Springtime photochemistry at northern mid and high latitudes

Yuhang Wang, Brian Ridley, Alan Fried, Christopher Cantrell, Douglas Davis, Gao Chen, Julie Snow, Brian Heikes, Robert Talbot, Jack Dibb, Frank Flocke, Andrew Weinheimer, Nicola Blake, Donald Blake, Richard Shetter, Barry Lefer, Elliot Atlas, Michael Coffey, Jim Walega, Brian Wert

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


Physical and chemical properties of the atmosphere at 0-8 km were measured during the Tropospheric Ozone Production about the Spring Equinox (TOPSE) experiments from February to May 2000 at mid (40°-60°N) and high latitudes (60°-80°N). The observations were analyzed using a diet steady state box model to examine HOx and O3 photochemistry during the spring transition period. The radical chemistry is driven primarily by photolysis of O3 and the subsequent reaction of O(1D) and H2O, the rate of which increases rapidly during spring. Unlike in other tropospheric experiments, observed H2O2 concentrations are a factor of 2-10 lower than those simulated by the model. The required scavenging timescale to reconcile the model overestimates shows a rapid seasonal decrease down to 0.5-1 day in May, which cannot be explained by known mechanisms. This loss of H2O2 implies a large loss of HOx resulting in decreases in O3 production (10-20%) and OH concentrations (20-30%). Photolysis of CH2O, either transported into the region or produced by unknown chemical pathways, appears to provide a significant HOx source at 6-8 km at high latitudes. The rapid increase of in situ O3 production in spring is fueled by concurrent increases of the primary HOx production and NO concentrations. Long-lived reactive nitrogen species continue to accumulate at mid and high latitudes in spring. There is a net loss of NOx to HNO3 and PAN throughout the spring, suggesting that these long-term NOx reservoirs do not provide a net source for NOx in the region. In Situ O3 chemical loss is dominated by the reaction of O3 and HO2, and not that of O(1D) and H2O. At midlatitudes, there is net in situ chemical production Of O3 from February to May. The lower free troposphere (1-4 km) is a region of significant net O3 production. The net production peaks in April coinciding with the observed peak of column O3 (0-8 km). The net in situ O3 production at midlatitudes can explain much of the observed column O3 increase, although it alone cannot explain the observed April maximum. In contrast, there is a net in situ O3 loss from February to April at high latitudes. Only in May is the in situ O3 production larger than loss. The observed continuous increase of column O3 at high latitudes throughout the spring is due to transport from other tropospheric regions or the stratosphere not in situ photochemistry.

Original languageEnglish (US)
Pages (from-to)6-1 - 6-32
JournalJournal of Geophysical Research: Atmospheres
Issue number4
StatePublished - Feb 27 2003
Externally publishedYes


  • Oxidation
  • Ozone
  • Reactive nitrogen
  • Springtime

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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