HYDROGEN RADICALS, NITROGEN RADICALS, AND THE PRODUCTION OF O-3 IN THE UPPER TROPOSPHERE

The concentrations of the hydrogen radicals OH and HO2 in the middle a nd upper troposphere were measured simultaneously with those of NO, O- 3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet an d visible radiation field. The data allow a direct examination of the processes that produce O-3 in this region of the atmosphere. Compariso n of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical co ncentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphe re may provide the source of HOx required to sustain the measured abun dances of these radical species. The mechanism by which NO affects the production of O-3 is also illustrated by the measurements. In the upp er tropospheric air masses sampled, the production rate for ozone (det ermined from the measured concentrations of HO2 and NO) is calculated to be about I part per billion by volume each day. This production rat e is faster than previously thought and implies that anthropogenic act ivities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O-3 than expected.