HR: 17:30h
AN: A24A-06    [Abstracts]
TI: Halogen-Driven Low Altitude Ozone and Hydrocarbon Losses in Spring at Northern High Latitudes
AU: * Zeng, T
EM: tzeng@eas.gatech.edu
AF: Georgia Institute of Technology, 311 Ferst Drive, EAS, Atlanta, GA 30332 United States
AU: Wang, Y
EM: ywang@eas.gatech.edu
AF: Georgia Institute of Technology, 311 Ferst Drive, EAS, Atlanta, GA 30332 United States
AU: Chance, K
EM: kchance@cfa.harvard.edu
AF: Harvard-Smithsonia Center for Astrophysics, Atomic and Molecular Physics Division 60 Garden Street, Cambridge, MA 02138 United States
AU: Blake, N
EM: nblake@uci.edu
AF: University of California at Irvine, Department of Chemistry, Irvine, CA 92697 United States
AU: Blake, D
EM: drblake@uci.edu
AF: University of California at Irvine, Department of Chemistry, Irvine, CA 92697 United States
AU: Ridley, B
EM: ridley@ucar.edu
AF: NCAR, Atmospheric Chemistry Division, Boulder, CO 80307 United States
AB: Halogen-driven ozone and hydrocarbon losses in springtime Arctic boundary layer are investigated using a regional chemical transport model. Surface observations of ozone at Alert, Canada and Barrow, Alaska and aircraft observations of ozone and hydrocarbons during the Tropospheric Ozone Production about the Spring Equinox (TOPSE) experiment from February to May in 2000 are analyzed. We prescribe halogen radical distributions in the surface layer of 300m on the basis of GOME BrO observations. GOME BrO shows an apparent anti-correlation with surface temperature over high BrO regions. While GOME BrO measurements reach the maximum in March, simulated near-surface ozone loss peaks in April due to the increasing daylight hours and hence the time for chemical processes. At its peak, the area of simulated near-surface ozone depletions (O₃ < 20 ppbv) covers >50% of the northern high latitudes. Model simulated ozone losses are in reasonable agreement with surface ozone observations at Alert and Barrow and seasonal trends of low ozone concentrations from aircraft measurement during TOPSE. Further constraints on simulated halogen distributions are investigated using aircraft hydrocarbon measurements. There is evidence that the currently accepted chemical mechanism significantly overestimates the Cl/BrO ratios. When the empirical ratios derived from previous observations are used, the model can reproduce the observed halogen loss of light alkanes and acetylene. We find that the hydrocarbon loss is not as sensitive to the prescribed thickness of the halogen layer as ozone loss, therefore representing a more robust measure for evaluating satellite column measurements.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005