 ppt measured on a separate flight. These and NOx data indicate that tropospheric reactive nitrogen species vary widely in concentration, and a ‘representative’ distribution may not exist.

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