On the origin of tropospheric ozone and NOx over the tropical South Pacific

Martin G. Schultz, Daniel J. Jacob, Yuhang Wang, Jennifer A. Logan, Elliot L. Atlas, Donald R. Blake, Nicola J. Blake, John D. Bradshaw, Edward V. Browell, Marta A. Fenn, Frank Flocke, Gerald L. Gregory, Brian G. Heikes, Glen W. Sachse, Scott T. Sandholm, Richard E. Shetter, Hanwant B. Singh, R. W. Talbot

Research output: Contribution to journalArticlepeer-review

122 Scopus citations


The budgets of ozone and nitrogen oxides (NOx = NO + NO2) in the tropical South Pacific troposphere are analyzed by photochemical point modeling of aircraft observations at 0-12 km altitude from the Pacific Exploratory Mission-Tropics A campaign flown in September-October 1996. The model reproduces the observed NO2/NO concentration ratio to within 30% and has similar success in simulating observed concentrations of peroxides (H2O2, CH3OOH), lending confidence in its use to investigate ozone chemistry. It is found that chemical production of ozone balances only half of chemical loss in the tropospheric column over the tropical South Pacific. The net loss is 1.8 x 1011 molecules cm-2 s-1. The missing source of ozone is matched by westerly transport of continental pollution into the region. Independent analysis of the regional ozone budget with a global three-dimensional model corroborates the results from the point model and reveals the importance of biomass burning emissions in South America and Africa for the ozone budget over the tropical South Pacific. In this model, biomass burning increases average ozone concentrations by 7-8 ppbv throughout the troposphere. The NOx responsible for ozone production within the South Pacific troposphere below 4 km can be largely explained by decomposition of peroxyacetylnitrate (PAN) transported into the region with biomass burning pollution at higher altitudes.

Original languageEnglish (US)
Article number98JD02309
Pages (from-to)5829-5843
Number of pages15
JournalJournal of Geophysical Research Atmospheres
Issue numberD5
StatePublished - Mar 20 1999
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology


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