HR: 10:20h
AN: A22C-01 INVITED     [Abstracts]
TI: An assessment of the HOx budget constrained by Summit 2003 field observations
AU: * Chen, G
AF: NASA Langley Research Center, Mail Stop 401B, Hampton, VA 23681
AU: Crawford, J H
AF: NASA Langley Research Center, Mail Stop 401B, Hampton, VA 23681
AU: Huey, L G
AF: Georgia Institude of Technology, 311 Ferst Drive, Atlanta, GA 30332
AU: Tanner, D
AF: Georgia Institude of Technology, 311 Ferst Drive, Atlanta, GA 30332
AU: Sjostedt, S
AF: Georgia Institude of Technology, 311 Ferst Drive, Atlanta, GA 30332
AU: Dibb, J
AF: University of New Hampshire, 39 College Road, Durham, NH 03824
AU: Hutterli, M A
AF: University of Arizona, 1133 E. North Campus Dr., Tucson, AZ 85721
AU: Lefer, B
AF: University of Houston, 4800 Calhoun Road, Houston, TX 77204
AU: Shetter, R
AF: National Center for Atmospheric Research, 1850 Table Mesa DR, Boulder, CO 80305
AU: Blake, N
AF: University of California, Irvine, 573 Rowland Hall, Irvine, CA 92697
AU: Blake, D
AF: University of California, Irvine, 573 Rowland Hall, Irvine, CA 92697
AU: Beyersdorf, A
AF: University of California, Irvine, 573 Rowland Hall, Irvine, CA 92697
AU: Sueper, D T
AF: NOAA Aeronomy Laboratory, R/AL7, 325 Broadway, Boulder, CO 80305
AB: The first observations of HOx at Summit, Greenland have shown elevated summertime values of OH and HO2 which are significantly higher than those measured in the South Pole (SP). The high levels of SP OH are believed to be the effect of the enhanced levels of NO, averaging from 100 to 200 pptv, from snow emissions. In the case of Summit, however, the NO averages are about 5 to 10 times lower those of SP. To better understand the sources and sinks HOx in snow covered polar region, the Summit HOx budget is compared to that of SP. The Summit HOx budget analysis is based on model calculations constrained by in-situ observations of precursors made in early July of 2003. This is a period, characterized by relatively calm wind, when model predicted HO2 is in close agreement with observations. Model estimated OH levels, however, are about 2 times lower than the observations. Summit summertime (early July) ambient temperature and dew point are, on average, about 10 and 20 degrees higher those of SP (December averages), respectively. As a result of these differences, the reaction of O(1D) + H2O is estimated to be the largest HOx source, instead of CH4 oxidation as concluded in SP studies. Contributions from snow emissions of HOx precursors, especially HONO, are significant but relatively less important for Summit than for SP. Calculations are carried out to evaluate the sensitivities of the total HOx source and sink to each of the snow emitted precursors. As for the HOx losses, the reaction of OH + NO2, like in SP, remains to be the major loss pathway. By contrast, loss through formation of HO2NO2 is much less significant in Summit due to the higher ambient temperature. The potential impact of halogen chemistry on Summit HOx budget is also evaluated. Finally, the consequence of Summit HOx chemistry is evaluated in terms of its impact on NOx lifetime and ozone levels.
DE: 9315 Arctic region
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0317 Chemical kinetic and photochemical properties
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting