Peroxyacetyl nitrate measurements during CITE 2: Atmospheric distribution and precursor relationships

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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 95, NO. D7, PAGES 10,163–10,178, 1990 Peroxyacetyl nitrate measurements during CITE 2: Atmospheric distribution and precursor relationships H. B. Singh NASA Ames Research Center, Moffett Field, California E. Condon NASA Ames Research Center, Moffett Field, California J. Vedder NASA Ames Research Center, Moffett Field, California D. O’Hara San Jose State University Foundation, Moffett Field, California B. A. Ridley National Center for Atmospheric Research, Boulder, Colorado B. W. Gandrud National Center for Atmospheric Research, Boulder, Colorado J. D. Shetter National Center for Atmospheric Research, Boulder, Colorado L. J. Salas SRI International, Menlo Park, California B. Huebert SRI International, Menlo Park, California G. Hübler NOAA Aeronomy Laboratory, Boulder, Colorado M. A. Carroll NOAA Aeronomy Laboratory, Boulder, Colorado D. L. Albritton NOAA Aeronomy Laboratory, Boulder, Colorado D. D. Davis Georgia Institute of Technology, Atlanta J. D. Bradshaw Georgia Institute of Technology, Atlanta S. T. Sandholm Georgia Institute of Technology, Atlanta M. O. Rodgers Georgia Institute of Technology, Atlanta S. M. Beck NASA Langley Research Center, Hampton, Virginia G. L. Gregory NASA Langley Research Center, Hampton, Virginia P. J. LeBel NASA Langley Research Center, Hampton, Virginia Abstract Aircraft measurements of peroxyacetyl nitrate (PAN) and other important reactive nitrogen species (NO, NO₂, HNO₃, and NO_y) were performed over the continental United States and the eastern Pacific during August-September 1986 at all altitudes between 0 and 6 km as part of CITE 2. PAN measurements were conducted by two independent groups, allowing both intercomparisons and greater confidence in its observed atmospheric structure. PAN was found to be a dominant reactive nitrogen species in the troposphere with 98% of the mixing ratios falling in a range of 5–400 ppt. Typically, the highest mixing ratios (100–300) ppt were observed aloft (4–6 km) with extremely low values (5–20 ppt) in the marine boundary layer. In the lower troposphere. Continental air contained siginficantly more PAN than marine air. The vertical structure of PAN was largely dictated by its thermal destruction rate and equilibrium with available NO₂. PAN mixing ratios showed a high degree of variability in both continental and marine atmospheres. Westerly marine air trajectories did not guarantee well-mixed air of uniform composition. Mixing ratios of O₃, NO_y, NO_x, HNO₃, C₂H₆, CO, and CFCl₃ were strongly correlated with those of PAN, indicating the important role played by transport processes. High PAN to NO_x ratios in the mid-troposphere further support the importance of long-range transport from continental sources. Frequently, descending air masses from the upper troposphere suggested that PAN mixing ratios probably continued to increase above the 6-km ceiling altitude. Air masses with O₃<20 ppb, CO<60 ppb, and C₂H₆<500 ppt contained only miniscule amounts of PAN and are expected to be of tropical origin. Reasons for the observed PAN variability, are discussed. © American Geophysical Union 1990 Index Terms: 4825 Oceanography: Biological and Chemical: Geochemistry. Citation: Singh, H. B., et al. (1990), Peroxyacetyl nitrate measurements during CITE 2: Atmospheric distribution and precursor relationships, J. Geophys. Res., 95(D7), 10,163–10,178. Copyright 1990 by the American Geophysical Union.

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